GREEN ROOFTOP SYSTEMS: A SOUTH AFRICAN PERSPECTIVE 
 
 
PETRONELLA HENDRINA LABUSCHAGNE 
 
 
Submitted in fulfilment of the requirements in respect of the Master’s Degree qualification in 
Quantity Surveying in the Department of Quantity Surveying and Construction Management 
in the Faculty of Natural and Agriculture Sciences at the University of the Free State. 
 
29 February 2016 
Study Leader: Dr. B.G. Zulch 
 
 
 
 
 
 
 
 
 
 
 
TABLE OF CONTENTS 
TABLE OF CONTENTS         i 
APPROVAL           v 
DECLARATION          vi 
ACKNOWLEDGEMENTS         vii 
ABSTRACT           viii 
LIST OF TABLES          x 
LIST OF FIGURES          xi 
 
CHAPTER 1: INTRODUCTION TO STUDY 
1.1. Title           1 
1.2. Introduction          1 
1.3. The rationale          1 
1.4. Problem statement         2 
1.5. Hypothesis          2 
1.6. Theoretical framework and objective       2 
1.7. Research methodology         3 
1.8. Chapter outlay          3 
 
CHAPTER 2: INTRODUCTION TO GREEN ROOFTOP GARDENS 
2.1 Introduction          5 
2.2 The history of green rooftop gardens       5 
2.3 Green rooftop systems         7 
2.3.1 Vegetation          7 
2.3.2 Planting medium         8 
2.3.3 Containment         8 
2.3.4 Drain layer          9 
2.3.5 Protective layer         9 
2.3.6 Insulation          9 
2.3.7 Waterproofing         10 
2.3.8 Irrigation          10 
2.4 Types of rooftop systems         10 
2.4.1 Extensive green rooftops        11 
2.4.2 Semi-intensive green rooftops       13 
2.4.3 Intensive green rooftops        15 
2.4.4 Modular rooftop system        18 
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2.5 Conclusion          20 
 
CHAPTER 3: THE EFFECT OF GREEN ROOFTOPS IN CITIES 
3.1 Introduction          22 
3.2 Energy savings          22 
3.3 Life extension of the roof membrane       24 
3.4 Sound insulation          25 
3.5 Fire resistance          26 
3.6 Storm water management        26 
3.7 Urban heat island effect         27 
3.8 Creation and preservation of habitat and ecological biodiversity   31 
3.9 Aesthetics and recreational space       33 
3.10 Urban agriculture         34 
3.11 Creating jobs          35 
3.12 Subsidizing green rooftop systems       35 
3.13 National building regulations        35 
3.14 Money as a motivator         35 
3.15 Air quality          36 
3.15.1 Air quality index         36 
3.15.2 The air quality index of Johannesburg      37 
3.15.3 The causes of the poor air quality in Johannesburg    40 
3.15.4 Cleaning the air with vegetation       41 
3.16 Conclusion          41 
 
CHAPTER 4: CONSTRUCTING GREEN ROOFTOPS 
4.1 Introduction          43 
4.2 Location and climate         43 
4.3 Weight loading          45 
4.4 Consultants          46 
4.5 Drainage           47 
4.6 Access           50 
4.7 Constructing the different layers with materials available in South Africa  50 
4.7.1 Layer 1: Waterproofing        50 
4.7.2 Layer 2: Root Barrier        51 
4.7.3 Layer 3: Drainage layer        52 
4.7.4 Separation and additional root barrier layer     53 
4.7.5 Layer 5: Growing medium        54 
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4.8 Communication, negotiation and persuasion of implementation    55 
4.9 Public buildings as an example for green rooftop systems    56 
4.10 Conclusion          57 
 
CHAPTER 5: PLANTS SUITABLE FOR GREEN ROOFS IN SOUTH AFRICA 
5.1 Introduction          58 
5.2 The types of species that are suitable for growing on rooftops in South Africa  58 
5.2.1 Cassinopsis Ilicifolia (Hochst.)       58 
5.2.2 Eucomis autumnalis (Mill.) Chitt      59 
5.2.3 Portulacaria afra (Jacq.)       60 
5.2.4 Aloe maculata          61 
5.2.5 Aloe arborescens         61 
5.2.6 Asparagus densiflorus        62 
5.2.7 Aleollanthus parvifolius        63 
5.2.8 Agapanthus inapertus P.Beauv.      63 
5.2.9 Crassula ovata         64 
5.2.10 Crassula Expansa        65 
5.2.11 Albuca Setosa         65 
5.2.12 Bulbine narcissifolia        66 
5.2.13 Eulophia speciosa        67 
5.2.14 Delosperma lineare        67 
5.2.15 Delosperma tradescantioides       68 
5.2.16 Gladiolus dalenii        68 
5.2.17 Plectranthus Spicatus        69 
5.2.18 Crytanthus Sanguineus        70 
5.2.19 Kalanchoe thyrsiflora        71 
5.2.20 Cyanotis Speciosa        71 
5.3 Plants suitable for roofs in Johannesburg      72 
5.4 Conclusion          74 
 
CHAPTER 6: RESEARCH DESIGN AND METHODOLOGY 
6.1 Introduction          75 
6.2 Research strategy         76 
6.3 Methodology          76 
6.3.1 Questionnaire survey        76 
6.3.2 Field notes         77 
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6.4 Conclusion          77 
 
CHAPTER 7: FIELD NOTES - ROOFS IN JOHANNESBURG 
7.1 Introduction          78 
7.2 Roofs in Johannesburg CBD        78 
7.3 Green rooftop systems in Johannesburg       79 
7.4 Conclusion          83 
 
CHAPTER 8: EMPIRICAL STUDY IN GREEN ROOFTOP SYSTEMS IN SOUTH AFRICA 
8.1 Introduction          84 
8.2 Empirical data          84 
8.2.1 Profile of respondents       84 
8.2.2 Section 1 Empirical Data       85 
8.2.3 Section 2 Empirical Data       90 
8.2.4 Section 3 Empirical Data       95 
8.2.5 Section 4 Empirical Data       99 
8.3 Conclusion          101 
 
CHAPTER 9: CONCLUSION AND RECOMMENDATION 
9.1 Introduction          104 
9.2 Summary of study          104 
9.3 Findings           105 
9.3.1 First hypothesis         105 
9.3.2 Second hypothesis        105 
9.3.3 Third hypothesis        106 
9.3.4 Fourth hypothesis        106 
9.4 Conclusion          107 
9.5 Recommendations for further research       107 
9.5.1 Recommendations for industry       107 
9.5.1 Recommendations for further research     108 
 
REFERENCES           109 
ANNEXURE A – QUESTIONNAIRE        121 
 
 
 
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APPROVAL 
 
 
 
 
 
 
 
The thesis of Petronella Hendrina Labuschagne is approved by 
 
 
 
Signed:…………………………………………..…      Date:……..………………………………. 
Dr. B.G. Zulch (Programme Director, Senior Lecturer and Study leader) 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
v 
 
DECLARATION 
 
(i) “I, Petronella Hendrina Labuschagne, declare that the Master’s Degree research 
dissertation or interrelated, publishable manuscripts/published articles, or coursework 
Master’s Degree mini-dissertation that I herewith submit for the Master’s Degree qualification 
in Quantity Surveying at the University of the Free State is my independent work, and that I 
have not previously submitted it for a qualification at another institution of higher education.” 
 
(ii) “I, Petronella Hendrina Labuschagne, hereby declare that I am aware that the copyright is 
vested in the University of the Free State.” 
 
(iii) “I, Petronella Hendrina Labuschagne, hereby declare that all royalties as regards 
intellectual property that was developed during the course of and/or in connection with the 
study at the University of the Free State, will accrue to the University.” 
 
 
 
 
 
Signed:………………………………………..……        Date: ……………………………… 
            Petronella Hendrina Labuschagne 
 
 
 
 
 
 
 
 
 
 
 
vi 
 
ACKNOWLEDGEMENTS 
A research project of this magnitude cannot be achieved without the support and guidance 
from other people.  I wish therefore to acknowledge the support and guidance given to me in 
carrying out this research project by a number of individuals. 
Firstly, I wish to express my gratitude to my promoter Dr B.G. Zulch for her guidance through 
every stage of the research project. 
Secondly, my thanks go to the entire staff of the Department of Quantity Surveying and 
Construction Management for the effort done by them in order for me to complete the 
research. 
Thirdly, I wish to thank all my friends and relatives for the encouragement and support given 
throughout the research project. 
Lastly but not least, I would like to thank my mom, Drina Labuschagne, for all her help, 
support and enthusiasm towards this research project.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
vii 
 
ABSTRACT 
Title of thesis   : Green rooftop systems: A South African perspective  
Name of author   : Petronella Hendrina Labuschagne 
Name of Study Leader  : Dr B.G. Zulch 
Institution   : Faculty of Natural and Agricultural Sciences 
Department of Quantity Surveying and Construction 
Management 
University of the Free State 
Bloemfontein, South Africa 
Date    : February 2016 
 
The purpose of this study is to determine the outcome of green rooftop systems in South 
Africa.  Cities in South Africa are expanding with new developments.  With development and 
expansion comes the increase in pollutants, undesirable living conditions and challenges to 
overcome.  Rooftop gardens are not getting the recognition for the value of it to the 
environment, the citizens, the industry and the buildings as such in South Africa.  This is due 
to lack of knowledge and innovation.  Green rooftop systems is a relatively new concept in 
South Africa.   
The study used a literature review followed by field notes and 68 questionnaires received 
back from contractors, quantity surveyors, engineers, architects and citizens of 
Johannesburg. 
The respondents do not have experience regarding the construction of green rooftop 
systems, and thus indicates why professional members of the construction industry do not 
recommend the development thereof.  This further indicates that there is a lack of knowledge 
in the industry regarding the construction of green rooftop systems and the benefits that 
accompanies green rooftop systems.  Despite the lack of knowledge in the industry, the 
materials needed to construct green rooftop systems are available in South Africa.   
Johannesburg seems to benefit most from improved air quality and better insulated 
buildings.  Other benefits also includes job creation, aesthetics, eliminating the heat island 
effect, stormwater management and economic growth.  Respondents do not utilise existing 
green areas due to crime and unsafeness and green rooftop systems provide a secure and 
viii 
 
safe green area.  Green areas also provide health benefits such as promotion of health, 
reducing stress, depression and anxiety.  
Drainage and structural integrity seems to be important factors that may limit the 
development of green rooftop systems due to the financial impact.  Incentives seem to be 
the best way to encourage the development of green rooftop systems according to the 
respondents.  Therefore finance is a concern for the development of green rooftop systems 
in South Africa; however, there is a demand for it as the respondents are willing to pay more 
rent for property with green areas.  Property value thus increases with the development of 
green rooftop systems and absorbs the financial impact thereof.   
There are different types of green rooftop systems with different cost implications and 
according to the respondents, the semi-intensive green rooftop system will be feasible for 
South African circumstances.  The field notes presented that the few existing green rooftop 
systems in Johannesburg are semi-intensive green rooftop systems.  Green rooftop systems 
may conserve indigenous plant species and create habitats.   
In conclusion, Johannesburg will benefit from green rooftop systems, despite the capital 
cost.  The professionals in the construction industry do not have experience in the 
construction of green rooftop systems and have a lack of knowledge thereof, thus do not 
recommend the development of green rooftop systems to developers.   
The lack of knowledge regarding the construction of green rooftop systems and the benefits 
provided by green rooftop systems should be addressed, not only the construction industry, 
but also to the public. 
Keywords: Green rooftop systems in South Africa, the South African perspective of green 
rooftop systems, how to construct green rooftop systems, effects of green rooftop systems 
 
 
 
 
 
 
 
 
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LIST OF TABLES 
Table 2.1: Modular characteristics         18 
Table 2.2: Comparison of the main types of green rooftop systems    19 
Table 3.1: AQI Categories              36 
Table 3.2: City of Johannesburg ambient air quality guideline     39 
Table 4.1: Elements to consider when identifying the micro-climate    44 
Table 4.2: Weight loading as per vegetation type       45 
Table 5.1: Plants suitable for green rooftop systems in Johannesburg    73 
Table 8.1: Profile of respondents          84 
Table 8.2: Familiarity with green rooftop systems (Question 1.1)     85 
Table 8.3: Extensive green rooftop system in South Africa      87 
Table 8.4: Semi-Intensive green rooftop system in South Africa      88 
Table 8.5: Intensive green rooftop system in South Africa      89 
Table 8.6: Comparison of type of green rooftop systems      89 
Table 8.7: Factors influencing the development of green rooftop systems    91 
Table 8.8: Elements benefitting Johannesburg       92 
Table 8.9: Reasons for not utilizing parks        93 
Table 8.10: Health benefits from vegetated spaces       94 
Table 8.11: Experience in constructing green rooftop systems     96 
Table 8.12: Factors to consider when constructing a green rooftop system    97 
Table 8.13: Options to consider when water is a problem in South Africa    98 
Table 8.14: Factors limiting the development of green rooftop systems    98 
Table 8.15: Encouraging the development of green rooftop systems in South Africa 99 
Table 8.16: Preferred characteristics for rooftop plants      100 
Table 8.17: Preferred plants for rooftops        101 
 
 
 
 
 
 
 
 
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LIST OF FIGURES 
Figure 2.1: A section through an extensive rooftop system.     12 
Figure 2.2: An example of an extensive rooftop system.      13 
Figure 2.3: A section through a semi-intensive rooftop system.     14 
Figure 2.4: An example of a semi-intensive rooftop system.     15 
Figure 2.5: A section through an intensive green rooftop system.     16 
Figure 2.6: An example of an intensive green rooftop system.     17 
Figure 3.1: Fluctuation of daily temperatures of a conventional roof, ambient  
temperature, and a green roof.         24 
Figure 3.2: Sound attenuation by green roof comparing different frequencies and  
different substrate thicknesses.         25 
Figure 3.3: The heat island effect         28 
Figure 3.4: High and Low Albedo         30 
Figure 3.5:  Green rooftop systems mitigating the heat island effect    31 
Figure 3.6 Comparison of animals spotted on a green roof and blank roof.   32 
Figure 3.7: The different animal species spotted on the green rooftop system   33 
Figure 3.8: The 20 most polluted cities in the world       38 
Figure 4.1: A graphic illustration of different drainage systems     48 
Figure 4.2: Ponding           49 
Figure 4.3: Derbigum waterproofing membrane        51 
Figure 4.4: Black 250 micron (DPM) polythene sheeting      52 
Figure 4.5: Delta MS20P (perforated) polyethylene dimpled sheeting    52 
Figure 4.6: The installation of Bidim and the four joining methods     53 
Figure 4.7: Farming Kindergarten, Viëtnam        56 
Figure 5.1: Lemon thorn shrub         59 
Figure 5.2: Pineapple flower          59 
Figure 5.3: Porkbush           60 
Figure 5.4: Soap aloë          61 
Figure 5.5 Kranz Aloë          62 
Figure 5.6: Asparagus fern          62 
Figure 5.7: Klipsalie           63 
Figure 5.8: Drooping agapanthus         64 
Figure 5.9: Jade plant           64 
Figure 5.10: Crassula Expansa        65 
Figure 5.11: Slymstok          66 
Figure 5.12: Snake flower          66 
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Figure 5.13: Eulophia Speciosa         67 
Figure 5.14: Delosperma lineare         68 
Figure 3.15: Delosperma tradescantioides         68 
Figure 5.16: African Gladiolus         69 
Figure 5.17: Plectranthus Spicatus         70 
Figure 5.18: Cyrtanthus Sanguineus        70 
Figure 5.19: Kalanchoe thyrsiflora         71 
Figure 5.20: Cyanotis Speciosa         72 
Figure 7.1: Roofs of buildings in Johannesburg CBD      78 
Figure 7.2: Planter boxes on the DaVinci Hotel       79 
Figure 7.3: Relaxing space with green rooftop system on the DaVinci Hotel   80 
Figure 7.4: Green rooftop system on The Michealangelo hotel     81 
Figure 7.5: Green rooftop system on the Sandton Convention Centre    81 
Figure 7.6: Rooftop system on a residential house       82 
 
 
 
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CHAPTER 1: INTRODUCTION TO STUDY 
1.1 TITLE 
Green Rooftop Systems: A South African Perspective 
1.2 INTRODUCTION 
Cities in South Africa are expanding with new developments.  At the forefront of expansion is 
Johannesburg.  Between 2001 and 2011, the population of Johannesburg increased by an 
average of 121 000 annually.  An average number of 43 000 new homes were built every 
year over the same period.  Johannesburg is forecasted to double in size by 2040 (City of 
Johannesburg, 2012: 2).  With development and expansion comes an increase in pollutants 
(Momberg & Grant, 2008: Online).  A concern in the twenty first century is the continual 
decrease in air quality and the change of air composition.  South Africa is a developing 
country, which means that there are obstacles to overcome.  South Africa needs to learn 
with regards to controlling pollutants.  Countries such as China, Japan and the USA have 
had years of experience overcoming the problem of over populated cities and the pollution 
that comes with it.  South Africa should learn from the mistakes of experienced countries and 
the solutions that these countries have implemented in correcting mistakes.  A possible 
solution that may be implemented to combat increasing air pollution and unhealthy 
environment is the use of rooftop gardens (Miller, 2015: Online).  Rooftop gardens are used 
in Asia where population density is high, yet as South African cities expand and become 
denser, South Africa seems to fail to consider such a solution.  There seems to be 
advantages to the rooftop gardens established in the major cities of first world countries, 
such as Singapore and Hong Kong, which have many rooftop Gardens.   
People in cities are drawn to green areas such as parks and botanical gardens.  As more 
cities develop, fewer green areas are available for citizens to escape to.  Rooftop gardens 
might help eliminate the complete loss of green areas in cities (Peck & Kuhn, 2003: 3). 
1.3 THE RATIONALE 
The quality of air and living conditions in major cities in South Africa are continually declining 
as the cities, including Johannesburg, Cape Town and Durban, grow relentlessly.  Together 
with undesirable air quality, other challenges are present in growing cities (Rode & Burdett, 
2011: 454).  This problem needs to be addressed.  The expansion of cities requires land for 
development and comes at the expense of the natural environment, which is often removed 
completely.  The primary impact continued development has, is the resultant decrease in 
plant density which in turn decreases the quantity of clean air being produced.   
1 
 
If plants are replaced by creating rooftop gardens, it might help solve air quality and 
environmental issues (Grové, 2012: Online). It is necessary to research the validity of rooftop 
gardens in South Africa and the effect that green rooftop systems may have on the 
environment and living standard of people by considering both the advantages and 
disadvantages. 
1.4 PROBLEM STATEMENT 
Rooftop gardens are not getting the recognition for the positive contribution of it to the 
environment, the citizens, the industry and the buildings as such in South Africa.  This is due 
to a lack of knowledge and innovation.      
1.5 HYPOTHESES 
 
 Green rooftop systems is a new concept in South Africa and underdeveloped.  
 South Africa, and specifically Johannesburg, will benefit from the development of 
green rooftop systems, despite water shortage problems.   
 There is a demand for green rooftop systems in South Africa and the developments 
thereof will be feasible. 
 Green rooftop systems will contribute to the conservation indigenous plant species. 
 
1.6 THEORETICAL FRAMEWORK AND OBJECTIVE 
Air quality is decreasing as air pollution increases.  Global warming is a reality and the 
human population is expanding.  As a developing country, South Africa has not yet faced 
severe problems associated with its population; however, the South African population is 
increasing and the quality of living conditions seems to worsen (Momberg & Grant, 2008: 
Online).  It is not only poor air quality, but also the lack of natural elements and ineffective 
buildings that add to undesirable living conditions.  
There is a significant difference between flora and climates of South Africa compared 
globally. Therefore, rooftop gardens may require a different approach in South Africa than in 
other countries.  In South Africa, certain materials might or might not be available.  South 
Africa might have certain skills or a lack thereof.  Green rooftop systems might be a new 
concept for South Africans and a lack of knowledge goes with it.  It is necessary to 
determine the outcome of green rooftop systems in South Africa.  The future of the planet is 
the main objective and South Africa might contribute to sustaining nature and desirable 
conditions to live in. 
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Green rooftop systems might have a specific effect in cities of South Africa (Van Niekerk, 
Greenstone & Hickman, 2011: 5). 
Developers are at the forefront of developing cities.  Building regulations are used to 
regulate and implement a certain standard of development.  If both the developer and 
building regulations incorporate rooftop systems with new developments, it might give the 
implementation of green rooftop systems a boost (Kazmierczak & Carter, 2010: 3).    
The aim of this study is to determine how familiar or unfamiliar green rooftop systems are 
amongst the professionals in the construction industry as well as the citizens in South Africa 
and why.  Thus determining the level of knowledge in the construction industry, the reason of 
the level of knowledge and how to increase the level of knowledge in order to increase the 
development of green rooftop systems in South Africa.  Another objective is to determine if 
there is a demand for green rooftop systems and what advantages and disadvantages 
provided by the presence of green rooftop systems will have an impact on cities in South 
Africa.  An additional aim to the research is to determine the approach that needs to be 
taken in South Africa when constructing a green rooftop system.  
1.7 RESEARCH METHODOLOGY 
The research methodology was as follows: 
1.7.1 Literary review:  Journals, books, articles, internet and observations were used to 
gather sufficient information regarding rooftop gardens.   
 
1.7.2 Empirical study: Data were collected via questionnaires and field notes. 
 
1.8 CHAPTER OUTLAY 
The chapter outlay is as follows: 
CHAPTER 2:  INTRODUCTION TO GREEN ROOFTOP SYSTEMS 
This chapter introduces green rooftop systems and includes the history of green rooftops 
and types of green rooftop systems as well as a comparison of the types of green rooftop 
systems.   
 
 
 
3 
 
CHAPTER 3:  THE EFFECT OF GREEN ROOFTOPS IN CITIES 
Green rooftops in cities have various effects; advantages, disadvantages and changes in the 
city‟s behaviour.  The aim of this chapter is to determine all the possible effects of green 
rooftop systems in cities.   
CHAPTER 4:  CONSTRUCTING GREEN ROOFTOPS 
The aim of this chapter is to determine how to construct a green rooftop system and whether 
South Africa has the materials available that is needed to construct green rooftop systems. 
CHAPTER 5: PLANTS SUITABLE FOR GREEN ROOFS IN SOUTH AFRICA 
Plants that are indigenous to South Africa and that have the specific characteristics needed 
to survive on rooftops are listed.   
CHAPTER 6:  RESEARCH DESIGN AND METHODOLOGY 
Chapter 6 reviews the research design and methodology used to gather data for this study. 
CHAPTER 7:  FIELD NOTES – ROOFS IN JOHANNESBURG 
A field notes to analyse existing green rooftop systems in Johannesburg was conducted and 
is reported on in this chapter. 
CHAPTER 8:  EMPIRICAL STUDY IN GREEN ROOFTOP SYSTEMS IN SOUTH AFRICA 
This chapter provides an analysis of the empirical data.  Respondents‟ opinions are 
interpreted in order to determine the perspectives of South African citizens regarding green 
rooftop systems and to test the literature review.       
CHAPTER 9:  CONCLUSION AND RECOMMENDATIONS 
In this chapter conclusions are being drawn regarding the findings of the literary and 
empirical study.  From the conclusions, recommendations are given. 
Chapter 2 presents an introduction to green rooftop systems. 
 
 
 
 
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CHAPTER 2: INTRODUCTION TO GREEN ROOFTOP GARDENS 
2.1 INTRODUCTION 
Green rooftops have been part of construction for thousands of years.  The history of green 
rooftops will be discussed in this chapter as well as three different types of green rooftop 
systems and the elements that form part of a green rooftop system.   
2.2 THE HISTORY OF GREEN ROOFTOP GARDENS 
The human population is growing rapidly on a global basis.  Along with this rapid growth, 
cities are expanding and becoming urbanized.  More than 50% of the world‟s population 
lives in cities.  This rapid urbanization is putting pressure on sewage, fresh water supplies, 
the air quality, and living environment.  Carbon emissions are increasing and it is putting 
more pressure on ecosystems (Rode & Burdett, 2011: 454).   According to Petkova, Jack, 
Volavka-Close and Kinney (2013: Online), Africa currently has the fastest growing population 
in the world.  It is projected that the population of Africa will be more than double in 2050 
than it is in 2010.  Petkova et al. (2013: Online) predict that nearly 60% of Africa‟s population 
may soon be living in cities, compared to less than 40% in 2011.  According to Min, 
Fangying, Jiawei, Meixuan and He (2011: 922) a series of urban environmental problems 
have occurred in high-density urban environments. The problems include lack of open 
space, deterioration of the ecological environment, traffic jams, and population overload. 
A green rooftop is a planting system that allows for permanent and sustained living plants 
and covers a significant part of the roof of a building.  Green roofs may provide a wide range 
of economic, environmental and social benefits (Green Roofs, 2006: 1). 
Green (vegetated) roofs have been standard construction practice for thousands of years in 
different countries. It is thus not a new phenomenon (Peck & Kuhn, 2003: 2).  Peck and 
Kuhn (2003: 2) further state that the first known historical references to manmade gardens 
above ground were the ziggurats stone pyramidal stepped towers of ancient Mesopotamia, 
built from the fourth millennium until around 600 B.C.  In the thirteenth century France 
planted gardens on top of the Benedictine abbey.  Centuries ago, the Norwegians developed 
sod (plant and soil layers) roofs specifically for thermal insulation purposes.  Norway and the 
United States use sod homes as protection against extremely cold weather.  According to 
Magill, Midden, Groninger and Therrell (2011: 2), Canada has Viking and French examples 
of sod roofs which are found in Newfoundland and Nova Scotia.  During the middle ages and 
the Renaissance, the rich owned roof gardens as did the Benedictine monks.  Between 1933 
and 1936, five roof gardens were constructed on top of the seventh floor of the Rockefeller 
5 
 
Centre in New York City.  This was designed for enjoyment purposes for the tenants.  
Tenants pay higher costs for the luxury of having a garden view (Wark, C.G. & Wark, W. W., 
2003: Online). 
According to Peck and Kuhn (2003: 3), green roofs were considered part of domestic and 
functional architecture up until the mid-twentieth century.  Peck and Kuhn (2003: 3) further 
state that in the 1960‟s, concerns started growing regarding the degraded quality of urban 
spaces and green spaces that are rapidly declining.  This is when renewed interest was 
taken in green roofs in Northern Europe.  Breuning (2014: Online) states that modern green 
roof technology was initiated in the early seventies in Germany.  Germany started doing 
research and studies regarding drainage, root-repelling agents, membranes, plant suitability, 
and lightweight growing media.  Green roof systems were marketed and developed on a 
large scale.  In Germany, green rooftops started expanding rapidly in the 1980‟s.  The 
annual growth rate for green rooftops is 15-20%.  It ballooned from 1 to 10 million square 
metres of green rooftops by 1996.  This growth was stimulated mostly by municipal grants, 
state legislation, and incentives of between 35-40 Deutsch Mark per square meter of green 
rooftops.  Other countries including the USA, Denmark and Singapore have adopted similar 
support (Ansel & Appl, 2009: Online). According to Kaluvakolanu (2006: Online) green roof 
systems are becoming increasingly popular in the USA; however, green rooftop systems are 
not as common as in Europe, where cities, including Basel in Switzerland, incorporate green 
rooftops into the building regulations (Kazmierczak & Carter, 2010: 3).  Stuttgart‟s 
regulations require that all new industrial, flat-roofed buildings must have a green rooftop 
(Peck & Kuhn, 2003: 3).  
According to Peck and Kuhn (2003: 3), Vienna provides funds for new green rooftops at the 
planning stage, installation thereof and for maintenance three years post installation of green 
rooftop systems.  There may currently be over 75 European municipalities that provide 
requirements for the installation of green rooftops.  Botes (2013: Online) states that green 
roofs have become more popular in South Africa in the last nine years although it is still a 
new concept to the majority of the population. 
Castello (2011: 321) explains the concept of 'urban brownfields' as vacant space in cities 
that was previously used, but currently has no function.  The 'brownfields' are associated 
with post-industrial landscapes.  Castello (2011: 321) proposes that the vacant land to be 
used the fullest potential in order to promote a sustainable city.  Greening 'brownfields' may 
bring ecological benefits and in addition cleaning up the environment. 
 
6 
 
According to McConnachie, Shackleton and McGregor (2008: Online) developing countries 
lack efficient research regarding urban green space.  Fikret oglu Huseynov (2011: 534) 
acknowledges the importance of green spaces; as such green spaces serve as a place of 
identity, memory and belonging.  
2.3 GREEN ROOFTOP SYSTEMS 
According to Carpenter (2014: 4) a green rooftop is a vegetated landscape that is built up 
from various layers that are installed on top of a roofing system.  The green rooftop system 
may either consist of „loose laid‟ sheets or modular containers.  According to Peck and Kuhn 
(2003: 4) a green rooftop system could easily be confused with a traditional roof garden.  A 
traditional roof garden consists mainly of freestanding containers and planters that have 
been placed on an easy accessible roof, balcony or deck.  A contemporary green rooftop 
system consists of the following: 
 The vegetation, selected for a particular application, 
 A planting/growing medium, non-soil based planting medium, 
 A filter cloth, containing the roots and the growing medium, for water to penetrate it, 
 A drainage layer, 
 Waterproofing, including a root repellent to protect the membrane from root damage, 
 The roof structure, with insulation below or above (Biello, 2014: Online). 
2.3.1 Vegetation 
The limitations for the vegetation suitable for rooftops are geographical location, climate, 
structural design, availability of maintenance, and the depth of the planting medium.  Plants 
thriving in shallow planting medium seem ideal for rooftops.  According to C.G. Wark and 
W.W. Wark (2003: Online) a succulent ground cover (sedum) has become popular to use on 
green rooftops in North America.  Hearty wildflowers and grasses with shallow roots are 
commonly used on rooftops (Wark, C.G. & Wark, W. W., 2003: Online). 
According to GreenGrid (2014: Online) the plants that should be considered for an extensive 
green rooftop system includes deciduous, semi-evergreen, and evergreen „base‟ species 
with „accent‟ species.  The base mix is composed of five to eight different species of Sedum 
with one or two accent species.  An intensive green rooftop system may include a variety of 
native groundcovers, perennials, grasses, shrubs and/or even trees.  
Greenstone, Burring, Hickman and Nichols (2011: Online) state that the ideal vegetative 
layer to be applied to a green roof need to have the following characteristics:  
7 
 
 Drought resistant, 
 heat tolerant, 
 low growing, 
 self-seeding, 
 wind resistant, 
 and survive in extreme growing conditions. 
When selecting the plants, it is important to ensure that the plants have been acclimatised to 
withstand the conditions as mentioned by Greenstone et al. (2011: Online). 
2.3.2 Planting medium 
Planting medium is a mix of minerals, which is synthetically produced, expanded clay.  
According to Mississippi State University (2014: Online) Planting media is easily confused 
with soil.  The clay is considerably less dense than natural minerals and soil and is therefore 
lighter.  Expanded clay is more absorbent than natural soil.  A form of synthetically 
produced, expanded clay is called perlite, which is found in planting mix (not planting soil) at 
nurseries.  According to C.G Wark and W.W. Wark (2003: Online) there is a large number of 
planting medium recipes commercially available.  The densities of these mixes range from 
400kg per cubic metre to 900kg per cubic metre.  The planting medium may absorb 20-
200% of its weight.   
According to Skinner (2014: Online) planting media for green rooftop systems need to have 
the following characteristics: 
 Provide a stable structure for the anchorage of the plants‟ root systems, 
 be as lightweight as possible to prevent excess loading, 
 water permeable, 
 retain water, 
 resist rot, 
 provide nutrients, 
 possess chemical, physical, and biological characteristics necessary for supporting 
and sustaining vegetation. 
2.3.3 Containment 
With a modular system, the substrate, drainage and plants are contained within a lightweight 
high-density polyethylene module.  The dimensions of the modules may vary.  These 
modules are interlocked and form continuous roof coverage. In non-modular systems, the 
8 
 
planting medium is applied on top of the entire roof surface.  The green roof system is 
contained by the parapet walls of the roof or by a plastic or metal barrier (Velazquez, 2003: 
Online). 
2.3.4 Drain layer 
According to American Wick Drain (2014: Online), drainage is essential for managing the 
water content in the growing medium.  Excess water may cause roots to rot and too little 
water may result in poor vegetation growth. 
Green Roof Solutions (2014: Online) states that the most critical role of the drainage layer is 
to provide adequate flow of water to a point where it goes off the roof.  The flow of water is 
needed during and after a rain event.  The design of a drainage layer allows for some of the 
stormwater to be retained.  The design ensures that stormwater may be used by the plants 
for a longer time without oversaturation of the vegetation. 
Miller (2015: Online) concludes that the drainage system needs to maintain optimum 
growing conditions for the vegetation and manage heavy rainfall without sustaining damage 
due to erosion or ponding of water.   
2.3.5 Protective layer 
According to Conservation Technology (2008: Online) a protective layer, known as the root 
barrier, is needed if the waterproofing membrane is not resistant to root penetration.  The 
membrane of the roof needs protection, firstly, against damage when installing the green 
rooftop system, and against root penetration and fertilizers (Miller, 2015: Online).  Not all 
green roof systems require a protective layer.  The protective layer may be a sheet of rigid 
insulation, slab of lightweight concrete, copper foil, thick plastic sheet, or even a combination 
of the above.  The selection depends on the design of the green rooftop system (Wark, C.G. 
& Wark, W. W., 2003: Online). 
2.3.6 Insulation 
According to Greenroofs (2014: Online), insulation is an optional layer in a green roof 
system.  Insulation helps regulate the temperature of the building.  The design of the green 
roof system will influence the placement of the insulation, which may be placed under or 
over the roof deck, or over the waterproofing membrane. 
 
 
9 
 
2.3.7 Waterproofing 
According to the SANS 10400 Building Regulations (2008: 85), roofs must be able to resist 
penetration of water to the extent that water penetrating the roof will not run down the inside 
face of the walls onto the floor, or damp patches on the ceiling or floor. 
2.3.8 Irrigation 
There are different kinds of irrigation methods that may be used on rooftops.  The passive 
irrigation method is when rainwater is being stored in the drain layer.  The rainwater 
eventually wicks back up through the planting medium and excess water drains off.  
Polypropylene fiber mat is a type of water storage medium that may be put directly below the 
planting medium and acts as a sponge.  Another type of irrigation system includes small 
reservoirs in the drain mat.  Expanded clay fills the drain mat up to the bottom of the planting 
medium.  When sedums and drought-tolerant plants are used, irrigation is rarely necessary 
(Wark, C.G. & Wark, W. W., 2003: Online).  According to Carpenter (2013: 26), rainfall is 
generally not efficient to support a green rooftop throughout the year.  It is important to 
establish whether the rainwater or another source may be harvested from another area on 
the site, and stored to supply the irrigation system of the green rooftop.  This may minimize 
or eliminate the use of potable water for irrigation. 
Distinctive Design Group (2014: Online) offers two main types of irrigation systems in 
Gauteng.  The sprinkler system and drip irrigation system.  The sprinkler system may be set 
on a timer, which saves water and effort.  The drip irrigation system allows water to drip to 
the root of a plant using a network of pipes, drippers, valves and tubes.  Pressurised water 
or an electric pump is used to send water to the base of a plant using narrow tubes.  
According to Distinctive Design Group (2014: Online) water and fertilizer are saved by using 
the drip irrigation system.     
Some of these elements may be combined and need not be individual units.  For example, a 
filter layer may be used as a water storage mat.  The combination of elements could reduce 
the cost and weight of the rooftop system (Wark, C.G. & Wark, W. W., 2003: Online). 
2.4 TYPES OF ROOFTOP SYSTEMS 
There are three basic types of green rooftop systems: 
 Extensive 
 Semi-intensive 
 Intensive (National Roofing Contractors Association (NRCA), 2007: 27). 
10 
 
The three types of green rooftop systems are mainly differentiated by the depth of the 
growing medium (Peck & Kuhn, 2003: 4). 
2.4.1 Extensive green rooftops 
Extensive green rooftops are known as low-profile or low performance green systems.  It is 
designed for hydrological and thermal performance while it has minimum weight.  It may or 
may not be aesthetically pleasing (Carpenter, 2013: 4). 
Extensive green rooftops are typically not easily accessible and are characterized by the 
following: 
 It is shallow and lightweight, which means that the supporting structure required, may 
be less strong than the supporting structure for semi-intensive or intensive green 
rooftop systems, 
 it has a low capital cost, 
 the plant diversity is low, and  
 maintenance required is minimal (Grové, 2012: Online); 
 the roof frame may consist of either concrete, wood or steel; and 
 the plant mix may consist of sedums, moss and perennials (Vegetal Innovation & 
Development (VID), 2013: 12). 
The planting medium consists of a mixture of gravel, crushed brick, sand, peat, Light 
Expanded Clay Aggregate (LECA), organic matter, and soil.  The depth of the planting 
medium varies from 5cm to 15cm.  The weight of the planting medium between 72.6-
169.4kg/m² when fully saturated.  Some rooftops have an extreme desert-like microclimate.  
This together with the shallow planting medium allows for low hardy plants like succulents to 
survive.  The plants that seem to survive the shallow planting medium and desert-like 
microclimate are dryland, alpine and indigenous plants.  These plants need to be fertilized 
and watered only until they are established.  After that, maintenance consists of yearly 
checkups for invasive species, membrane inspection and safety (Peck & Kuhn, 2003: 4). 
Extensive green rooftops use a narrow range of species and are limited to low-growing 
grasses, mosses, herbs, and draught-tolerant succulents like sedum.  The latter is a plant 
variety that can tolerate extreme conditions.  These types of plants are comfortable growing 
in the shallow planting medium as well as steeper slopes.  The slopes can be steeper than 9 
degrees (NRCA, 2007: 30). 
11 
 
Figure 2.1 illustrates a section through an extensive rooftop system. 
 
Figure 2.1: A section through an extensive rooftop system. 
(NRCA, 2007: 30) 
Figure 2.1 illustrates eleven potential layers of an extensive green rooftop system.  The 
eleven layers consists of engineered soil 5-15cm deep with low plantings, filter fabric, 
reservoir layer (optional), moisture-retention layer, aeration layer, thermal insulation, 
drainage layer, root barrier, protection course, green roof waterproofing membrane and 
structural deck, prime as required.  Figure 2.1 defines the extensive green rooftop system 
thoroughly and may be used as a guideline in South Africa for constructing extensive green 
rooftop systems. 
 
 
12 
 
Figure 2.2 is a photo of an extensive rooftop system. 
 
Figure 2.2: An example of an extensive rooftop system. 
(Peck & Kuhn, 2003: 2) 
Figure 2.2 illustrates an example of an extensive green rooftop built on a roof with a slope.  
Access is not needed to the roof.  The plants survive by themselves.  In South Africa, this 
method may be applied as well in order to do as little damage as possible to the vegetation 
and to contribute to sustaining the natural environment. 
2.4.2 Semi-intensive green rooftops 
Semi-intensive rooftops may be either easily accessible or not easily accessible.  A semi-
intensive green rooftop system may accommodate more plant species than the extensive 
green rooftops.  Plants like small shrubs, grasses and herbs may form part of the semi-
intensive green rooftop.  The slope of the roof structure is, however, limited to a lower slope.  
The slopes may be 9 degrees or less.  The depth of the planting medium may vary from 15-
25cm.  The saturated weights for this system may vary from 169.4-290kg/m².  The 
landscaping for the semi-intensive green rooftop system requires less regular maintenance 
than the extensive rooftop system.   
13 
 
The plant diversity is, however, still quite limited due to the shallow planting medium.  The 
semi-intensive green rooftop system may require irrigation and a reservoir layer (NRCA, 
2007: 31). 
Figure 2.3 illustrates a section through a semi-intensive rooftop system. 
Figure 2.3: A section through a semi-intensive rooftop system. 
(NRCA, 2007: 31) 
Figure 2.3 illustrates eleven potential layers of an extensive green rooftop system.  The 
eleven layers consists of engineered soil 15-25cm deep with medium height plantings, filter 
fabric, reservoir layer (optional), moisture-retention layer, aeration layer, thermal insulation, 
drainage layer, root barrier, protection course, green roof waterproofing membrane and 
structural deck, prime as required.  Figure 2.3 defines the semi-intensive green rooftop 
system thoroughly and may be used as a guideline in South Africa for constructing semi-
intensive green rooftop systems. 
 
14 
 
Figure 2.4 is a photo of a semi-intensive rooftop system. 
 
 
 
 
 
 
 
 
Figure 2.4: An example of a semi-intensive rooftop system. 
(Zinco, 2001: Online) 
Figure 2.4 shows that a semi-intensive green rooftop system may have a variety of different 
types of shrubs and it may be designed to be aesthetically pleasing.  The semi-intensive 
green rooftop system, as shown in figure 2.4, does not need a large area to be attractive and 
practical.  Figure 2.4 is an excellent example of the potential of a semi-intensive green 
rooftop system and South African developers may use it as inspiration and guideline for 
future developments. 
2.4.3 Intensive green rooftops 
Intensive green rooftop systems are known as a high-profile green rooftop system, or 
generally as a rooftop garden (Wark, C.G. & Wark, W. W., 2003: Online).  Intensive green 
rooftops are typically easily accessible and are characterized by the following as compared 
to the previous two categories: 
 It has deeper soil and thus weighs more per square metre, 
 it has higher capital costs, 
 the plant diversity is higher, 
 it requires more maintenance (Grové, 2012: Online). 
The growing medium usually consists of soil based mixtures.  The depth of intensive green 
rooftops may vary from 20-60cm deep.   
15 
 
The saturated weight seems to be between 290-967.7kg/m².  Trees and shrubs may be 
included in the green rooftop because of the increased soil depth.  This means that the plant 
selection may be more diverse and may include shrubs and trees.  This allows for a more 
complex ecosystem.  Maintenance, however, is more demanding.  The plants need to be 
watered regularly.  A specialized irrigation system is often specified.  A structural engineer 
may need to be consulted as well as a horticultural specialist.  It is recommended that the 
installer is experienced (Peck & Kuhn, 2003: 5). 
The wide variety of plants that are accommodated by the intensive green rooftop system 
may include shrubs and trees.  The slope of the intensive green rooftop system is limited to 
1.2 degrees or less.  The Intensive green rooftop systems typically require an irrigation 
system and a heavy root barrier. A reservoir layer will be needed for these systems.  Due to 
the quantity of water that comes from the irrigation and weather conditions, an efficient 
drainage layer is required (NRSC, 2007: 32). 
Figure 2.5 illustrates a section through an intensive green rooftop system. 
 
Figure 2.5: A section through an intensive green rooftop system. 
(NRSC, 2007: 32). 
16 
 
Figure 2.5 illustrates eleven potential layers of an extensive green rooftop system.  The 
eleven layers consists of engineered soil 20-60cm deep with medium high plantings that 
may include trees, filter fabric, reservoir layer (optional), moisture-retention layer, aeration 
layer, thermal insulation, drainage layer, root barrier, protection course, green roof 
waterproofing membrane and structural deck, prime as required.  Figure 2.5 defines the 
intensive green rooftop system thoroughly and may be used as a guideline in South Africa 
for constructing intensive green rooftop systems. 
Figure 2.6 is a photo of an intensive rooftop system. 
 
Figure 2.6: An example of an intensive green rooftop system. 
(NRSC, 2007: 32) 
Figure 2.6 illustrates that an intensive green rooftop system may have a wide variety of 
plants, which may include trees. The rooftop is easy accessible.  It may be a recreational 
area where people may relax and enjoy the fresh air.  Figure 2.6 is an example of the 
potential of an extensive green rooftop system in a densely built urban area.  Cities in South 
Africa, for example Johannesburg, may use this example to see what the potential of such a 
green rooftop system may be and to improve on the green areas in the cities. 
Factors like location, budget, structural integrity, client needs, and the availability of material 
and plants contribute to the specific green rooftop.  Each rooftop will thus be different.  The 
green rooftop system may even be a combination of the intensive and extensive rooftop 
system (Peck & Kuhn, 2003: 5).  
 
17 
 
2.4.4 Modular rooftop system 
In some cases, the entire green rooftop system is contained in special gardening trays that 
cover most of the roof or the entire roof.  In a non-modular system, the planting medium is a 
continuous layer over the entire roof and is contained by the border of the roof, which may 
be a parapet wall (Wark, C.G. & Wark, W. W., 2003: Online). 
According to Van Niekerk et al. (2011: 24), a modular green rooftop system has the following 
characteristics set out in Table 2.1. 
Table 2.1: Modular characteristics 
 MODULAR CHARACTERISTICS 
Weight Modules may be installed on any existing roof surface that is in a good 
condition and with sufficient weight load capacity.  Modules may even be 
installed on corrugated roofs with a pitch up to 15 degrees. 
Installation Installing a modular green rooftop system may be quick, because the 
modules may be pre-planted off site.  The installation of a modular system 
may be done by an amateur as it is a user-friendly technique.  
Costs A modular system may be slightly more expensive than an extensive green 
rooftop system due to the cost of the modules. 
Repair and The modules may be moved easily without disturbing the plants and 
maintenance growing medium. 
Alterations Modules may be added and installed in sections.  Future add-ons and 
and additions alterations are thus always an option. 
Plants The modules may constrain root growth, which may cause some plants to 
struggle. 
 
(Van Niekerk et al., 2011: 24) 
Table 2.1 summarizes the characteristics of a modular system.  Modules may be installed on 
any existing roof surface that is in a good condition and with sufficient weight load capacity.  
Modules may even be installed on corrugated roofs with a pitch up to 15 degrees. Installing 
a modular green rooftop system may be quick, because the modules may be pre-planted off 
site.   
18 
 
The installation of a modular system can be done by an amateur as it is a user-friendly 
technique.  A modular system may be more expensive than an extensive green rooftop 
system due to the cost of the modules. The modules seem to allow movement without 
disturbing the plants and growing medium.  Modules may be added and installed in sections.  
Future add-ons and alterations are an option. The modules may constrain root growth, which 
may cause some plants to struggle.  The modular system seems to be easier to install on 
existing roofs than other green rooftop systems.  South Africans may apply the 
characteristics, advantages and disadvantages of the modular system to determine whether 
the system may work on a rooftop. 
Table 2.2 gives the comparison of the extensive, semi-intensive and intensive green rooftop 
systems 
Table 2.2: Comparison of the main types of green rooftop systems 
CRITERIA EXTENSIVE GREEN SEMI-INTENSIVE INTENSIVE GREEN 
ROOFTOP GREEN ROOFTOP ROOFTOP 
Vegetation Sedums, moss, Perennials, small Shrubs, trees, lawn 
perennials shrubs, lawn 
Plant diversity Low plant diversity Medium plant High plant diversity 
diversity 
Planting Medium 5-15cm deep 15-25cm deep 20-60cm deep 
Weight 72.6-169.4kg/m² 169.4-290kg/m² 290-967.7kg/m² 
Irrigation No Yes Yes 
Structural Frame Wood, steel, Concrete Concrete 
concrete 
Roof pitch Up to 30 degrees Up to 9 degrees 1.2 degrees or less 
Maintenance 
   
Roof Cost R RRR RRRR 
Accessibility Often inaccessible Limited Highly accessible 
 
 (Peck & Kuhn, 2003: 5; VID, 2013: 12)  
Table 2.2 is a comprehensive comparison of three types of green rooftop systems, namely 
the extensive green rooftop system, semi-intensive green rooftop system, and the intensive 
green rooftop system.  Different criteria are compared.   
19 
 
The criteria includes vegetation, the plant diversity, the depth of the planting medium, the 
weight per square meter, the need for irrigation, the structural frame needed, the roof pitch, 
the maintenance required, the average cost, and the accessibility required.   
The extensive green rooftop system has sedums, moss, and perennials as part of the 
vegetation.  The plant diversity is low.  The planting medium is on average 5-15cm deep.  
The extensive green rooftop system weighs on average between 72.6 and 169.4kg per 
square metre.  No irrigation is required.  The structural frame may be of wood, steel or 
concrete.  The roof pitch may be up to 30 degrees.  The extensive green rooftop system 
requires the least maintenance and it costs the least.  Accessibility is not a requirement.  
The semi-intensive green rooftop system has perennials, small shrubs, and lawn as part of 
the vegetation, which means that it has a medium plant diversity.  The planting medium is on 
average 15-25cm deep with an average weight of between 169.4 – 290kg per square metre.  
Irrigation is required.  The structural frame need to be of concrete and the roof pitch may not 
exceed 9 degrees.  The semi-intensive system requires more maintenance than the 
extensive system.  The cost of the semi-intensive system is between the costs of the 
extensive and intensive system.  Access is only needed for the maintenance crew.  If the 
space will be used as a recreational space, then access is required for the public.   
The intensive green rooftop system has lawn, trees and shrubs as part of the vegetation.  It 
has thus the highest plant diversity and the planting medium is the deepest, 20-60cm deep.  
The intensive rooftop system is the heaviest, 290-967.7kg per square meter.  Irrigation is 
required.  A concrete roof structure is required.  The roof pitch may not exceed 1.2 degrees.  
Compared to the other two rooftop systems the intensive system requires the most 
maintenance and it costs the most.  The main reason for an intensive rooftop system is for 
recreational purposes and accessibility is thus a priority.    
2.5 CONCLUSION 
Green rooftop systems are not a new phenomenon.  It has been in use for thousands of 
years for domestic and functional purposes.  In the 1960‟s, concerns started growing 
regarding the degraded quality and lack of green vegetated spaces in urban areas.  Northern 
Europe started doing research and developing commercial green rooftop systems.   
A green rooftop system consists of different layers.  These layers include the following: 
vegetation, planting/growing medium, filter layer, drain layer, protective layer, waterproofing, 
insulation, irrigation and roof structure.  
20 
 
There are three main types of rooftop systems: Extensive, semi-intensive and intensive 
systems.  These systems are differentiated by the depth of the planting medium and the 
amount of maintenance needed.   
Extensive green rooftop systems have a shallow planting medium; it is the lightest and 
cheapest green rooftop system and requires minimal maintenance.  The system is 
lightweight and thus might not require additional reinforcement.  The extensive system is 
suitable for large areas.  Irrigation is often not required.  Less technical expertise is required.  
The extensive rooftop systems may be suitable for retrofit projects.  Authorities may include 
the extensive system as a requirement for building approval.  The extensive system presents 
naturally and the vegetation may be left to grow spontaneously.  The extensive green rooftop 
system is less energy efficient than the other systems.  The vegetation is limited, access is 
limited and to some, the garden may be visually unattractive.     
A semi-intensive green rooftop system has a slightly deeper substrate, is more expensive 
and requires more maintenance than the extensive green rooftop system.  
Intensive green rooftop systems are known as roof gardens.  It has a deep planting medium 
which may accommodate a wide variety of plants.  An intensive green rooftop system is an 
expensive green rooftop system and requires intensive maintenance.  The intensive green 
rooftop system has more energy efficiency and stormwater retention capabilities compared 
to the other systems.  The insulation properties of the intensive green rooftop system are 
better than those of the extensive and semi-intensive green rooftop systems.  The intensive 
system may simulate a wildlife garden.  The diversity of vegetation and habitats are greater.  
The intensive system is usually attractive visually.  The system requires irrigation which 
might prove to be a problem in countries with periodic drought, such as South Africa.  The 
intensive green rooftop system has the greatest weight loading on the roof.  The system has 
the highest maintenance and capital cost compared to the extensive and semi-intensive 
systems.  This system might be more complex and thus requires more expertise.    
This comprehensive comparison might contribute to the decision making of what green 
rooftop system to install.  Each development is unique and each developer has a criteria.  By 
knowing the advantages, disadvantages, and criteria of each green rooftop system, it might 
contribute to making the right choice.   
The advantages, disadvantages and effects that green rooftops in a city might bring are 
important to consider, as this effects all the citizens of the involved city.  The potential effects 
will be discussed in the next chapter.  
21 
 
CHAPTER 3: THE EFFECT OF GREEN ROOFTOPS IN CITIES 
3.1 INTRODUCTION 
It is important to investigate the potential effects of green rooftop systems.  This may 
influence the validity of green rooftop systems in South Africa.   
According to Song (2011: 144), cities are unable to meet the functional needs of the 
expanding population due to the rural population that migrates to the urban cities.  The daily 
discharge of wastewater, waste gas, waste, and noise are far more than the self-purification 
capacity of the natural environment can bear.  
Song (2011: 144) states that as the population increases, the demand for food increase in 
such a way that the available agricultural land cannot sustain the population. 
3.2 ENERGY SAVINGS 
The green rooftop system acts as insulation.  In summer, the green plantings on the roof 
shades the building from solar radiation.  Through the process of evapotranspiration, the 
green rooftop system may reduce or eliminate heat gain.  Evapotranspiration thus helps to 
cool the surrounding area.  Due to the cooler surroundings, the building requires less energy 
to cool the building (Biello, 2014: Online).  According to Carpenter (2014: 9) the green 
rooftop system reduces the heat transfer through the roof and ambient temperature on the 
roof surface. 
In winter, the growing medium provides an additional layer of insulation.  This decreases the 
amount of energy needed to heat the building.  The extent of the energy cost savings may 
differ from building to building.  Impacting factors of the amount of energy savings include 
the size of the building, the building‟s location, the depth of the growing medium and the type 
of plants (Peck & Kuhn, 2003: 6).    
According to Peck and Kuhn (2003: 6) when the outside temperature is -20º C, 30cm of the 
growing medium will not experience temperature drops below 0º C.  However, the reduced 
need for air conditioning in summer is greater than the value added to the insulation in  
winter. 
According to Carpenter (2014: 8) research results vary in how much difference in 
temperature and amount of energy savings there are between buildings with green rooftop 
systems and building with conventional roofs.  The variety in the research results is because 
the amount of energy saved is dependent on the following: 
22 
 
 The percentage of the entire roof of the building that is covered by a green rooftop 
system. 
 The thickness of the insulation. 
 The height of the building. 
 The number of storeys in the building.  The floor directly below the green rooftop 
receives the most benefit. 
 The roof to wall ration. 
 The general climate of the area and the microclimate of the building. 
 The efficiency of the HVAC system. 
Due to the variety of variables, when the roof is being designed, all the factors that contribute 
to energy saving need to be taken into account in order to maximize the energy saving.  
According to Carpenter (2014: 9) the best results may be achieved in buildings with fewer 
than four storeys, a higher percentage of green roof coverage, deeper planting medium, and 
vegetation with large leaves. 
According to the European Federation of Green Roof Associations (EFB) (1999: Online) a 
green roof does not only act as insulation.  The combination of the plant processes, which 
include photosynthesis and evapotranspiration as well as the soil processes, evapo-
transmission reduces the amount of solar energy that is being absorbed.  The temperature 
beneath the roof is thus cooler due to the insulation properties, plant processes, and soil 
processes of a green rooftop system.  
Research done by Nottingham Trent University cited in EFB (1999: Online) has concluded 
the following: 
In summer, when the mean temperature is 18.4 ºC, the temperature beneath the membrane 
of the conventional roof is 32ºC and the temperature beneath a green rooftop system is 17 
ºC.  In winter, when the mean temperature is 0 ºC, the temperature beneath the 
conventional roof is 0.2 ºC and the temperature beneath the green rooftop system is 4.7 ºC 
(EFB, 1999: Online).  Research indicates that green rooftop systems have insulation and 
thermal properties.  It contributes to energy savings in summer as well as in winter.  The 
energy savings is, however, more in summer than in winter. 
Liu (2002: Online) compiled the following graph shown in figure 3.1 that indicates the 
fluctuation of daily temperatures of a conventional roof, ambient temperature, and a green 
roof. 
23 
 
 
Figure 3.1: Fluctuation of daily temperatures of a conventional roof, ambient temperature, 
and a green roof. 
(Liu, 2002: Online) 
In figure 3.1, the daily temperature fluctuations are shown for a conventional roof, the 
ambient temperature, and the temperature of a green roof.  The temperature of the green 
roof is lower than the ambient temperature in the months February, March, April, May, June, 
July, August, September and November.  In December and January, the temperature of the 
green roof is slightly warmer than the ambient temperature.  The temperature of the 
conventional roof is drastically higher than the ambient temperature in summer and cooler 
than the ambient temperature in winter.   
This shows that green rooftop systems contributes to energy saving due to less air 
conditioning needed in summer and less heating needed in winter compared to conventional 
roofs. 
3.3 LIFE EXTENSION OF THE ROOF MEMBRANE 
According to Grové (2012: Online) and Miller (2015: Online) the green rooftop system 
protects the roofing membrane from extreme temperature fluctuations.  The green rooftop 
system protects the roofing membrane from the negative impact of ultraviolet radiation and 
damage due to pedestrian traffic.   
24 
 
According to Greenroofs (2013: Online) green rooftop systems may increase the lifespan of 
a conventional roof by double the time, which prolongs the practical life of the roof to 20 
years.  Therefore, the replacement of the roof or rehabilitation may be delayed.  This 
contributes to the cost effectiveness of green rooftop systems. 
3.4 SOUND INSULATION 
Green rooftop systems may be designed to insulate sound (Grové, 2012: Online).  The 
growing medium may block the lower frequencies of sound and the plants may block the 
higher frequencies of sound.  According to Peck and Kuhn (2003: 7) tests show that 12cm of 
growing medium may reduce sound by up to 40 decibels.   
Van Renterghem and Botteldooren (2008: Online) conducted an experiment to determine 
the sound attenuation by a green roof measured in decibels.  Figure 3.2 illustrates the 
results of the sound attenuation of different substrate thickness and different sound 
frequencies.  
Figure 3.2 graphs the sound attenuation by a green roof, comparing different frequencies 
and different substrate thicknesses. 
Figure 3.2: Sound attenuation by green roof comparing different frequencies and different 
substrate thicknesses. 
(Van Renterghem & Botteldooren, 2008: Online) 
25 
 
In Figure 3.2, the sound attenuation of 10 different substrate thicknesses were tested and 
four different frequencies were compared.  The substrate thicknesses included 5mm up to 
50mm in 5mm stages.  The frequencies used were 125Hz, 250Hz, 500Hz and 1000Hz.  The 
higher the frequency, the better the sound attenuation.  This is due to the fact that low 
frequencies have large wavelengths that are not capable of entering the growing medium, 
and thus no or little attenuation occurs. The noise spectrum of traffic is at 1000Hz, and thus 
green rooftop systems contribute to shielding out some of the noise caused by traffic.  The 
figure illustrates that there is little difference between the sound attenuation of a 20mm thick 
substrate and a 50mm thick substrate.   
Connelly and Hodgson (2008: 4) explain that the larger the percentage of the roof is covered 
with a green rooftop system, the more sound attenuation will take place.  A tilted roof will 
improve the shielding against noise more than that of a flat roof, because there are more 
interaction with the sound waves and the substrate.  
3.5 FIRE RESISTANCE 
According to Peck and Kuhn (2003: 7) green rooftop systems may help to slow down the 
spread of fire to and from the building through the roof, especially where the growing 
medium is saturated.  However, if the plants are dry, it may present a fire hazard.  There 
should be „fire breaks‟ at regular intervals across the entire green rooftop system, along the 
perimeter and around all the penetrations.  The „fire breaks‟ need to consist of non-
combustible material; for example, concrete pavers or gravel.  The „fire breaks‟ need to be at 
least 60cm wide and located every 40m in all the directions.  Another option to consider is 
fire resistant plants such as sedums, because of their high water content.  Sprinkler irrigation 
may be connected to the fire alarm.  Single Ply Roofing Industry (SPRI) and Green Roofs for 
Healthy Cities (2010) developed an external fire design standard for vegetative roofs that 
has been approved by the American National Standard (ANSI).  SPRI and Green Roofs for 
Healthy Cities (2010: 7) state that vegetative green roofs have an excellent history of 
resisting fire damage.  Succulents, due to their water retention, is highly fire resistant.  
3.6 STORM WATER MANAGEMENT 
Green rooftop systems absorb, retain and detain stormwater.  Green rooftops represent a 
strategy that contributes to the control of the runoff rainwater in urban environments (Grové, 
2012: Online) and (Miller, 2015: Online).  Green rooftop systems intercept and retain 
rainwater from the early part of the storm.  Green rooftop systems limit the amount of run-off 
in larger rainstorms.  Water is stored in the planting medium; it is used by or stored in plants‟ 
26 
 
foliage, roots or stems, or it evaporates from the surface.  A green rooftop system with a 
water retention layer may have additional water storage capacity (Carpenter, 2014: 8). 
The extent of the stormwater control by the green rooftop system is dependent on the 
following factors (Carpenter, 2014: 8): 
 The depth of the planting medium. 
 The depth of the drainage layer. 
 The consistency of the planting medium. 
 The porosity of the planting medium. 
 The structure of the drainage system. 
 The slope of the site. 
 Plant species. 
 The type of drainage system. 
 The weather conditions of the region: the length, intensity, and frequency of rain 
events influence a green rooftop system‟s ability to retain water. 
3.7 URBAN HEAT ISLAND EFFECT 
Gardens on roofs could offset the local urban heat island effect and global warming (Biello, 
2014: Online). 
The Urban Heat Island Effect is the rise in the ambient temperature of an urban area due to 
hard surfaces in the urban environment such as roads, parking lots, conventional roofs, and 
buildings (Carpenter, 2014: 9).  
Middel, Chhetri and Quay (2015: 178) summarize the impact of the heat island effect as 
follows: increases air and surface temperature in the urban area; increases of outdoor water 
use; increase the demand of energy for cooling; lowers air quality; decreases thermal 
comfort; and increases morality related to heat stress as well as illnesses. 
Figure 3.3 illustrates the heat island effect. 
27 
 
 
Figure 3.3: The heat island effect 
(North Carolina State University, 2013b: Online) 
Figure 3.3 illustrates the four different temperatures in an urban area.  The four temperatures 
include the surface temperature during the day, the air temperature during the day, the 
surface temperature at night and the air temperature at night.   
These four different temperatures are compared for seven different areas within the urban 
area that includes rural, suburban, pond, warehouse/industrial, urban residential, downtown, 
and a park.  The surface temperature during the day is significantly higher than the air 
temperature during the day in the industrial area and downtown are due to the low albedo of 
the surfaces in these areas.  The more area covered by vegetation, the less the difference in 
the surface and air temperatures during the day.  The surface and air temperature at night 
are more or less the same.  However, both the air and surface temperatures are higher in 
the downtown and urban residential areas at night.   
According to the United States Environmental Protection Agency (U.S. EPA, 2014: Online), 
during a summer day, roofs and pavement surface temperature may be 27-50º C hotter than 
the temperature of the air.  Shaded and moist surfaces seem to have a temperature similar 
to the temperature of the air.  
28 
 
These surface temperatures contribute to the atmospheric urban heat islands.  According to 
Rosenburg (2014: Online) the air in an urban heat island may be as high as 11º C higher 
than rural areas that surround the city. 
The urban heat island effect may impact the environment in several ways:  
 The increased heat of cities increase the discomfort of the residents. 
 More energy is used to cool the temperature down. 
 It increases pollution (Rosenburg, 2014: Online) 
 Impaired water quality (U.S. EPA, 2013: Online) 
According to U.S. EPA (2013: Online), the increased temperatures and higher pollution 
levels associated with the heat island effect may effect human health and it may contribute 
to discomfort, respiratory difficulties, heat cramps, exhaustion, heat related mortality, and 
non-fatal heat stroke. 
U.S. EPA (2013: Online) states that the elevated summertime temperatures in cities 
increase energy consumption for cooling.  Electricity demand for cooling increases 1.5-2% 
for every 0.6º C increase in air temperature. 
The heat island effect increases smog (ground-level ozone) production due to the higher 
urban air temperatures.  Smog is created in the air by photochemical reactions of pollutants.  
These photochemical reactions may be intensified at higher temperatures.  As an example, 
in Los Angeles, smog increases by 5% for every 1º C that rise above 22º C (Akbari, 2005: 
2). 
U.S. EPA (2013: Online) found that the heated roofs and pavements may heat stormwater 
runoff.  Surfaces with a temperature of 38º C may elevate initial rainwater temperature from 
roughly 21º C to 35 º C.  This heated stormwater may drain into storm sewers and raise 
water temperature as it runs into streams, rivers, ponds, and lakes.  Aquatic life is directly 
affected by the temperature of the water.  Rapid temperature changes in aquatic ecosystems 
may be stressful or even fatal to aquatic life. 
According to Akbari (2005: 3) and Grové (2012: Online) there are two ways to mitigate the 
heat island effect.  A way is to use surfaces with high albedo characteristics.  The second 
option is to increase trees and vegetation in the cities.  Cities are already over developed 
and there is little space for planting vegetation.  Rooftops may be transformed into green 
rooftop systems.  
29 
 
Albedo is the measure of “how much light that hits a surface is reflected without being 
absorbed” (North Carolina State University, 2013a: Online).  Light colours reflect the most 
light and thus have a high albedo.  The darker the color, the more light is being absorbed 
and the lower the albedo.  Albedo is another name for reflectivity.   
The albedo of the surface determines how much sunlight will be absorbed.  More absorption 
of sunlight relates to a warmer surface temperature.  A surface that reflects most of the 
sunlight does not change temperature (North Carolina State University, 2013a: Online). 
Figure 3.4 illustrates albedo. 
 
Figure 3.4: High and Low Albedo 
(North Carolina State University, 2013a: Online) 
Figure 3.4 illustrates that light colored surfaces absorbs only 20% of the sunlight that hits the 
surface and it reflects 80% of the sunlight.  Dark surfaces absorb 90% of the sunlight that 
hits the surface and reflects 10%.   
According to North Carolina State University (2013a: Online) plants have a low albedo.  
Vegetated areas might reflect 3-20% of the sunlight and absorb the rest.  However, plants do 
not contribute to overall warmer temperatures.  The excess warmth is offset by evaporative 
cooling from transpiration.  
Green rooftop systems may mitigate the heat island effect.  According to Carpenter (2014: 
9), a study in Canada modeled the effect of green rooftop systems on the urban heat island.  
In the Canada study the conclusion was made that green rooftop systems may reduce local 
ambient temperature by 0.5º C - 2º C. 
30 
 
Figure 3.5 illustrates the direct and indirect benefits of cool surfaces. 
Strategies Processes Results 
Green Reduces Air Reduces Less Energy 
Direct 
Rooftop Conditioning demand at Consumed 
Systems use power plants 
Area sources Lower CO2, 
emit less NOx, and 
VOC levels 
Green Reduces Slows 
Rooftop Less Smog outdoor reaction 
Systems temperature rates 
Figure 3.5:  Green rooftop systems mitigating the heat island effect 
(Akbari, 2005: 5) 
The process how green rooftops may mitigate the heat island effect and the pollutions that 
goes with it is illustrated in Figure 3.5.  Green rooftop systems have direct and indirect 
benefits that oppose the heat island effect.  Green rooftops directly influence and reduce the 
air condition use in summer.  Green rooftops may reduce the outdoor temperature.   
The reduced use of air conditioning leads to a lower demand at the power supply and the 
result is less energy consumed.  The reduced outdoor temperature slows the photochemical 
reactions of pollutants and the result is thus less smog.  The reduced outdoor temperature 
leads to less emission of CO2, NOx, and VOC Levels which results in less smog.  
3.8 CREATION AND PRESERVATION OF HABITAT AND ECOLOGICAL BIODIVERSITY 
Green rooftop systems may contribute to enhancement of biodiversity and conservation.  
Green rooftop systems provide a habitat in areas where there is limited vegetation (Grové, 
2012: Online).  The green rooftop system may create new links between existing areas.   
Rare species may find refuge in green rooftop systems.  Green rooftop systems may even 
provide a link for migration of plants, birds and invertebrates (Carpenter, 2014: 9).  
According to Oberndorfer et al. (2007: 829) green roofs may contribute to local habitat 
31 
 
indirect 
 
conservation.  Studies have documented avian and invertebrate communities on a variety of 
green rooftop systems in several countries (Coffman, Davis, Brenneisen & Kadas in 
Oberndorfer et al., 2007: 829).  Green roofs are commonly inhabited by various insects, 
including ants, beetles, flies, bugs, spiders, bees, leafhoppers, and beetles (Coffman & 
Davis in Oberndorfer et al., 2007: 829).  Rare and uncommon spider and beetle species 
have been recorded on green rooftops (Brenneisen & Grant in Oberndorfer et al., 2007: 
829).  The richness of the spider and beetle species on green rooftops is positively 
correlated with the richness of the plant species as well as the topographic variability (Kadas 
in Oberndorfer et al., 2007: 829).  According to Baumann (2005: Online) green rooftops may 
be used by nesting birds. 
According to Van Niekerk et al. (2011: 10) green rooftop habitats may create green „stepping 
stones‟ between fragmented open spaces in urban areas.  This may encourage the 
movement of mobile species such as insects and birds.   
Figure 3.6 compares the amount of animals spotted on a green roof and blank roof between 
27 October 2010 and 2 February 2011. 
Figure 3.6 Comparison of animals spotted on a green roof and blank roof. 
(Van Niekerk et al., 2011: 10) 
Figure 3.6 compares the number of animals spotted on a green roof and a blank roof.  A 
total of 15 Sampling days were taken.  On average 221 insects were spotted on the green 
roof, with the highest catch on a single day being 365 insects.  In contrast, the average 
number of insects that were spotted on the blank roof was 2 insects with the highest catch 
on a single day being 11 insects.  A green rooftop thus contributes to a habitat for animals. 
32 
 
Figure 3.7 reflects the different species of animals that were spotted on the green rooftop 
system. 
 
Figure 3.7: The different animal species spotted on the green rooftop system 
(Van Niekerk et al. 2011: 10) 
Figure 3.7 indicates that 2344 animals were spotted on the green rooftop system.  This 
includes 1565 flies, 326 wasps, bees, and ants, 130 beetles, 133 butterflies, 126 thrips, 55 
spiders, 4 cockroaches, 3 ghekos, and 2 birds. 
According to Van Niekerk et al. (2011: 10) three different birds were spotted on a green 
rooftop in Durban, South Africa, namely the Paradise fly-catcher, White-Breasted Sunbird, 
and Black-eyed Bulbul. 
When designing for biodiversity, the plant species, building height and food sources need to 
be taken into consideration.  It is important to realize that plant species that have been 
selected primarily for stormwater management, aesthetic or human use may not be able to 
provide ecological diversity or a habitat.  It is thus important to decide on the objectives to be 
gained by the green rooftop system prior to its design (Carpenter, 2014: 8).   
3.9 AESTHETICS AND RECREATIONAL SPACE   
Cities that are undergoing rapid population growth and building development depend on 
space available.  Green rooftop systems may help increase the amenity, open space, food 
production, commercial and recreational space (Carpenter, 2014: 10).  
According to Grové (2012: Online) and Carpenter (2014: 10), it has been suggested that 
green spaces reduce stress, reduce patient recovery time, improve worker productivity, 
increase property values, decrease noise, and have even been linked to a reduction in 
crime. 
33 
 
Shuanggui, Jing and Shiyuan (2011: 253) point out that the era of green urban planning 
aims to replace the era of mechanical reproduction.  The mechanical era is seen as a 
depressing and boring age and the green era strives to bring more relaxed, and emotionally 
happy living conditions.   
According to Maas (2009: Online) people living in green environments feel and are healthier.  
More green space surrounding the living environment results in fewer visits to the doctor with 
complaints such as depression, COPD, dizziness, and diabetes.  People living in a green 
environment recover more quickly from stress.  Maas (2009: Online) states that “green 
space is more than just a luxury product, it actively promotes health”. Health records of 
350,000 people across the Netherlands were studied to determine the effect of green spaces 
on the annual rates of 24 physical diseases.  The study found that people living closer than 
1km from green spaces had lower rates of the diseases, particularly anxiety disorders and 
depression. 
Fjeld and Bonnevie (2002: Online) researched the effect of indoor plants on the well-being 
and health of workers.  The study found that the level of complaints is significantly lower 
among workers that had plants on their tables in the office.  The researchers argue that 
these results are due to a combination of the improved air quality in the office and the 
positive psychological effects of nature.  
An American researcher, Ulrich cited in Van Niekerk et al. (2011: 19), looked at the effect of 
a view from a window has on well-being and health.  Patients with a view of nature from their 
window had shorter post-operative hospital stays, required fewer injections of pain reducing 
drugs, and tended to have only minor post-surgical complications compared to the patients 
that looked out onto a brick wall. 
According to Carpenter (2014: 10) it may be difficult to create new gardens and parks on the 
ground as most space has already been taken up by built infrastructure.  It is, thus, important 
to use roofs for green spaces. 
3.10 URBAN AGRICULTURE 
According to Carpenter (2014: 10) urban agriculture contributes to ensuring food security, it 
may enhance community participation in the food system and it may even improve health.  
Green rooftop systems that produce food may become a community gathering place, which 
may provide food for local distribution, supplement a restaurant kitchen, or even be sold on a 
commercial scale. 
34 
 
According to Van Niekerk et al. (2011: 20) it is estimated that 15% of households in Durban 
do not earn enough money to pay for food.  Changes in climate may exacerbate the situation 
as agriculture is sensitive to climate changes.  This may result in increasing costs of food 
due to scarcity and imported food.  Rooftop agriculture may contribute to local food security.  
Agriculture on rooftop allows people to grow their own food.  
3.11 CREATING JOBS 
According to Green Roofs for Healthy Cities (2014a: Online) the growth of green roofs opens 
up new job opportunities for local people.  These job opportunities are related to 
manufacturing, design, plant growth, installation, and maintenance.  According to Lamb 
(2013: Online) the vegetable green rooftop garden concept in Cape Town revolves around 
exploiting job-creation opportunities.  This is done by recruiting homeless and unemployed 
people to build and maintain green roof structures, to grow and sell the vegetables to the 
deli‟s and restaurants downstairs. 
3.12 SUBSIDIZING GREEN ROOFTOP SYSTEMS 
According to Holzmüller (2009: Online) Düsseldorf in Germany has subsidized about 110 
projects from 2000 to 2009.  Düsseldorf has a population of 11 million people and is 
pursuing every available opportunity to boost the number of green roofs.  The efforts to 
create more green roofs in the city became the reason why Düsseldorf has been awarded 
the 2008 gold medal in the Europe-wide contest „Entente Florale‟. 
3.13 NATIONAL BUILDING REGULATIONS 
According to Kazmierczak and Carter (2010: Online) the city of Basel in Switzerland has the 
highest area of green roofs per capita in the world.  Since 2002, the building regulations of 
Basel were amended to include green roofs.  This goes to show that amending building 
regulations might make a difference in motivating the use of green rooftops.  Berry (2012: 
331) concludes that documents that serve as a communication instrument in die construction 
industry need to be updated regularly in order to improve the industry.  In this way, the entire 
construction industry will benefit from it. 
3.14 MONEY AS A MOTIVATOR 
Orando (2012: 26) concludes that money is an important motivator in human behavior.  If 
green rooftop systems prove to be economical and to increase revenue of developments, it 
may serve as a motivator to include green rooftop systems in future developments.  Given 
that developers aim to make a profit (Burger, 2013: 101), they may either choose to retain 
35 
 
some or all of the development or to sell the entire development.  Green rooftop systems 
may improve the profit margin. 
Tsung-Hsien and Yen-Lin (cited in Orando, 2013: 89) argue that the customer drives 
everything in the best companies.  This may be applicable to the demand in housing types.  
If the population living in the inner city would prefer to reside in a building with a green 
rooftop system and would be prepared to pay more for the option, the demand would 
increase.  When there is a demand for green rooftop systems on buildings, developers may 
use the opportunity to develop accordingly.  
3.15 AIR QUALITY 
Cities are challenged with several problems and air quality is one of them.  Air quality may 
be measured in order to regulate the air quality problem.  Worldwide, cities measure the 
quality of the ambient air on a daily basis and report on it.  Johannesburg is one of the cities 
that measure the air quality and is shown to be in a bad state.  It is important to be aware of 
the air quality of a city in order to know if it is systematically getting worse or better and if 
drastic measures should be taken to combat bad air quality.  This will benefit the decisions 
that needs to be taken for better air quality in the future or to sustain good air quality.  There 
are several particles present in the air of busy cities and it is important to establish whether 
there are toxic particles present and at what level.   
Rooftop gardens may be able to mitigate the polluted air.  According to Jedlinski (2014: 106) 
the US Environmental Protection Agency criteria for measuring the effectiveness of reducing 
the „carbon footprints‟ include the increase of the size of the green areas in a city.   
3.15.1 Air quality index 
According to AirNow (2014: Online) the air quality index (AQI) is an index for reporting air 
quality on a daily basis.  It is a measurement which tells you how clean or polluted the air is.  
The air quality index indicates what level of pollution is harmful to human health and to what 
degree.  The AQI runs on a scale form naught to five hundred (0-500).  An AQI value of 50 
or less represents healthy air quality.  The Environmental Protection Agency (EPA) 
considers readings below 100 as acceptable (AirNow, 2014: Online).  AQI values above 100 
are considered to be unhealthy for sensitive people.  As the AQI value gets higher, it 
becomes unhealthy for everyone.   
Table 3.1 categorizes the different levels of health concern and what each level means.   
 
36 
 
Table 3.1: AQI Categories     
Air Quality Index Levels of Health Concern Colours 
(AQI) Values 
When the AQI is in this ..air quality conditions ...as symbolized by this 
range: are: colour: 
0-50 Good Green 
51-100 Moderate Yellow 
101-150 Unhealthy for Sensitive 
Orange 
Groups 
151 to 200 Unhealthy Red 
201 to 300 Very Unhealthy Purple 
301 to 500 Hazardous Maroon 
 
 (AirNow, 2014: Online) 
There are six levels of health concern.  Good, moderate, unhealthy for sensitive groups, 
unhealthy, very unhealthy and hazardous.  „Good‟ implicates an AQI level reading of 0-50.  
The air pollution is minimal and poses little or no risk.  The air quality is considered to be 
satisfactory.  ‟Moderate‟ implicates an AQI level of 51-100.   
The air quality is considered to be acceptable; however, people who are unusually sensitive 
to ozone may be experiencing respiratory symptoms.  ‟Unhealthy‟ implicates an AQI value of 
101-150.  The general public might not be affected by the quality of the air, but sensitive 
citizens could be affected such as the elderly, children, and people with heart and lung 
problems.  ‟Unhealthy‟ implicates an AQI of 151-200.  At this level, everyone might start to 
experience adverse health effects.  ‟Very unhealthy‟ implicates an AQI reading of 201-300. 
When the AQI level is this high, it might result in a health alert where everyone may 
experience serious health effects.  ‟Hazardous‟ implicates and AQI level that exceeds 300.  
At this level, the entire population might be effected and health emergencies may occur.         
3.15.2 The air quality index of Johannesburg 
According to the Economist (2013: Online), the World Health Organisation measures the 
total mass of particles of 10-micron diameter or smaller per cubic meters on the AQI scale.  
This is called PM 10.  The PM 10 allows cross-country comparisons because it is widely 
used.   
Figure 3.8 reflects the 20 most polluted cities in the world with the biggest economies by 
using the AQI of PM 10. 
37 
 
 
Figure 3.8: The 20 most polluted cities in the world 
(Economist, 2013: Online) 
Figure 3.8 is a graph that illustrates the ranking of the 20 most polluted cities in the world by 
using the annual average AQI of PM 10.  The top 20 cities include the following: 
 Ludhiana in India has an AQI annual average of 251 PM 10 and according to the 
scale it is the most polluted city in the world. 
 Lanzhou in China has a reading of 150. 
 Mexicali in Mexico is at 138 
 Medan in Indonesia is at 112. 
 Anyang and Bussan in South Korea are both at 68. 
 Johannesburg is ranked the 7th most polluted city in the world and has a reading of 
66. 
 Rio de Janeiro in Brazil is 64. 
 Turin in Italy is at 47. 
 Seville and Zaragoza in Spain: 44 
 Paris in France: 38 
38 
 
 Bakersfield in the USA: 37 
 Montreal and Sarnia in Canada: 34 
 Moscow in Russia: 33 
 Dresden in Germany: 32 
 London in Britain: 30 
 Osaka in Japan: 28 
 Brisbane in Australia: 18  
Gondwana Environmental Solution (2007: 12) measured and recorded the pollutants present 
in the air of Johannesburg.  The measurements show that Johannesburg in South Africa falls 
under the cities that are polluted.   
Table 3.2 summarises the guidelines for the different pollutants present in the air of 
Johannesburg. 
Table 3.2: City of Johannesburg ambient air quality guideline 
Pollutant Average Period µg.    
Sulphur dioxide Annual 50 
Nitrogen dioxide Annual 40 
Nitrogen Oxide Annual 188 
Oxides of nitrogen Annual 284 
PM10 Annual 40 
Carbon monoxide 8 hour running average 10 000 
Lead Annual 0.5 
Ozone 8 hour running average 120 
PM2.5 24 hour 25 
Benzene Annual 10 
 
(Gondwana Environmental Solution (Pty) Ltd, 2007: 12)   
39 
 
Gondwana Environmental Solution (Pty) Ltd (2007: 34) measured the pollutants and 
intensity in the ambient air of Johannesburg and compared it with the guidelines.  It has 
been concluded that the PM10 is of the greatest concern.  The PM10 concentrations are at 
all times exceeding the air quality guidelines.  The situation is worse in the winter due to 
temperature inversions and calm winds, which promote the stagnations of the air pollutants.  
The rest of the criteria pollutants infrequently exceed the guideline. 
3.15.3 THE CAUSES OF THE POOR AIR QUALITY IN JOHANNESBURG 
Momberg and Grant (2008: Online) state that the air pollution levels in and around 
Johannesburg is worsening.  According to Gondwana Environmental Solution (Pty) Ltd 
(2007: 8-11), four causes of the poor air quality in Johannesburg include the following: 
3.15.3.1 Domestic Coal Burning 
Households in the City of Johannesburg use fuels such as paraffin, coal, and wood for space 
heating and cooking purposes.  The use of these fuels occurs especially in low-income 
areas that include Alexandra, Diepsloot, Orange Farm, and Soweto.  The rapid growth of 
informal settlements has resulted in a shortage of electricity and waste removal.  This is 
confirmed by Momberg and Grant (2008: Online). 
3.15.3.2 Vehicle emission 
According to British Columbia (2013: Online), vehicles emit the following: Nitrogen Oxides 
(NOx), Fine Particulate Matter (PM2.5), Volatile organic compounds (VOC's), Carbon 
Monoxide (CO), Sulphur Dioxide (SO2), Air Toxics, and Coolants (Momberg & Grant, 2008: 
Online) and (Enslin, [n.d.]: Online).  The City of Johannesburg (2012: 20) estimates that 
vehicles in Johannesburg emits 6.84 million tonnes of Carbon Dioxide (CO2) per year.  
Vehicles thus contributes to the greenhouse gasses and poor air quality in Johannesburg. 
3.15.3.3 Mining Operations 
Mining operations emits fugitive dust.  Particulate matter is the main pollutant.  Several 
activities add to the situation.  The activities include, drilling, blasting, truck on unpaved 
roads, loading and off-loading of material and storage piles and wind (Enslin, [n.d.]: Online). 
3.15.3.4 Industrial Activities  
The City of Johannesburg is home to large industries such as steel and iron processes, 
brickworks, and boiler operations.  Emissions from the industrial activities include SO2, NOx, 
and PM (Momberg & Grant, 2008: Online).    
40 
 
3.15.3.5 Waste Disposal and Incineration 
There are four operational landfills within the City of Johannesburg.  The four landfills include 
Robinson Deep landfill, Marie Louise Landfill, Goudkoppies landfill and Ennerdale landfill.  
The impact of poor management of landfills includes air pollution (City of Johannesburg, 
2009: Online).  
3.15.4 Cleaning the air with vegetation 
Vegetation offer the ability to remove air pollutants.  Subsequently, the environmental quality 
and human health improves (Connelly & Hodgson, 2008: 1).  Nowak, Crane and Stevens 
(2006: 121) estimated the percentage by which air quality may be improved due to air 
pollution removal by urban trees and shrubs.  It has been estimated that Portland in the US 
has a tree cover of 42% by Nowak et al. (2006: 121) and the percentage air quality 
improvement is estimated as follows: carbon monoxide (CO) improves by 0.003%,  nitrogen 
dioxide (NO2) may improve by 0.6%, ozone (03) may improve by 0.8%,  particles of 10-
micron diameter (PM10) may improve by 1% and sulphur dioxide    may improve by 0.7%.  
Nowak et al. (2006: 115) concludes that vegetation may help improve air quality for various 
different pollutants in cities.  The existing percentage of air quality improvement due to the 
removal of pollutants by urban trees and shrubs are modest.  However, it may be improved 
by increasing the urban vegetation cover.  
Johannesburg specifically will benefit from green rooftop systems because of the extensive 
pollution caused by domestic coal burning, mining operations and waste disposal and 
incineration as well as the general air pollutants which is vehicle emission and industrial 
activities. 
3.16 CONCLUSION 
Green rooftop systems contribute to a buildings‟ energy savings. The green rooftop system 
acts as insulation.  In summer, the green plantings on the roof shades the building from solar 
radiation.  In winter, the growing medium provides an additional layer of insulation.  
Green rooftop systems extend the life of the roof membrane. Green rooftop systems may 
increase the lifespan of a conventional roof by double the time, which prolongs the practical 
life of the roof to 20 years.  Green rooftop systems block sounds partially.  The growing 
medium may block the lower frequencies of sound and the plants may block the higher 
frequencies of sound.  Green rooftop systems may help slow down the spread of fire to and 
from the building through the roof, especially where the growing medium is saturated.  Green 
rooftops represent a strategy that contributes to the control of the runoff rainwater in urban 
41 
 
environments.  It is, thus, a viable tool for stormwater management.  Green rooftops help 
mitigate the urban heat island effect by lessening the dark, exposed concrete surfaces and 
by the transpiration process.  
Green rooftop systems provide a habitat in areas where there is little vegetation.  The green 
rooftop systems create new links between existing areas.  Additional habitats may be 
provided for rare or important species.  Green rooftop systems may help increase the 
amenity, open space and food production.  Green rooftop systems increase commercial and 
recreational space.  It has been suggested that green spaces reduce stress, reduce patient 
recovery time, improve worker productivity, increase property values, decrease noise, and 
have even been linked to a reduction in crime.  Rooftop spaces may even be used as urban 
agriculture space which contributes to help ensure food security. It enhances community 
participation in the food system and it may even improve health.  
Building regulations may be amended for the benefit of green rooftop systems and healthy 
cities. 
The air quality index (AQI) is an index for reporting air quality on a daily basis.  It is a 
measurement which tells how clean or polluted the air is.  Johannesburg is ranked the 7th 
most polluted city in the world and has a reading of 66 PM10.  Sulphur dioxide, Nitrogen 
dioxide, Nitrogen Oxide, Oxides of nitrogen, PM10, Carbon monoxide, Lead, Ozone, PM2.5, 
and Benzene are present in the ambient air of Johannesburg.  PM10 is of the greatest 
concern; however the rest of the pollutants do exceed the baseline at times.  
The causes of highly polluted air quality in Johannesburg are domestic coal burning, vehicle 
emission, mining operations, industrial activities, waste disposal and incineration.  
Vegetation may help improve air quality for various different pollutants in cities.  With a 42% 
tree cover in the city, the improvement of the air quality is more or less 1%.  However, the 
greater the area of plant and tree cover, the more air may be filtered by the vegetation.  
Before a green rooftop system is installed, the construction method and materials available 
in South Africa need to be considered as well as the factors that might be taken into account 
when constructing a green rooftop system.  Constructing a green rooftop system using 
South African products and methods will be presented in the next chapter.  
 
 
 
42 
 
CHAPTER 4: CONSTRUCTING GREEN ROOFTOPS 
4.1 INTRODUCTION 
There are certain factors that should be considered before designing and implementing a 
green rooftop system.  It is important to realize that each building, each site, each building 
owner, and each user differs.  Therefore, each green rooftop system will be different in order 
to fulfill the different needs and criteria (Peck & Kuhn, 2003: 10).  Factors like the access 
available, location, and climate, weight loading capacity, drainage system and professional 
team should all be taken into consideration when designing the green rooftop system.  The 
step-by-step installation procedure as well as the products available in South Africa will be 
discussed in this chapter. 
4.2 LOCATION AND CLIMATE 
The location of the site and the rooftop are important factors that contribute to the design of 
the green rooftop system.  Factors such as the height of the roof, wind exposure, the 
orientation of the roof to the sun, and the amount of shade due to surrounding buildings will 
have an impact on the design.  The microclimate and the general climate of the area should 
be taken in consideration when designing a green rooftop system.  The view to and from the 
rooftop will play a role in the design to obtain maximum effect (Peck & Kuhn, 2003: 10).  
According to Carpenter (2014: 26), the average wind speeds are greater at higher levels 
than ground level.  Wind may be strong around the edges of buildings.  Tall buildings may 
cause a strong down-draft wind.  When designing a green rooftop system, all wind forces 
need to be taken into consideration.  The structure and vegetation need to be able to 
withstand the wind forces these will be subjected to.  The temperature might be influenced 
by the wind shear and in turn will influence the plant selection.  
The light intensity tends to be greater at higher levels than at ground level.  The reason for 
the higher light intensity is the lack of vegetation and structures around to absorb the solar 
radiation.  In addition, the reflection from adjoining buildings and surfaces increases the 
radiation.  Conversely, some adjoining buildings may produce intense shading on the green 
rooftop (Carpenter, 2014: 26).   
According to Encyclopaedia Britannica (2015: Online), the temperature in urban 
environments tend to increase with elevation.  The increase in temperature is due to the 
increased thermal mass of built structures.  The likely temperature range of the rooftop is 
crucial in the planting selection. 
43 
 
Hepplewhite and Witkoppen Wildflower Nursery (2013: Online) explains that any garden has 
multiple micro-climates, even if it is only a few square metres in size.  The selection of plants 
for each specific area needs to correspond with each micro-climate.  The correct placement 
of the plant species will contribute to optimal plant growth rates, minimize watering and 
maintenance, and decrease plant death rates.  The design and selection of plants are 
therefore influenced by the location and climate.   
Table 4.1 lists the elements which need to be taken into consideration when identifying the 
micro-climate zones on a rooftop. 
Table 4.1: Elements to consider when identifying the micro-climate 
Element Description 
Regional Climate The general climate of the region needs to be taken into consideration 
when choosing plants for a green rooftop system.  For example, winter 
versus summer rainfall. 
Orientation Sloped roofs that face south or west are less exposed to direct sunlight 
and are therefore cooler and wetter. 
Sloped roofs that face north or east are more exposed to direct 
sunlight and are therefore warmer and drier.  
Wind Plants that are situated in exposed areas on the roof may experience 
higher wind influence.  Wind stresses plants more by increasing 
evaporation off their leaves, and by damaging foliage and branches.  
Shading Some areas on the roof may be subjected to shade due to adjacent 
buildings and/or structures.  The shaded areas might be permanently 
or periodically shaded. 
 
(Van Niekerk et al., 2011: 22) 
Table 4.1 summaries the micro-climate to consider when constructing a green rooftop 
system.  The elements that need to be considered include regional climate, orientation, wind 
and shading.  Regional climate is the general climate of the region and only certain plants 
are adapted to this climate.  The vegetation needs to be chosen accordingly.  The orientation 
involves the direction the rooftop garden is facing and whether the area gets mostly sunlight 
or shade.  The vegetation needs to be chosen accordingly.  The amount of wind that the roof 
is likely to get need to be considered as some species of vegetation are stressed by wind.  
Shading might be caused by neighboring buildings.  Some vegetation might not survive in 
44 
 
too much shade and other might thrive.  The micro-climate is thus an important factor when 
choosing the plant types for the roof.       
4.3 WEIGHT LOADING 
Before planning the green rooftop layout and vegetation, the weight loading capacity needs 
to be known (Biello, 2014: Online).  In case of a new building, the structural engineer is 
responsible for designing, advising on construction and determining the weight load capacity 
of the roof.  If it is an existing building, it is the structural engineers‟ responsibility to 
determine the structural integrity of the building and whether the building needs to be 
modified in order to support a green rooftop system.  It is possible to add structural elements 
like beams and columns to increase the weight loading capacity.  This needs to be designed 
by the structural engineer (Carpenter, 2014: 27). 
When designing the structure, the following loads need to be taken into consideration:  
 Dead load – this includes the final weight of the structure and everything that forms 
part of the roof: the planting medium, plants, roof structure. 
 Live load – this includes people and mobile equipment that will use the space. 
 Transient load – this is any moving, rolling or short-term loads and includes wind, 
seismic activity and water (Miller, 2015: Online).  
Table 4.2 indicates the proportional weight/m² for the different types of vegetation. 
Table 4.2: Weight loading as per vegetation type 
Green rooftop vegetation type Weight loading (kg/m²) 
Succulent and grasses 10.2 
Perennials and low shrubs up to 1.5m 10.2-20.4 
Turf 5.1 
Shrubs up to 3m 30.6 
Small trees up to 6m 40.8 
Medium trees up to 10m 61.2 
Large trees up to 15m 150 
 
 (Carpenter, 2014: 27) 
Table 4.2 summarizes the load per vegetation type.  Succulents and grasses may only have 
a weight load of 10.2kg/m².  As the plant species gets bigger, they require deeper growing 
medium.  Deeper planting medium means a heavier load/m².   
45 
 
Trees up to 15m high may result in a weight loading of 150kg/m².  When designing a green 
rooftop system, the structure needs to be able to support the desired vegetation‟s load.  The 
heavier the load, the more expensive the structure will be.  As the design, construction and 
development of a green rooftop system is a complex matter, professional consultants may 
be needed in order to complete the job successfully.     
4.4 CONSULTANTS 
The consultants that will form part of the professional team depend on the function of the 
green rooftop system, the size of the project, the project‟s location, and the experience of the 
project instigator (Peck & Kuhn, 2003: 10).  Technical knowledge and experience are 
essential in the built environment (Burger, 2013: 17).   
 Structural engineer: the structural engineer needs to determine the loading capacity 
of an existing roof structure and whether the structure is able to accommodate a 
green rooftop system.  If the roof structure is not strong enough to accommodate a 
green rooftop, it is the structural engineer‟s responsibility to design a retro-fit 
structure that will be able to hold the green rooftop system.  In the case of a new 
building, the structural engineer needs to take the load of the green rooftop system 
into account when designing the structure. 
 Civil engineer:  the civil engineer will be responsible for incorporating the green 
rooftop drainage system with the stormwater system of the building. 
 Architect:  an architect may be required to do the overall design of the building and 
incorporate the green rooftop in the design and specify the materials that should be 
used. 
 Landscape architect: the landscape architect will be responsible for designing the 
layout of the green rooftop system and to select the plants. 
 Mechanical engineer: the mechanical engineer will be required to calculate the 
cooling and heating implications of the green rooftop and to incorporate it in the 
HVAC design as necessary.    
 Specialist consultants may include a horticulturalist; and ecologist; biologist; a roofing 
consultant; an artist; and planner (Green Roofs for Healthy Cities, 2014b: Online).  
 Quantity Surveyor:  to determine the feasibility and cost of the project.  
 Project Manager: an effective project manager needs to have project management 
knowledge, interpersonal knowledge, technical knowledge and experience.   
According to Burger (2013: 17), a combination of these knowledge areas is needed in 
order to manage a project effectively and successfully.   
46 
 
4.5 DRAINAGE 
According to the Landscaping and Landscape Development Research Society (FLL) (2002: 
20), care needs to be taken from the beginning of the planning of a green rooftop system to 
ensure that proper drainage facilities are available from all areas, whether the area has been 
subjected to greening or not.  There are three different drainage systems that may be used 
to drain excess water off the roof.  
 Drainage within the vegetation area 
 Drainage outside the vegetation area 
 Separate drainage facilities for the green area and the area with no vegetation 
(FFL, 2002: 20). 
If the drainage facilities are located within the vegetated area, the green roof system needs 
to have at least one run-off facility and one emergency overflow, regardless of the size of the 
roof surface.  The run-off facility and emergency overflow needs to be designed according to 
SANS 10400 Building Regulations (2008).   
According to Carpenter (2014: 28), it is important to find out whether the site has a primary 
and/or secondary drainage system.  A primary roof drainage system may use simple 
waterspouts, box gutter for flat roofs, box drains built into the roof or eaves gutters for 
pitched roofs.  The primary drainage system may consist of these collector drains that are 
designed to flow only when it is partly full.   
Hydromax (2012: Online) explains primary and secondary drainage.  A primary drainage 
system is not designed to remove all the water that falls on the roof during heavy rain.  A 
green roof may thus require a separate secondary drainage system.  The secondary 
drainage system is known as the overflow relief system.  For nearly flat of flat roofs the 
primary drains are located at the lowest point of the roof.  The secondary or overflow drains 
are located at a higher point on the roof.  The overflow drains are designed to operate in the 
worst-case scenario when the primary drains are blocked and water is building up. The 
overflow drains remove the accumulated water and should be designed in such a way that 
the load of the accumulated water does not exceed the weight load capacity of the structure.   
According to Carpenter (2014: 28), for roofs with a low parapet wall, overflow drainage may 
be achieved by flowing over the edges.  To determine the necessity of an overflow relief, the 
expected rainfall intensity in conjunction with the existing performance of the primary 
drainage system needs to be considered. 
 
47 
 
Figure 4.1 illustrates the different types of drainage systems. 
 
Figure 4.1: A graphic illustration of different drainage systems 
(Carpenter, 2014: 28) 
Figure 4.1 illustrates that an eaves gutter is a channel that has been fixed to the edge of the 
roof to carry water to a designated downpipe.  Eaves gutters may fill up quickly in heavy 
rainfall.  Eaves gutters alone may not be sufficient as the drainage system for a green 
rooftop system.  It might get blocked and water may start building up.  This may cause plant 
species to drown.  However, if a gutter with a sufficient capacity is installed, it might be 
sufficient as the drainage system.  Therefore, when designing a green rooftop system, the 
expected rainfall of the district needs to be taken into account as well as the amount of water 
produced by the irrigation system.  A water spout is a hole through a parapet wall at various 
lowest points on the roof to discharge water from the edge of the roof.  In heavy rainfall, the 
water spouts may struggle to discharge water quickly enough and might get blocked.  A roof 
outlet is a hole through the roof that is situated at the lowest point on the roof.  A roof outlet 
is mainly for flat or nearly flat roofs.  An overflow drain is an example of a secondary drain.  It 
is holes that are higher up through the parapet wall.  The overflow drain discharges water 
once water has built up to the level of the overflow drain.   
Water removal from the roof is assisted by some degree of pitch or slope.  Roofs that look 
flat have a gentle fall to encourage movement of water into the drains.  This avoids ponding.  
Ponding is when water dams up on a roof for extended periods of time after rainfall.  
Deflection of the roof structure may be caused by recurring ponding.  This may cause the 
roof to become unstable and the drainage system may become inefficient.  A pitch of at least 
1.1º reduces the risk of ponding.  A steeper pitch will cause the roof to drain quickly (Wijte, 
2006: Online). 
 
 
48 
 
Figure 4.2 illustrates ponding. 
 
Figure 4.2: Ponding 
(Carpenter, 2014: 28) 
Figure 4.2 illustrates ponding on low points on the roof prevents water to flow down 
designated drainage systems.  Ponding may cause deflection in the roof structure.  To avoid 
ponding, the slope of the roof needs to be adjusted to direct water to a water outlet point, or 
a roof outlet needs to be installed at that point if possible.  
According to Carpenter (2014: 28), when assessing the site designing the drainage system, 
the following needs to be taken into consideration: 
 The amount of rainfall that lands directly on the roof. 
 The amount of water that drains from an adjacent roof or wall. 
 The duration of rainfall events. 
 The pitch of the roof determines the speed at which the rainfall collect in the drains. 
 The capacity of the drains.  This includes the dimensions and diameters of the 
gutters and downpipes. 
49 
 
4.6 ACCESS 
According to Peck and Kuhn (2003: 12) and Miller (2015: Online) access to the green 
rooftop is important for installation, ongoing maintenance and to bring up materials, soil and 
plants.  The extensive green rooftop systems need not have access for the public, as this 
type of system is not for recreational purposes.  The semi-intensive and intensive green 
rooftop systems, however, may need access for the public as it often serves the purpose of 
recreational space.  Safe access is needed (Garden and Home, 2015: 133).  
4.7 CONSTRUCTING THE DIFFERENT LAYERS WITH MATERIALS AVAILABLE IN 
SOUTH AFRICA 
After constructing a new building with a concrete roof slab or after an existing building‟s 
concrete roof has been tested and approved for a green rooftop system, the construction of 
the green rooftop system may commence.   
There are five layers that need to be installed in the construction of a green rooftop system.  
The layers consist of the following: 
Layer 1: Waterproofing 
Layer 2: Root Barrier 
Layer 3: Drainage layer 
Layer 4: Separation and additional root barrier layer 
Layer 5: Growing medium  
 
Each layer has specific materials and installation methods which is important to know. 
4.7.1 Layer 1: Waterproofing 
Derbigum is a waterproofing membrane that is manufactured in South Africa for South 
African Conditions (Derbigum Manufacturing, 2014: Online).   
The roof deck needs to be to falls or cross falls of 1:80 to the outlets where water drains out.  
The roof deck needs to be surface dry, clean and smooth, free of protrusions, voids and 
contaminants.  If all the requirements above are met, the surface is ready to be primed with 
a bituminous primer.  The internal corners should be filleted and the external corners 
rounded (Derbigum Manufacturing, 2014: Online). 
Generally, surfaces that receive a Derbigum modified-bitumen membrane need to be primed 
with a bitumen primer.   
50 
 
According to Derbigum Manufacturing (2014: Online) the specification for installing 
Derbigum for Horticultural purposes is as follows: “One layer Derbigum CG4H (horticultural) 
on one layer Derbigum CG3 waterproofing membrane, laid staggered with side laps of 
100mm and end laps of 150mm, sealed to bitumen primed surfaces by torch-fusion.”  
Figure 4.3 illustrates Derbigum on a roof.  
 
Figure 4.3: Derbigum waterproofing membrane  
(Perrins, 2013: Online) 
Figure 4.3 illustrates installed Derbigum on an existing roof.  The next step of the rooftop 
garden construction may proceed.   
4.7.2 Layer 2: Root Barrier 
An efficient and light root barrier is 250 micron (DPM) polythene sheeting.  According to the 
supplier, Polyfast (2010: Online), the black DBM polythene sheet has a high tear resistance, 
great tensile strength and it is BBA approved.  It is thus suitable as a resistant membrane.   
The 250 micron polythene sheeting is to be loose laid on top of the waterproofing membrane 
with 100mm laps and sealed with a pressure-sensitive tape (Derbigum Manufacturing, 2014: 
Online). 
51 
 
Figure 4.4 illustrates black 250 micron (DPM) polythene sheeting. 
Figure 4.4: Black 250 micron (DPM) polythene sheeting 
(Polyfast, 2010: Online) 
Figure 4.4 indicates the black 250 micron (DPM) polythene sheeting that needs to be used 
for step 2 in the construction of the green rooftop system.   
4.7.3 Layer 3: Drainage layer 
The Delta MS20P (perforated) high density polyethylene dimpled drainage layer is a product 
of the Waterproofing Centre.  According to Waterproofing Centre (2013: Online), Delta 
MS20P is perforated dimple sheeting with a high drainage capacity.  It is designed for 
horizontal use on roof slabs, under floor slabs and for roof landscaping. The porosity makes 
the dimpled sheeting pervious over the whole area which provides uniform drainage of 
water.  
Figure 4.5 illustrates Delta MS20P (perforated) polyethylene dimpled sheeting. 
Figure 4.5: Delta MS20P (perforated) polyethylene dimpled sheeting 
52 
 
(Waterproofing Centre, 2013: Online)  
Figure 4.5 indicates the Delta MS20P (perforated) polyethylene dimpled sheeting which 
needs to be used for step 3 in the construction of the green rooftop system.   
The dimple sheeting may be rolled out on the polythene sheeting.  The dimples should be 
facing the surface and the cups needs to be facing up. The sheeting may be cut with a 
blade.  To extend a sheet, two rows of dimples need to be overlapped (Waterproofing 
Centre, 2013: Online).  
4.7.4 Layer 4: Separation and additional root barrier layer 
Bidim is a nonwoven, continuous filament, needle punched, polyester geotextile.  Bidim is a 
product of Kaytech Engineered Fabrics, a South African company.  According to Van 
Niekerk et al. (2011: 26) the Bidim A2 is the best option for green rooftop systems.  Bidim A2 
has several favourable properties. Bidim A2 has a mass of 150g/m2, 1.6mm thick and has a 
penetration load of 1.8kN.  Bidim A2 has a porosity percentage of 93% (Kayteck, 2013: 
Online). 
To install Bidim, the sheet needs to be rolled on the desired surface.  The entire surface 
dedicated to the green rooftop system needs to be covered with the Bidim.  To ensure 
proper coverage, Bidim may be joined by one of the following methods (Kaytech, 2013: 
Online): 
 Sufficient overlapping.  Frictional resistance keep it in place. 
 Sewing with polyester thread. 
 Blanket stitching by sewing galvanized wire or polyester thread. 
 Stapling with wire or rods.  
Figure 4.6 illustrates Bidim and the four different ways to join Bidim sheets together. 
53 
 
Figure 4.6: The installation of Bidim and the four joining methods 
(Kayteck, 2013: Online) 
Figure 4.6 Illustrates Bidim and the four joining methods: 
1. Overlapping 
2. Sewing with polyester thread. 
3. Blanket stitching with polyester thread and galvanized wire. 
4. Stapling with wire or rods 
The joining method is dependent on the strength of the subgrade.  If the subgrade is strong 
enough, the overlapping method is sufficient (Geofabrics Australia, 2009: Online).    
4.7.5 Layer 5: Growing medium  
The growing medium should ideally be lightweight, well-drained, and be able to retain a high 
degree of water without becoming waterlogged (Miller, 2015: Online).  Planting media made 
up of materials such as perlite, expanded clay, vermiculite and volcanic rock are the best 
suited for green rooftop systems.  The best ratio for the mix should be 60-80% inorganic 
materials and 20-40% organic materials (Van Niekerk et al., 2011: 29). 
The potential inorganic media includes vermiculite, perlite, Berea red sand, dark building 
sand, decomposed granite, and crushed brick.  Van Niekerk et al. (2011: 29) did a study on 
the mentioned growing media and concluded as follows: 
 Vermiculite has a saturated weight of 178 grams per litre, which is known to be 
extremely light weight. The cost is reasonable and vermiculite is readily available.  
Unfortunately vermiculite might break down over a long period of time. 
54 
 
 Perlite has a saturated weight of 174 grams per litre, which is lighter than vermiculite.  
Perlite is the most expensive of inorganic material, but readily available.  Over a long 
period of time, perlite might break down. 
 Berea red sand has a saturated weight of 2 kilograms per litre, which is heavy if 
compared to vermiculite and perlite.  Availability is seldom a problem. 
 Dark building sand has a saturated weight of 2 kilograms per litre.  The weight is the 
same as the Berea Red Sand and is classified as heavy.  The cost is reasonable and 
the product is readily available. 
 Decomposed granite has a saturated weight of 2 kilograms per litre, which is the 
same as berea building sand and dark building sand.  Decomposed granite is readily 
available and affordable.  Macro- and micro- nutrients, which are both essential for 
plant growth are being released as granite decomposes.  
 Crushed brick has a saturated weight of 2 kilograms per litre.  When the relevant 
machinery is not available, crushing bricks are not probable.  
The potential organic media includes compost and potting mix.  The characteristics of 
the organic media are as follows (Van Niekerk et al., 2011: 29): 
 Compost has a saturated weight of per 760 grams per litre and is readily available at 
a low cost. 
 Potting mix has the same saturated weight than compost which is 760 grams per 
litre.  Potting mix is readily available with a low cost.  
According to Hickman (2013b: Online) the best growing medium mix for light weight roof 
systems in South Africa includes expanded perlite, expanded vermiculite and finely 
shredded, well-rotted bark.  The mix is light weight, affordable and has a sufficient water 
holding capacity. 
4.8 COMMUNICATION, NEGOTIATION AND PERSUASION OF IMPLEMENTATION 
Communication is seen as the starting point and foundation of activities in the construction 
industry (Zulch, 2012: 199).  Communication may thus be the key to start introducing green 
rooftop gardens into the construction and development community of South Africa.  
According to Clements and Gido (2012: 312) negotiation is the process of bargaining.  The 
aim of the bargaining is to reach an agreement with project stakeholders or accomplish 
tasks. 
55 
 
Zulch (2012: 87) states that negotiation as a skill may be used in various stages of the 
communication during a project, and may be useful in reaching agreements.  Thus, 
negotiation and persuasion might be needed to encourage green rooftop systems. 
Conferences may be considered as a communication tool.  A conference is defined as “an 
event, sometimes lasting a few days, at which there is a group of talks on a particular 
subject, or a meeting in which especially business matters are discussed formally” according 
to Cambridge Dictionaries (2015: Online).  Conferences may help inform the involved parties 
about the „how to‟ regarding green rooftop systems as well as the advantages and 
disadvantages.  The involved parties may include construction contractors, landscape 
architects, engineers, quantity surveyors, developers and the government.  If the problem is 
lack of knowledge, conferences might help solve the problem and help develop green 
rooftop systems as much as possible.  Competitions might help motivate and encourage 
cities, or individual parties to develop proper rooftop gardens.  Public buildings may be used 
as displays and may contribute to the persuasion to develop green rooftop systems. 
4.9 PUBLIC BUILDINGS AS AN EXAMPLE FOR GREEN ROOFTOP SYSTEMS 
In Vietnam, a kindergarten was built with a vegetable garden on the roof.  The aim of this 
design was to initiate a prototype for a sustainable school design, where children may learn 
how to grow food (Dezeen, 2014: Online).   
Figure 4.7 is a photo of the preschool in Vietnam named Farming Kindergarten. 
 
Figure 4.7: Farming Kindergarten, Vietnam 
(Dezeen, 2014: Online) 
56 
 
Figure 4.7 is a photo of a preschool in Vietnam featuring a vegetable garden on the roof and 
three protected courtyards with vegetation.  Public buildings like Farming Kindergarten may 
be an effective way to introduce the country of the potential of green roofs. 
4.10 CONCLUSION 
The location and climate need to be taken into consideration when designing the rooftop 
garden and when deciding what types of plant species will best adapt to the location and 
climate.  The regional climate, wind, solar radiation, temperature and shade seems to be 
factors to take into consideration.   
It is important to know what the weight load capacity is of the structure and how heavy each 
layer is that will be installed in order to make sure that the weight load capacity is not 
exceeded.  The dead weight, live weight and transient weight need to be taken into 
calculation. 
The professional team may consist of a structural engineer, civil engineer, architect, 
landscape architect, mechanical engineer, horticulturalist, ecologist, biologist, a roofing 
consultant, an artist, planner and/or quantity surveyor.  The number of different consultants 
that will be needed for the design and construct of the green rooftop system depends on the 
scope of the green rooftop garden. 
The roof needs to have a primary and secondary drainage system.  The primary drainage 
system is to drain water at the lowest points on the roof and the secondary drainage system 
is an overflow backup system for when the water starts to build up.  Access to the roof is 
important for installation, ongoing maintenance and to get the material on the roof.   
There are five layers that need to be constructed prior the vegetation layer.  Layer one is the 
waterproofing layer that consists of derbigum.  Layer two is the root barrier that is made out 
of 250 micron polythene sheeting.  Layer three is the internal drainage system, which 
consists of Delta MS20P (perforated) polyethylene dimpled sheeting.  Layer four is the 
separation and additional root barrier layer (the Bidim A2 geotextile) and the fifth layer is the 
planting medium, which should ideally be lightweight, well-drained, and be able to retain a 
high degree of water without becoming waterlogged.  The planting medium mix should be 
60-80% inorganic materials and 20-40% organic materials. 
As an example, public buildings that are built with a green rooftop system, may educate the 
population about the possibilities of green rooftop systems.  The sixth layer is plants.  An in-
depth study seems important, therefore in chapter 5 plant species are reviewed.  
57 
 
CHAPTER 5: PLANTS SUITABLE FOR GREEN ROOFS IN SOUTH AFRICA 
5.1 INTRODUCTION 
In order for plants to survive on rooftops, they may need to have certain characteristics.  
Plants need to be hardy; survive in windy conditions and full sun; and must be able to grow 
in shallow substrate.  Plants need to survive and thrive in the local general climate; for 
example, winter rainfall, summer rainfall, dry winters, temperatures below freezing point, 
humidity, heat and severe summers.  South Africa has a diverse climate and different plant 
species will be suitable for growing on rooftops in the different regions.  According to Breuste 
(2004: Online), the use of indigenous vegetation for urban landscaping is a problem and not 
considered a priority when planning and making decisions.  Indigenous vegetation needs to 
become an important aspect of urban biodiversity.  
5.2 THE TYPES OF SPECIES THAT ARE SUITABLE FOR GROWING ON ROOFTOPS IN 
SOUTH AFRICA 
The following plants seem to be appropriate for roofs in South Africa according to Stern and 
Mutshinyalo (2002: Online), Notten (2002: Online), Hankey (2009: Online), Ngalo (2010: 
Online), Jamieson (2002: Online), Van Jaarsveld (2005: Online), Turner (2001: Online), 
Malan and Notten (2005: Online), Kurzweil (2004: Online), Klopper (2007: Online), Williams, 
Raimondo, Crouch, Cunningham, Scott-Shaw, Lötter and Ngwenya (2008: Online), Foden 
and Potter (2014: Online), Snijman and Victor (2004: Online) and Mills (2013: Online). 
5.2.1 Cassinopsis Ilicifolia (Hochst.) 
According to Stern and Mutshinyalo (2002: Online,) the common name for Cassinopsis 
ilicifolia (Hochst.) is lemon thorn in English.  The lemon thorn does not have an aggressive 
root system and may be used as a pot plant.  The lemon thorn is an attractive plant due to 
the bright, glossy, green foliage, orange fruits and the drooping habit of the stems.  The plant 
grows naturally in montane forest, on forest margins, along streams and in wooded kloofs in 
riverine bush from the southern and eastern Cape to the Eastern Free State, KwaZulu-Natal, 
Gauteng and Mpumalanga.  The fruits are eaten by birds including starlings, barbets, 
pigeons, guineafowl, bulbuls, and francolins.  The plant tolerates drought and frost and 
grows in either shade or sun (Stern & Mutshinyalo, 2002: Online).  According to Petal Faire 
Nursery (2014: Online) the lemon thorn is a hardy, evergreen shrub which grow up to 3m 
high. 
Figure 5.1 is a photo of the lemon thorn shrub. 
58 
 
 
Figure 5.1: Lemon thorn shrub 
(Stern and Mutshinyalo, 2002: Online) 
5.2.2 Eucomis autumnalis (Mill.) Chitt 
According The Royal Horticultural Society (2015: Online), the common name for Eucomis 
autumnalis (Mill.) Chitt is autumn pineapple lily in English.  The Royal Horticultural Society 
(2015: Online) states that the pineapple flower is a deciduous, summer-growing bulb which 
is generally pest and disease free.  No pruning is required.  The stem of the bulb grow up to 
40cm and the overall height of the plant is up to 50-60cm high.  Notten (2002: Online) further 
states that the subspecies E. Clavata grows naturally in open grassland and marshes in 
KwaZulu-Natal, the Eastern Free State, Gauteng, North West Province, and Mpumalanga.  
The pineapple plant is not difficult to grow.  Once the plant is established, it does not require 
much attention.  The plant is comfortable in full sun or partly shaded areas.  The plant is 
dormant in die winter, but it will still tolerate winter irrigation and winter rainfall as long as the 
substrate is well drained.  The pineapple plant is frost hardy and may survive a winter 
minimum of -7 ºC. 
Figure 5.2 is a photo of the pineapple flower.  
 
Figure 5.2: Pineapple flower 
Notten (2002: Online) 
59 
 
5.2.3 Portulacaria afra (Jacq.) 
According to Hankey (2009: Online), the common name for Portulacaria afra (Jacq.) is 
porkbush in English.  It is generally known as the spekboom as well.  It is a popular 
succulent garden plant.  The porkbush is an attractive, evergreen succulent shrub or small 
tree that reach 1.5-2m in height in a garden situation.  It is a rich source of nectar for many 
insects.  The porkbush grows naturally in warm climates on rocky slopes in succulent karoo 
scrub, thicket, bushveld and dry river valleys in the eastern parts of South Africa from the 
Eastern Cape northwards into KwaZulu-Natal, Limpopo and Mpumalanga.  The porkbush is 
a versatile plant and may be planted in full sun or partly shaded areas.  The plant grows in 
dry areas as well as well-watered flower beds.  The bush tolerates frost to a moderate 
degree, especially when it is mature. 
According to The Spekboom Foundation (2015: Online) the porkbush is an excellent “carbon 
sponge”.  The porkbush has the ability to absorb free carbon from the atmosphere, which is 
used to produce plant tissue.  The porkbush is ten times more effective per hectare at 
carbon fixing than a rain forest.  Each hectare of porkbush could capture 4.2 tons of carbon 
annually.  
Mills (2013: Online) states that the spekboom grows primarily in the Eastern Cape and 
Western Cape.  The spekboom grows in desert-like climates like a cactus.  This means that 
the spekboom absorbs carbon dioxide at night.  Macleod (2008: Online) explains that the 
spekboom has enormous carbon-storing capabilities.  The spekboom has the capacity to 
offset harmful carbon emissions equivalent to a moist subtropical forest.  
Figure 5.3 is a photo of the porkbush.   
 
Figure 5.3: Porkbush 
60 
 
(Hankey, 2009: Online) 
5.2.4 Aloe maculata  
According to Ngalo (2010: Online) the common name for Aloe maculata is soap aloe in 
English.  This species grows naturally from the Cape Peninsula through the Western and 
Eastern Cape, Eastern Free State, KwaZulu-Natal and Mpumalanga.  The soap aloe prefers 
the milder coastal climates, yet is also found in the higher altitude of the Drakensberg.   
They occur in various habitats which include rocky areas, thicket and grasslands.  The 
flowers are a rich source of nectar and attract sunbirds. 
Figure 5.4 is a photo of the soap aloe. 
 
Figure 5.4: Soap aloe 
(Ngalo, 2010: Online) 
5.2.5 Aloe arborescens  
According to Hankey and Notten (2004: Online) the common name for Aloe arborescens is 
kranz aloe in English.  The kranz aloe occurs mainly over the eastern, summer rainfall areas 
of South Africa.  It has the third widest distribution of any aloe. The kranz aloe occurs from 
the Cape Peninsula along the eastern coast, KwaZulu-Natal, Mpumalanga and Limpopo.  
The kranz aloe grows in various habitats, which include exposed ridges on mountainous 
areas and dense bush.  The habitats stretch from sea level to mountain tops.  The kranz 
aloe is easy to grow.  The plant grows in full sun, well-drained substrate and tolerate 
moderate frost.  It will tolerate drought and does not need maintenance once established.  
 
 
 
61 
 
Figure 5.5 is a photo of the kranz aloe.  
 
Figure 5.5 Kranz Aloe 
(Hankey & Notten, 2004: Online) 
5.2.6 Asparagus densiflorus 
According to Jamieson (2002: Online) the common name for Asparagus densiflorus is 
asparagus fern in English.  Asparagus fern is a versatile perennial, evergreen plant that can 
be used as a container plant or ground cover.  The plant grows in full sun or light shade.  
The asparagus fern occurs in the coastal areas in KwaZulu-Natal and the southern part of 
the Eastern Cape.  The plants habitats include rocky areas, coastal dunes or woods.  It 
withstands temperatures of UP to -7 ºC and it is drought tolerant.  The plant grow up to 60cm 
high.  The asparagus fern has berries which attracts birds. 
Figure 5.6 is a photo of the asparagus fern. 
 
Figure 5.6: Asparagus fern 
(Jamieson, 2002: Online) 
62 
 
5.2.7 Aleollanthus parvifolius 
According to Van Jaarsveld (2005: Online), the common name for Aleollanthus parvifolius is 
klipsalie in Afrikaans.  The plant is a drought-tolerant succulent and it is suitable for dry 
bushveld and grassland gardens.  The plant occurs in the northern Eastern Cape to 
Mpumalanga Drakensberg and surrounding area as well as the Western Cape.  The klipsalie 
is resistant to light frost and it can re-sprout after a cold season.  It thrives in containers and 
rockeries. 
Figure 5.7 is a photo of the klipsalie. 
 
Figure 5.7: Klipsalie 
Van Jaarsveld (2005: Online) 
5.2.8 Agapanthus inapertus P.Beauv. 
According to Turner (2001: Online), the common name for Agapanthus inapertus is drooping 
agapanthus in English.  The drooping agapanthus occurs naturally in grassland, forest 
margins through northern KwaZulu-Natal, Mpumalanga, Gauteng and the Northern Province.  
The habitats of the plant include mountainous, rocky areas and it is common along the 
Drakensberg Escarpment.  The drooping agapanthus grow up to 1.5m high.  The plant 
requires little attention once it has been established.  The drooping agapanthus grows well in 
most soils as long as it is well drained.  It thrives in full sun and the plant is relatively pest 
free.  The plant is deciduous and it is ideal for summer rainfall, water-wise gardens.  It is 
dormant during winter and does not require watering in this period.  It could actually 
withstand irrigation during winter.  The drooping agapanthus withstands frost. 
 
63 
 
Figure 5.8 is a photo of the drooping agapanthus. 
 
Figure 5.8: Drooping agapanthus 
(Turner, 2001: Online) 
5.2.9 Crassula ovata 
According to Malan and Notten (2005: Online), the common name for the Crassula ovata is 
jade plant in English.  The plant is an evergreen shrub that grow up to 1-3m high.  The jade 
plant occurs in the Eastern Cape and KwaZulu-Natal on rocky hillsides.  The plant grows 
easily in loam soil as long as it is well drained.  It thrives in full sun or partly shaded areas.  
The plant is tolerant to drought, coastal conditions and wind.  It may be able to withstand 
temperatures as low as -1 ºC.  The plant grows well in pots. 
Figure 5.9 is a photo of the jade plant.  
 
Figure 5.9: Jade plant   
(Malan & Notten, 2005: Online) 
64 
 
5.2.10 Crassula Expansa 
According to Hickman (2013c: Online) the crassula expansa is a dwarf, mat-forming 
succulent.  The crassula expansa is drought resistant.  It is, however, susceptible to attack 
by the mealy bug.  They have shown to grow in shallow soils and to withstand extreme heat 
and drought.  The Crassula Expansa establish themselves easily.  The plant with its white 
flowers attract insects, in particular the honey bee.  The soil needs to be properly drained, 
otherwise the roots will rot. 
Figure 5.10 is a photo of the Crassula Expansa. 
 
Figure 5.10: Crassula Expansa 
(2013c: Online) 
5.2.11 Albuca Setosa 
According to Williams et al. (2008: Online), the common name for the albuca setosa is 
slymstok in Afrikaans.  It is wide spread in South Africa.  The provinces include the Eastern 
Cape, Free State, Gauteng, Kwa-Zulu Natal, Limpopo, Mpumalanga, Northern Cape, North 
West, and Western Cape.  It occurs in rocky slopes and flats.  According to the Hickman 
(2013a: Online) the plant is drought resistant.  The soil needs to be properly drained.   
Figure 5.11 is a photo of the slymstok. 
65 
 
 
Figure 5.11: Slymstok 
(Williams et al., 2008: Online) 
5.2.12 Bulbine narcissifolia 
According to Klopper (2007: Online), the common name for bulbine narcissifolia is snake 
flower in English.  The plant is hardy and does not require much attention.  The plant occurs 
from the far eastern regions of the Western Cape, Kwa-Zulu Natal, Free State, North West, 
Gauteng and Limpopo.  The plant is frost and drought tolerant.  The plant is fast growing and 
prefers full sun.  
Figure 5.12 is a photo of the snake flower.  
 
Figure 5.12: Snake flower 
(Klopper, 2007: Online) 
66 
 
5.2.13 Eulophia speciosa 
According to Kurzweil (2004: Online), to grow the eulophia speciosa is easy.  There are, 
however, certain rules that need to be strictly followed.  The plant requires full sun.  The 
eulophia speciosa occurs from the George-Knysna area through the Eastern Cape and 
northwards to Kwa-Zulu Natal, Mpumalanga and Limpopo. 
Figure 5.13 is a photo of the Eulophia speciosa. 
 
Figure 5.13: Eulophia Speciosa 
(Kurzweil, 2004: Online) 
5.2.14 Delosperma lineare 
According to Burgoyne (2014a: Online), the Delosperma occurs naturally in KwaZulu-Natal.  
Hickman (2013f: Online) states that the delosperma lineare responds well to irrigation, yet 
survives extended periods of drought.  The plant grows in shallow, fertile substrate.  The 
substrate needs to be well drained. 
Figure 5.14 is a photo of the Delosperma lineare. 
67 
 
 
Figure 5.14: Delosperma lineare 
(Hickman, 2013f: Online) 
5.2.15 Delosperma tradescantioides 
The Delosperma occurs naturally in KwaZulu-Natal, Mpumalanga, and Eastern Cape 
(Burgoyne, 2014b: Online).  According to Hickman (2013g: Online), the Delosperma 
tradescantioides has proven to grow on green rooftops in the Durban area.  The plant 
survives periods of drought and grows well in shallow substrate. 
Figure 5.15 is a photo of the Delosperma tradescantioides.  
 
Figure 3.15: Delosperma tradescantioides  
(Hickman, 2013g: Online) 
5.2.16 Gladiolus dalenii 
Ngalo (2011: Online) states that the common name for Gladiolus dalenii is african gladiolus 
in English.  The plant grows naturally in the summer rainfall regions of the Eastern Cape 
north of East Londen to southern KwaZulu-Natal, from the coast to the border of Lesotho.  
Sunbirds are attracted to the copious nectar. It needs to be planted in full sun, in well-
drained substrate.  According to Hickman (2013h: Online) the plant is not particularly drought 
68 
 
resistant; however, it is dormant in winter and requires less water then.  It needs to be 
planted in a substrate depth of at least 100mm. 
Figure 5.16 is a photo of the african gladiolus. 
 
 Figure 5.16: African Gladiolus 
(Ngalo, 2011: Online) 
5.2.17 Plectranthus Spicatus 
The Plectranthus spicatus occurs naturally in the Eastern Cape, KwaZulu-Natal, Limpopo 
and Mpumalanga (Foden & Potter, 2014c: Online).  According to Hickman (2013i: Online) 
the plant is drought resistant and has proven to grow on green rooftops in the Durban Area.  
The plant is one of the larval host plants used by the Gaudy Commodore Butterfly, which 
they readily attract.  The Plectranthus spicatus, however, tends to smother other plants due 
to its vigorous growth and caution should be taken in this regard.   
Figure 5.17 is a photo of the Plectranthus Spicatus.   
69 
 
 
Figure 5.17: Plectranthus Spicatus 
Hickman (2013i: Online) 
5.2.18 Cyrtanthus Sanguineus  
According to Snijman and Victor (2004: Online), the Cyrtanthus Sanguineus occurs naturally 
in the Eastern Cape and KwaZulu-Natal.  Hickman (2013e: Online) states that the 
Cyrtanthus Sanguineus is a medium-sized, clump-forming bulb.  The plant is drought 
resistant and grows where there is virtually no ground cover.  The Cyrtanthus Sanguineus, 
however, needs to be shaded by other vegetation.  The plant has proven to grow in rooftop 
gardens in the Durban area. 
Figure 5.18 is a photo of the Cyrtanthus Sanguineus. 
 
 Figure 5.18: Cyrtanthus Sanguineus 
(Hickman, 2013e: Online) 
 
70 
 
5.2.19 Kalanchoe thyrsiflora 
The Kalanchoe thyrisflora occurs naturally in the Free State, Gauteng, KwaZulu-Natal, 
Limpopo, Mpumalanga and North West (Foden & Potter, 2014b: Online).  Voigt (2005: 
Online) states that the common name for the Kalanchoe thyrisflora is meelplakkie in 
Afrikaans.  The Kalanchoe thyrsiflora is a succulent perennial and it does not require much 
attention in a sunny, dry garden. 
Figure 5.19 is a photo of the Kalanchoe thyrsiflora. 
 
Figure 5.19: Kalanchoe thyrsiflora 
(Voigt, 2005: Online) 
5.2.20 Cyanotis Speciosa 
According to Foden and Potter (2014a: Online) the Cyanotis Speciosa grows naturally in 
Eastern Cape, Free State, KwaZulu-Natal, Western Cape, Limpopo, Mpumalanga, Northern 
Cape and North West.  Hickman (2013d: Online) explains that the Cyanotis Speciosa is a 
low-growing, evergreen scrambling plant.  The plant is drought resistant and withstand wet 
conditions without rotting.  
 
 
 
71 
 
Figure 5.20 is a photo of the Cyanotis Speciosa.  
 
Figure 5.20: Cyanotis Speciosa  
(Hickman, 2013d: Online) 
The plants, lemon thorn, pineapple flower, porkbush, soap aloe, kranz aloe, klipsalie, 
asparagus fern, drooping agapanthus, Jade plant, crassula expansa, snake flower, slymstok, 
eulophia speciose, Delosperma lineare, Delosperma tradescantioides, african gladiolus, 
Plectranthus spicatus, Crytanthus Sanguineus, meelplakkie, Spekboom and Cyanotis 
Speciosa all possess the qualities to survive on roofs.  Some of the plants have already 
proven to survive on roofs in the Durban area. 
5.3 PLANTS SUITABLE FOR ROOFS IN JOHANNESBURG 
According to The Local Government Handbook (2014: Online), the Johannesburg 
Metropolitan is the largest city in South Africa.  Green rooftop systems in Johannesburg 
might improve the living conditions of citizens. 
Table 5.1 is a summary of the plants that might be suitable for green rooftops in the City of 
Johannesburg. 
 
 
 
 
 
 
72 
 
Table 5.1: Plants suitable for green rooftop systems in Johannesburg 
Scientific Name General Name Image of Plant 
Cassinopsis Ilicifolia Hochst. lemon thorn 
 
Eucomis autumnalis (Mill.) pineapple flower 
Chitt 
 
Portulacria afra Jacq. porkbush 
 
Aloe maculata soap aloe 
 
Aloe arborescens kranz aloe 
 
Aleollanthus parvifolius klipsalie 
 
Agapanthus inapertus drooping agapanthus 
P.Beauv. 
 
Albuca Setosa slymstok 
 
Bulbine narcissifolia snake flower 
 
Kalanchoe thyrsiflora meelplakkie 
 
 
Cyanotis Speciosa doll's powderpuff 
 
 
Table 5.1 summarizes eleven plant species that might grow and thrive on green rooftop 
systems in Gauteng.  The plants are lemon thorn, pineapple flower, porkbush, soap aloe, 
kranz aloe, klipsalie, drooping agapanthus, slymstok, snake flower, meelplakkie, and doll's 
powderpuff.  The reasons why these plants may be suitable for roofs in Gauteng is because 
they are indigenous to the area and have the characteristics required to survive conditions 
on roofs.  The table includes the scientific and general known name for each plant with a 
photo. 
 
73 
 
5.4 CONCLUSION 
Eleven species have been identified that might thrive on a green rooftop system in Gauteng.  
These species includes perennials, succulents and shrubs.  The plants include the lemon 
thorn, pineapple flower, porkbush, soap aloe, kranz aloe, klipsalie, drooping agapanthus, 
slymstok, snake flower, meelplakkie, and doll's powderpuff.  Some of the plant species have 
beautiful flowers.  Beautiful green spaces may be developed using the appropriate plant 
species.   
In Chapter 6, the detail of the research design and methodology used in the study is 
presented. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
74 
 
CHAPTER 6: RESEARCH DESIGN AND METHODOLOGY 
6.1 INTRODUCTION 
This chapter provides the detail of the research design and methodology used in the study.  
The research approach is explained by the research method.  The methodology discusses 
the data collection using a control group (Burger, 2013: 159).   
Green rooftop systems is a new concept to South Africa, and obstacles need to be 
overcome before development can take place.  The obstacles need to be determined in 
order to be able to be eliminated. 
Before the development of green rooftop systems may be encouraged, it is necessary to 
determine if there is a demand for it in South Africa; Is it feasible, what type of system would 
be the best for South Africa and what are the effects that green rooftop systems might have 
in South Africa? 
Entering an era where green rooftop systems may be an essential part of development, it 
seems important to determine the level of competence and knowledge of South Africans in 
the construction industry regarding green rooftop systems.  It is necessary to be determined 
and address the lack of skill and knowledge before developing green rooftop systems.   
An empirical study is important to test the literature study.  The following elements are tested 
with the empirical study: 
 the familiarity of green rooftop systems of professionals in the construction industry 
as well as citizens of Johannesburg; 
 the feasibility of green rooftop systems in South Africa; 
 the factors that encourage the development of green rooftop systems; 
 the benefits from green rooftop systems in the city of Johannesburg; 
 the possibility of a demand for green rooftop systems in South Africa; 
 how disadvantages of green rooftop systems would effect the future development 
thereof; 
 what methods would be effective to implement in order to increase green rooftop 
system developments;  
 what plants would be suitable for the South African weather to form part of green 
rooftop systems. 
 
 
75 
 
6.2 RESEARCH STRATEGY 
Research strategy is derived from the methodological paradigm that refers to qualitative and 
quantitative research (Burger, 2013: 162). Qualitative research is the study of systems by 
interacting with and observing the involved participating elements.  The emphasis is on the 
quality and depth of the information and not the scope or breadth of the information provided 
by quantitative research (Maree, 2007: 51).  Quantitative research is a process that is 
systematic and objective in the ways of using numerical data from only a selected subgroup 
of a population to generalise the findings to the population that is being studied (Maree, 
2007: 145).  The research includes both quantitative and qualitative method to determine the 
perspective of green rooftop systems in South Africa.  The qualitative research involved field 
notes.  Certain observations have been made and deductions have been derived at.  The 
quantitative research was done by means of questionnaires.  From the questionnaires, data 
were gathered, analysed and statistics compiled.  Therefore the qualitative and quantitative 
methods are applied to test the literature information empirically.           
6.3 METHODOLOGY 
The methods used to gather data include the use of books, internet websites, articles, 
research papers and scientific journals for the literature study.  The tools used to obtain the 
resources are the library and the internet.   
The empirical data were gathered by means of field notes and questionnaires.  
Questionnaires were sent out to the individuals working in the built environment to obtain 
expert opinions as well as to citizens of Johannesburg in order to obtain the view and 
perspective of the general population regarding green rooftop systems.   
6.3.1 Questionnaire survey 
The questionnaire group consists of quantity surveyors, architects, engineers, contractors 
and citizens of Johannesburg.  Quantity surveying is the main focus and therefore more 
quantity surveyors were approached than other professional members.  The questionnaires 
were sent out electronically via email in 2015.  The questionnaires received were analysed 
and transformed into statistics in order to do comparisons and draw conclusions.  The 
respondents who received questionnaire received a phone call after two weeks to inform 
them of the importance of their reply to the study.  The opinions and knowledge of the 
respondents, gathered by means of questionnaires, are used to determine the general skill 
set for the installation and construction of green rooftop systems in South Africa and how 
green rooftop systems may contribute to a healthier South Africa.  
76 
 
Several of the questions has a Likert scale from 1 – 5 in order to indicate to what degree the 
respondents agree or disagree with the specific question/statement.  The scale indicates the 
following: 
1 – strongly disagree 
2 – disagree 
3 – neutral 
4 – agree 
5 – strongly agree 
 
6.3.2 Field notes 
When observing a setting, field notes are created by the researcher to remember and record 
the features of the setting being observed.  Field notes are meant to be analysed by the 
researcher to produce meaning and an understanding of the situation or phenomenon being 
studied (Cohen & Crabtree, 2008: Online).  Field notes were taken and forms part of the 
research.  The data collected from the field notes are analysed.  The data are carefully 
scrutinised and organised in order to reveal patterns, do comparisons and draw conclusions.   
The field notes used in this project involved the investigation of existing green rooftop 
systems in Johannesburg and existing roofs in Johannesburg with the potential for green 
rooftop systems. 
6.4 CONCLUSION 
This study was undertaken using a systematic process of collecting and interpreting data in 
order to make deductions and conclusions of green rooftop systems in South Africa.  The 
research data was collected by quantitative and qualitative methods.  Field notes were taken 
as the qualitative method and questionnaires were sent out as the quantitative method to 
obtain expert opinions as well as to citizens of Johannesburg in order to obtain the view and 
perspective of the general population regarding green rooftop systems.  The data provide 
the information needed to be able to make deductions.  The field notes were taken form the 
observation of existing green rooftop systems in Johannesburg CBD area and existing roofs 
in Johannesburg with the potential for green rooftop systems. 
The research findings from the field notes are presented in chapter 7.  
77 
 
CHAPTER 7: FIELD NOTES - ROOFS IN JOHANNESBURG 
7.1 INTRODUCTION 
Rooftops in Johannesburg were investigated and analysed to find green rooftop systems 
and potential rooftops for green rooftop systems. 
7.2 ROOFS IN JOHANNESBURG CBD 
There is potential for green rooftop systems in Johannesburg CBD.  Figure 7.1 is a photo 
taken from a skyscraper in Johannesburg CBD, which indicates the roofs of the surrounding 
buildings. 
 
Figure 7.1: Roofs of buildings in Johannesburg CBD 
Figure 7.1 illustrates that there are multiple roofs in Johannesburg CBD with the potential for 
the development of green rooftop systems.  As the photo illustrates, there are no green 
rooftop systems visible, therefore it seems that there is no attention to the development of 
green rooftop systems in the Johannesburg CBD area from professionals in the built 
78 
 
environment to develop green rooftop systems.  Thus the deduction may be made that the 
benefits of green rooftop systems are ignored or unknown.  
7.3 GREEN ROOFTOP SYSTEMS IN JOHANNESBURG 
The only green rooftop systems found in Johannesburg are analysed.  Three rooftop 
systems in Sandton, a financial hub, form part of the field notes as well as a house in the 
suburbs.  The commercial buildings with the green rooftop systems in Sandton are: 
 DaVinci Hotel 
 The Michelanglo 
 Sandton Convention Centre 
The only residential house found to be investigated is in the western suburbs of 
Johannesburg. 
 House in western suburb of Johannesburg 
The first analysis of a green rooftop system is the DaVinci Hotel. 
Figure 7.2 is a photo of a green rooftop system on the DaVinci Hotel, indicating a green 
rooftop system in the form of planter boxes. 
 
Figure 7.2: Planter boxes on the DaVinci Hotel 
79 
 
The photo of a green rooftop system in Figure 7.2 is on the roof of the DaVinci Hotel.  
Various planter boxes have been built and filled with growing medium (compost).   
The vegetation consists out of flax plant species, cycads, hen-and-chickens, other shrubs 
and small trees.  Sprinklers are used to water the plants.  The planter boxes form part of the 
relaxation area of the roof. 
Figure 7.3 is a photo of a green rooftop system on the DaVinci Hotel illustrating the open 
space and relaxing area amongst the plants. 
 
 Figure 7.3: Relaxing space with green rooftop system on the DaVinci Hotel 
The photo of a green rooftop system in Figure 7.3 is on the roof of the DaVinci Hotel.  
Instead of the entire roof made into a green rooftop system, various planter boxes have been 
built and open spaces are present to utilise for relaxation purposes. 
The second analysis is the green rooftop system on The Michealangelo hotel. 
Figure 7.4 is a photo of a green rooftop system on The Michealangelo hotel. 
80 
 
 
Figure 7.4: Green rooftop system on The Michealangelo hotel 
The green rooftop system in Figure 7.4 is a photo of the roof of the The Michealangelo hotel.  
Instead of the entire roof made into a green rooftop systems, various planter boxes have 
been built and filled with growing medium and loose-standing pot plants.  The vegetation 
consists out of shrubs and small trees.  Sprinklers are used to water the plants.  The planter 
boxes form part of the relaxation area of the roof that provide the advantage to working 
people to relax and take a break from work.  The DaVinci Hotel and The Michealangelo have 
similar green rooftop systems.  Both have planter boxes with vegetation, which is mainly 
shrubs and small trees and open spaces to use for relaxing.    
The third roof that is investigated is the Sandton Convention Centre.  
Figure 7.5 is a photo of a green rooftop system on the Sandton Convention Centre. 
 
Figure 7.5: Green rooftop system on the Sandton Convention Centre 
81 
 
The green rooftop system as illustrated in a photo of the Sandton Convention Centre in 
Figure 7.5 is a green rooftop system on the roof and side of the building.  The vegetation 
consists out of flax species plants, other shrubs and small palm trees.  The planter boxes are 
not accessible to the public and are there for aesthetic reasons. 
The DaVinci Hotel and The Michealangelo have green rooftop systems on the roofs and is 
paired with relaxing space for individuals.  Sandton Convention Centre has vegetation on the 
side of the building and is for aesthetic purposes and not accessible to the public.  The three 
rooftop systems investigated are all semi-intensive green rooftop systems, but not in its 
entirety, as only sections of the roofs are covered with vegetation.  
The residential house investigated is in the western suburbs of Johannesburg. 
Figure 7.6 is a photo of a house in the western suburbs of Johannesburg with an extensive 
green rooftop system. 
 
Figure 7.6: Rooftop system on a residential house  
The green rooftop system of the photo, Figure 7.6, is an extensive green rooftop system of a 
house.  Part of the roof has been transformed into an extensive green rooftop system.  The 
vegetation is of grass which requires low maintenance.  The roof is not accessible for 
recreational or relaxation purposes.  
Not only commercial buildings have green rooftop systems, but residential houses as well. 
82 
 
7.4 CONCLUSION 
Field notes have been taken by observing three buildings in Sandton, Johannesburg with 
green rooftop systems.  The green rooftop systems are in the form of big planter boxes filled 
with growing medium.  The planter boxes are vegetated with shrubs and small trees, with 
loose standing pot plants.  The DaVinci Hotel and The Michealangelo use the vegetated 
space for recreational space and relaxing space.  Sandton Convention Centre has the 
vegetation on the side of the building and is for aesthetic reasons and is not accessible to 
the public.  The three commercial buildings investigated are all in Sandton which is a 
financial hub.  This indicates that green rooftop systems feature in affluent areas.  
Houses do not normally have green rooftop systems installed.  There is a house in the 
western suburbs of Johannesburg with an extensive green rooftop system.  The western 
suburbs of Johannesburg is an affluent area and therefore has the finances to install a green 
rooftop system. 
There are multiple roofs as illustrated in figure 7.1 with the potential for green rooftop 
systems in Johannesburg CBD.  From the highest skyscraper in Johannesburg CBD, 
multiple roofs are visible; however, none of the roofs have green rooftop systems.   
In the next chapter, the perspectives of South Africans regarding green rooftop systems are 
explored and analysed by means of empirical results.   
 
 
 
 
 
 
 
 
 
 
 
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CHAPTER 8: EMPIRICAL STUDY IN GREEN ROOFTOP SYSTEMS IN SOUTH AFRICA 
8.1 INTRODUCTION 
Questionnaires were sent out as the quantitative method to test the literature study. 
8.2 EMPIRICAL DATA 
The empirical data are presented in five parts.  Firstly, the profile of respondents, followed by 
sections 1 to 4, the South African perspective on green rooftop systems. 
8.2.1 Profile of respondents 
The questionnaires were sent to practising quantity surveyors, architects, engineers, 
contractors and citizens in Johannesburg, South Africa.   
The questionnaire were circulated to practising quantity surveyors, architects, engineers and 
contractors in the construction industry as well as citizens of Johannesburg by means of 
emails in order to determine the perspective of professionals and the public on green rooftop 
systems.  Johannesburg was chosen because it is the financial hub of South Africa and 
seems to be in the forefront of development.   
Table 8.1 indicates the various responding groups which consist of practising professionals 
in the construction industry and citizens of Johannesburg.  Column 1 indicates the 
profession of respondents; column 2 the number of questionnaires sent out to the respective 
groups; column 3 the number of questionnaires received back; column 4 the percentage of 
responses.     
Table 8.1: Profile of respondents 
Responding groups Questionnaires sent out Questionnaires received back Percentage
Contractors 2 2 100.00%
Quantity Surveyors 34 20 58.82%
Engineers 6 3 50.00%
Architects 7 3 42.86%
Citizens 110 40 36.36%
Total 159 68 42.77%  
A total of 159 questionnaires were sent out.  The response rate is 42.77% based on the 
questionnaires and is for the purpose of this study regarded as representative of the 
population.  The response is as follows; 100% of the contractors, 58.82% of quantity 
surveyors, 50% of engineers, 42.85% of architects and 36.36% of the citizens answered the 
questionnaire.  It is significant in respect of the reliability of the respons rate that 58.82% of 
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the responses received were from quantity surveyors.  However, the responses from the 
contractors did not distort the data.   
The quantity surveyors are seen as important respondents to this study because they give 
the professional opinions to the developers regarding cost and feasibility of developments.  
The response from the citizens are deemed important because these are needed to 
determine the demand and view from citizens about green rooftop systems.  
8.2.2 Section 1 Empirical Data 
 
Section 1 consists of 4 questions regarding green rooftop systems in South Africa.  The 
opinions of respondents were collected using a Likert scale of 1 to 5, where 1 is strongly 
disagree and 5 is strongly agree.  „None‟ represents the „not respond to the question‟. 
The purpose of the first 3 questions in section 1 were to determine the familiarity of green 
rooftop systems amongst professionals in the construction industry and citizens.  The aim of 
the question was to determine if there is a lack of knowledge in the construction industry 
regarding green rooftop systems.  
The result of the respondents regarding the familiarity of the concept of green rooftop 
systems are presented in table 8.2.  Column 1 lists the various responding groups, column 2 
reflects the none-responses, column 3 indicates the number of responses that are not 
familiar with the concept of green rooftop systems, column 4 indicates the number that are 
familiar and column 5 gives the percentage of the responses that are familiar with the 
concept of green rooftop systems.   
Table 8.2: Familiarity with green rooftop systems (Question 1.1) 
Familiarity with green rooftop systems None No Yes %
Architects 0 0 3 100.00%
Contractors 0 0 2 100.00%
Citizens 1 6 33 82.50%
Engineers 0 1 2 66.67%
Quantity Surveyors 0 9 11 55.00%
Total 1 16 51 68
Percentage of total 1.47% 23.53% 75.00%  
The data analysed regarding the familiarity of green rooftop systems indicate that 75.00% of 
the group were familiar with the concept of green rooftop systems and that 23.52% were not 
familiar with the concept.  What is noteworthy, is that  82.50% of the citizens were familiar 
with the concept.  What is concerning is that 55% of the quantity surveyors were familiar with 
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the concept;  100% of the architects; 100% of the contractors and 66.67% of the engineers 
were familiar with the concept of green rooftop systems. 
The data clearly indicate that citizens are familiar with the concept of green rooftop systems; 
however, the professionals are not that familiar.  Therefore, the professional members do not 
recommend green rooftop systems to be built and that contributes to why there are only a 
few green rooftop systems in South Africa.  This indicates that green rooftop systems are a 
relatively new concept in South Africa and need to be introduced to the citizens and 
construction industry. 
The results of question 1.2 regarding how many of the respondents have seen a green 
rooftop system in South Africa, indicate that 100% of the contractors had seen green rooftop 
systems and 66.67% of the architects had seen it.  However, only 40% of the quantity 
surveyors, 37.50% of citizens and 33.33% of engineers had seen it.  The citizens and 
engineers are familiar with the concept of green rooftop systems, but few had seen it.  The 
architects and contractors were familiar with the concept and had seen it.  Quantity 
surveyors however, were not familiar with the concept and only a few had seen green 
rooftop systems.  The data clearly indicate why there are only a few green rooftop system 
developments in Johannesburg, because of the lack of knowledge of the professional team.  
Green rooftop systems are not well known or seen in South Africa, as 57.35% of the 
respondents had never seen a green rooftop system in South Africa. 
In question 1.3 locations were given and divided into the nine provinces of South Africa.  The 
provinces are Gauteng, Western Cape, Kwa-Zulu Natal, Free State, Eastern Cape, Northern 
Cape, North West, Limpopo and Mpumalanga.  The results of Question 1.3 indicate the  
provinces were the respondents had seen green rooftop systems.   
The purpose of question 1.3 is to determine if citizens of Johannesburg had seen any green 
rooftop systems in other provinces in South Africa and where.  The data indicate that 
36.76% of the respondents had seen a green rooftop system in Gauteng; 10.29% in Western 
Cape; 1.47% in KwaZulu Natal; and 1.47% in Northern Cape; and 0% in the remaining 
provinces.    
The data gathered indicates, that green rooftop systems are widespread in South Africa and 
occurs in Gauteng, Western Cape, Kwa-Zulu Natal and Northern Cape.  Just over half of the 
respondents, 57.35%, had not seen a green rooftop system, before which indicates that the 
existing green rooftop systems are sparsely found and relatively unknown.  
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The type of green rooftop system that is feasible for South African circumstances was 
analysed next (question 1.4). 
There are different types of green rooftop systems.  The three types of green rooftop 
systems that are analysed in the study are the extensive system, semi-intensive system and 
intensive system.  Each system has different characteristics, therefore it is important to 
determine which system would be the most appropriate for South African circumstances. 
The purpose of this question was to determine which type of green rooftop system is the 
most feasible of the types for Johannesburg as such. 
The data of the extensive green rooftop system are as follows.  The result of the 
respondents regarding the extensive green rooftop system in South Africa are presented in 
table 8.3.  Column 1 lists the various responding groups; column 2 to 6 depicts the rating of 
the responses; 1 is strongly disagree; and 5 is strongly agree.  Column 7 is the none-
responses; column 8 is the total responses; column 9 is the average responses; and column 
10 gives the ranking. 
Table 8.3: Extensive green rooftop system in South Africa 
Rating                                                                  
Extensive 1 = strongly disagree        5 = strongly agree None Total Average Ranking
1 2 3 4 5
Citizens 4 3 9 9 14 1 40 3.67 1
Quantity Surveyors 5 3 3 4 5 0 20 3.05 2
Engineers 1 1 1 0 0 0 3 2.00 3
Contractors 1 0 1 0 0 0 2 2.00 3
Architects 2 0 1 0 0 0 3 1.67 4
Total 13 7 15 13 19 1 68 3.27
Percentage of Tot 19.12% 10.29% 22.06% 19.12% 27.94% 1.47% 100.00%  
The data analysed indicate that the average of the respondents‟ opinion is 3.27; that is 
according to the Likert scale, between „neutral‟ and „agree‟ for the extensive green rooftop 
system in South Africa.  The results are citizens (3.67), quantity surveyors (3.05), engineers 
(2.00), contractors (2.00) and architects (1.67).  The citizens and quantity surveyors are 
ranked first and second with 3.67 and 3.05 respectively.  The architects disagreed (1.67) and 
are ranked the lowest with the extensive green rooftop system being appropriate for South 
African circumstances.  Thus, the citizens and quantity surveyors regarded the extensive 
green rooftop system to be feasible for South African circumstances.  . 
The data regarding the semi-intensive green rooftop system were also analysed.   
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The results of the respondents‟ answers regarding the semi-intensive green rooftop system 
in South Africa are given in table 8.4.  Column 1 lists the various responding groups; 
columns 2 to 6 depict the rating of the responses, where 1 is strongly disagree and 5 is 
strongly agree.  Column 7 reflect the none-responses, column 8 the total responses, column 
9 the average responses and column 10 the ranking. 
Table 8.4: Semi-Intensive green rooftop system in South Africa  
Rating                                                                  
Semi-Intensive 1 = strongly disagree        5 = strongly agree None Total Average Ranking
1 2 3 4 5
Contractors 0 0 0 1 1 0 2 4.50 1
Engineers 0 0 1 1 1 0 3 4.00 2
Citizens 1 2 17 12 7 1 40 3.56 3
Quantity Surveyors 1 1 8 8 2 0 20 3.45 4
Architects 1 0 1 0 1 0 3 3.00 5
Total 3 3 27 22 12 1 68 3.55
Percentage of Tot 4.41% 4.41% 39.71% 32.35% 17.65% 1.47% 100.00%
 
The data analysed indicate that the average of the respondents‟ opinions is 3.55; that is 
according to the Likert scale between „neutral‟ and „agree‟ for the semi-intensive green 
rooftop system in South Africa.    The results are contractors (4.50), engineers (4.00), 
citizens (3.56), quantity surveyors (3.45) and architects (3.00).  The engineers and 
contractors are ranked first and second and the architects are ranked the lowest.   
Although the averages of the groups differs, the general tendency is that semi-intensive 
green rooftop systems represent a feasible type of green rooftop  system for South African 
circumstances.   
The data of the intensive green rooftop system were analysed as well.   
The results of the respondents‟ views regarding the intensive green rooftop system in South 
Africa is illustrated in table 8.5.  Column 1 lists the various responding groups; column 2 to 6 
depict the rating of the responses, where 1 is strongly disagree and 5 is strongly agree.  
Column 7 reflects the none-responses, column 8 total responses, column 9 average 
responses and column 10 the ranking. 
 
 
 
 
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Table 8.5: Intensive green rooftop system in South Africa  
Rating                                                                  
Intensive 1 = strongly disagree        5 = strongly agree None Total Average Ranking
1 2 3 4 5
Engineers 1 0 0 0 2 0 3 3.67 1
Contractors 0 0 2 0 0 0 2 3.00 2
Citizens 12 8 9 6 4 1 40 2.54 3
Quantity Surveyors 6 8 5 1 0 0 20 2.05 4
Architects 2 0 1 0 0 0 3 1.67 5
Total 21 16 17 7 6 1 68 2.42
Percentage of Tot 30.88% 23.53% 25.00% 10.29% 8.82% 1.47% 100.00%  
The data analysed indicate that the average of the respondents‟ opinions is 2.42; that is, 
according to the Likert scale between „disagree‟ and „neutral‟ for the intensive green rooftop 
system in South Africa.  The results are engineers (3.67), contractors (3.00), citizens (2.54), 
quantity surveyors (2.05) and architects (1.67).  The contractors and engineers are ranked 
first and second and are neutral about the feasibility of the intensive green rooftop system 
and the architects‟ opinion is that it is not feasible and is ranked the lowest.   
The comparison of the the three types of green rooftop systems, i.e. extensive, semi-
intensive and intensive system, is presented in table 8.6.  Column 1 lists the type of green 
rooftop systems, column 2 presents the citizens, column 3 presents the quantity surveyors, 
column 4 presents the engineers, column 5 presents the architects, column 6 presents the 
contractors, column 7 reflects the average of the four professional groups and citizens, 
column 8 reflects the percentage and column 9 the ranking. 
Table 8.6: Comparison of type of green rooftop systems  
Comparison of the types of Rooftop Systems Citizens QS Eng. Arch Con. Average % Ranking
Semi-Intensive 3.56 3.45 4.00 3.00 4.50 3.55 71.04% 1
Extensive 3.67 3.05 2.00 1.67 2.00 3.27 65.37% 2
Intensive 2.54 2.05 3.67 1.67 3.00 2.42 48.36% 3  
The data regarding the comparison of the three types indicate that the semi-intensive green 
rooftop system is ranked 1st as a feasible type of green rooftop system, the extensive green 
rooftop system is ranked 2nd and the intensive green rooftop system is ranked 3rd.  The 
contractors (4.50) felt the strongest about the semi-intensive green rooftop system being the 
most feasible type of system for South Africa.  The citizens‟ (3.67) responses indicate that 
extensive green rooftop system is the most feasible type of system for South Africa and the 
engineers (3.67) were of the opinion that the intensive green rooftop system is feasible for 
South Africa.   
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The semi-intensive green rooftop system is the most feasible for South African 
circumstances of the three types of systems.  The extensive green rooftop system may also 
be considered, but the intensive green rooftop system is not feasible according to the 
results. 
8.2.3 Section 2 Empirical Data 
Section 2 consists of nine questions regarding the effects of green rooftop systems in cities.  
The opinions of respondents were collected using a Likert scale of 1 to 5 where 1 is strongly 
disagree and 5 is strongly agree.  The opinions of the different professions and citizens were 
analysed separately and in combination and both the combined data and separate data are 
the same; thus the data of the different professions did not distort  the results.     
There were 4 purposes with the questions in section 2.  Purpose one was to determine 
which factors or effects that green rooftop systems have on the surroundings in cities will 
encourage the development of green rooftop systems.  The second purpose was to 
determine what factors will bo of benefit to Johannesburg as city.  The third purpose is to 
determine the level of appreciation and utilization of existing open parks in Johannesburg 
and the forth purpose was to determine if there is a demand for green rooftop systems in 
Johannesburg.   
The combination of the results regarding the different factors influencing the development of 
green rooftop systems is given in table 8.7.  Column 1 lists various elements encouraging 
development, column 2 presents the average rating, column 3 reflects the percentage and 
column 4 the ranking. 
 
 
 
 
 
 
 
 
 
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Table 8.7: Factors influencing the development of green rooftop systems 
Elements encouraging development Average % Ranking
Improved air quality 4.04 80.88% 1
Aesthetics 3.96 79.12% 2
Recreational space 3.90 77.94% 3
Habitats 3.82 76.47% 4
Job creation 3.76 75.29% 5
Heat Island effect 3.75 75.00% 6
Increasing property value 3.68 73.53% 7
Storm water management 3.68 73.53% 7
Insulation 3.62 72.35% 8
Agriculture 3.47 69.41% 9
Secure and safe 3.35 67.06% 10
Demand 3.34 66.76% 11
Sound Insulation 3.33 66.60% 12
Identity 3.18 63.53% 13
Privacy 3.04 60.88% 14
Life extention of roof membrane 3.03 60.59% 15
Belonging 2.99 59.71% 16
Memory 2.91 58.24% 17  
The results indicate that improved air quality (80.88%) is ranked first, aesthetics (79.12%) is 
ranked second, recreational space (77.94%) is ranked third, habitats (76.47%) fourth, job 
creation (75.29%) fifth, heat island effect (75.00%) sixth, increasing property value (73.53%) 
and storm water management (73.53%) seventh, insulation (72.35%) eighth, agriculture 
(69.41%) ninth, secure and safe (67.06%) tenth, demand (66.76%) eleventh, sound 
insulation (63.53%) twelfth, identity (60.88%) thirteenth, privacy (60.59%) fourteenth, life 
extension of roof membrane (60.88%) fifteenth, belonging (59.71%) sixteenth and memory 
(58.24%) last.  
Improved air quality emerged as an important factor that may encourage the development of 
green rooftop systems.  The second to fifth important factors are aesthetics, recreational 
space, habitats and job creation, which may encourage the development of green rooftop 
systems.   
Heat island effect, increasing property value, storm water management and insulation are 
factors that may encourage the development of green rooftop system, but to a lesser extent.  
Agriculture, secure and safe, demand, sound insulation, identity, privacy, life extension of 
roof membrane, belonging and memory are factors that are seen as less important and do 
not seem to encourage green rooftop systems as such.   
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The combination of the results regarding the different factors influencing the development of 
green rooftop systems is illustrated in table 8.8.  Column 1 lists various advantages of green 
rooftop systems that Johannesburg may benefit from, column 2 presents the average, 
column 3 reflects the percentage and column 4 the ranking. 
Table 8.8: Elements benefitting Johannesburg  
Elements benefitting Johannesburg Average % Ranking
Improved air quality 4.21 84.12% 1
Insulation 4.09 81.76% 2
Job creation 3.96 79.12% 3
Aesthetics 3.79 75.88% 4
Heat island effect 3.76 75.29% 5
Storm water management 3.75 75.00% 6
Economic Growth 3.75 75.00% 6
Increasing property value 3.74 74.71% 7
Recreational space 3.72 74.41% 8
Habitats 3.68 73.53% 9
Sound insulation 3.63 72.65% 10
Life extention of roof membrane 3.53 70.59% 11
Agriculture 3.51 70.29% 12
Secure and safe 3.49 69.71% 13
Privacy 3.28 65.59% 14  
The data analysed indicate that improved air quality (84.12%) is ranked first, insulation 
(81.76%) second, job creation (79.12%) third, aesthetics (75.88%) fourth, heat island effect 
(75.29%) fifth, storm water management (75.00%) and economic growth (75.00%) sixth, 
increased property value (74.71%) seventh, recreational space (74.41%) eighth, habitats 
(73.53%) ninth, sound insulation (72.65%) tenth, life extension of roof membrane (70.59%) 
eleventh, agriculture (70.29%) twelve, secure and safe (69.71%) thirteenth and privacy 
(65.59%) fourteenth.    
It seems that Johannesburg may benefit the most from the improved air quality offered by 
green rooftop systems.  The elements that stand out from which Johannesburg will benefit is 
improved air quality, better insulated buildings, job creation, aesthetics, eliminating the heat 
island effect, stormwater management and economic growth.  Increased property value, 
recreational space, habitats, sound insulation, life extension of roof membrane and 
agriculture are elements which Johannesburg may benefit from; however, to a lesser extent 
than the top five elements.  Secure and safe area and privacy are less important factors for 
Johannesburg according to the results.    
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The results of table 8.7 and table 8.8 in conjunction provide important results that may 
contribute to finding the relevant elements to Johannesburg as such.  Improved air quality, 
job creation and aesthetics are three elements that encourage the development of green 
rooftop systems as well as being beneficial to Johannesburg.  Thus, the three elements may 
be regarded as the components that may encourage professionals and citizens to develop 
green rooftop systems in the Johannesburg area. 
Question 2.3 determined how many of the respondents live or work within a close proximity 
(1km) of a green area.  The purpose of question 2.3 was to determine how far the 
respondents live or work from green areas.  According to the data, 73.53% of the 
respondents live or work within 1km from a green area and 26.47% do not; thus, mostly the 
respondents do have access to green areas. 
The purpose of Question 2.4 was to determine the level of utilization of the parks.  The data 
analysed from the respondents is an average of 2.38 which is between „almost never‟ and 
„sometimes‟ on the likert scale.  The respondents indicate that they never (30.88%) and 
almost never (22.02%) utilize the parks.  Thus, although respondents live or work near green 
areas, they never or almost never utilize these parks.   
The purpose of question 2.5  was to determine the reasons for not utilizing the parks in order 
to determine if green rooftop systems might contribute to the solution.   
The results regarding the reasons for not utilizing green areas in Johannesburg is presented 
in table 8.9.  Column 1 lists various factors that may keep citizens from going to parks, 
column 2 presents the average rating, column 3 reflects the percentage and column 4 the 
ranking. 
Table 8.9: Reasons for not utilizing parks 
Factors driving Johannesburgers away from parks Average result % Ranking
Crime 3.55 70.91% 1
Unsafe 3.53 70.61% 2
Lack of maintenance 3.02 60.30% 3
Filthy and littered 2.98 59.70% 4
Lack of privacy 2.83 56.67% 5  
The main reason for not utilizing green areas is crime (70.91%). The second reason is 
unsafeness (70.61%), lack of maintenance (60.30%) is ranked third, filthy and littered 
(59.70%) is fourth and lack of privacy (56.67%) last.   
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The parks seem to be hot spots for crime and is generally unsafe; the two main factors that 
keep Johannesburg citizens away from green areas.  The lack of maintenance also 
contributes to keeping people away from parks, but to a lesser degree than crime and 
unsafeness.  Filthy and littered parks and lack of privacy is rarely the reason that keeps 
Johannesburg citizens away from green areas. 
The respondents rate „secure and safe‟ as an element to be a benefit to Johannesburg 
as13th (tabel 8.8) of importance of 14 elements, but crime and unsafeness as reasons for 
not utilizing Johannesburg parks as the highest.  Therefore, Johannesburg may benefit from 
green roof systems in that regard. 
Question 2.6 tests if Johannesburg is a sustainable city.  The purpose of the question is to 
determine the sustainability of Johannesburg without green rooftop systems.  The results 
received from the respondents is an average of 2.66 which is between „disagree‟ and 
„neutral‟ on the Likert scale.   
From the views of the respondents, it may be concluded that Johannesburg is not a 
sustainable city.  Therefore green rooftop systems may be a viable option in order to 
contribute to the sustainability of the city. 
Health is another benefit provided by vegetated spaces.  The purpose of question 2.7 was to 
determine to what degree green spaces contribute to the health of the respondents.  Various 
health benefits were explored in order to determine to what degree vegetated spaces 
contributes to health.  The results regarding the health benefits provided by vegetated 
spaces is given in table 8.10.  Column 1 lists various health benefits, column 2 presents the 
average rating, column 3 reflects the percentage and column 4 the ranking. 
Table 8.10: Health benefits from vegetated spaces 
Health benefits from green spaces in cities as seen Average result % Ranking
by Johannesburgers
Promoting health 4.03 80.59% 1
Decreasing stress 4.01 80.29% 2
Reducing depression 3.62 72.35% 3
Reducing anxiety 3.60 72.06% 4
Improving worker productivity 3.50 70.00% 5
Reducing patient recovery time 3.29 65.88% 6  
Promoting health (80.59%) is ranked first, decrease stress (80.29%) is ranked second, 
reducing depression (72.35%) third, reducing anxiety (72.06%) fourth, improving worker 
productivity (70.00%) fifth and reducing patient recovery time (65.88%) last.   
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The two health benefits from green areas are promotion of health and decreasing stress.  
Reducing depression, reducing anxiety, improving worker productivity and reducing patient 
recovery time seem to be benefits of green areas, but to a lesser degree.     
Green areas seem to have various health benefits.  The health benefits might encourage 
people to prioritize living or working within a close proximity of green areas.   
The aim of question 2.8 was to determine if respondents would prioritize living and or 
working close to green areas due to the health benefits. 
According to the data analysed, 77.94% of the respondents would prioritize living and or 
working close to green areas because of the health benefits that the green areas offer.  
Health seems to be an important factor to the respondents and most respondents (77.94%) 
would prioritize living and/or working within close proximity of green areas.  Green areas are 
thus important to the respondents, although most of them did not want to utilize these areas 
due to crime and unsafeness.   
Question 2.9 was asked to determine the rentability of residences with green rooftop 
systems in Johannesburg.  The aim of the question was to determine if tenants would pay 
more for property with green roof systems.  The respondents indicated that 76.47% would 
rather pay more in order to live in an apartment in a building with an exclusive green area 
and 23.53% would not pay more rent.  The majority of respondents were willing to pay for 
exclusive green areas.  The deduction, therefore is that there is a demand for green areas 
such as green rooftop systems and developments may still be feasible because tenants are 
willing to pay for it. 
8.2.4 Section 3 Empirical Data 
Section 3 consists of five questions regarding construction of green rooftop systems.  The 
opinions of respondents were analysed using a Likert scale of 1 to 5 where 1 is strongly 
disagree and 5 is strongly agree.  The opinions of the different professions and citizens were 
analysed separately but did not distort the data.     
There are three purposes with the questions in section 3.  Purpose one was to determine the 
knowledge and experience of the professionals in the construction industry regarding the 
construction of green rooftop systems.  Purpose 2 was to determine what factors may hinder 
the development of green rooftop systems and the third purpose was to determine what 
ways would be effective to encourage the development of green rooftop systems in South 
Africa. 
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The purpose of question 3.1 was to determine how many of the respondents had experience 
with the construction of green rooftop systems.  The results of the respondents were 
analysed to determine the experience of the respondents in the construction of green rooftop 
systems and are presented in table 8.11.  Column 1 lists the various responding groups, 
column 2 presents the number of respondents that had experience with the construction of 
green rooftop systems, column 3 indicate the number of respondents that had no experience 
with the construction of green rooftop systems and column 4 is the total.   
Table 8.11: Experience in constructing green rooftop systems 
Experience in constructing green rooftop systems Yes No Total
Citizens 0 40 40
Subtotal - None Proffessionals 0 40 40
Percentage of subtotal 0.00% 100.00% 100.00%
Quantity Surveyors 1 19 20
Architects 2 1 3
Engineers 0 3 3
Contractors 0 2 2
Subtotal - Proffesional team members in construction industry 3 25 28
Percentage of subtotal 10.71% 89.29% 100.00%
Total 3 65 68
Percentage of total 4.41% 95.59% 100%  
According to the data analysed, as many as 95.59% of the respondents had no experience 
in the construction of green rooftop systems.  The data clearly indicate that a lack of 
experience in the construction of green rooftop systems is a problem and that the 
professional members did not have experience, and therefore did not advise on construction 
of green rooftop systems.     
The results regarding the factors to take into consideration when constructing a green 
rooftop system are illustrated in table 8.12. The purpose of question 3.2 was to determine 
what factors are important to take into consideration when aiming to construct a green 
rooftop system.  Column 1 lists various factors to take into consideration with the 
construction of green rooftop systems, column 2 presents the average rating, column 3 
reflects the percentage and column 4 the ranking. 
 
 
 
 
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Table 8.12: Factors to consider when constructing a green rooftop system  
Factors to take into consideration when Average result % Ranking
constructing a green rooftop system
Drainage 4.44 88.82% 1
Weight loading 4.35 87.06% 2
Location and climate 4.24 84.71% 3
Water usage problems 4.22 84.41% 4
Access to the roof 4.09 81.76% 5
Availability of the materials 3.94 78.82% 6
Professional consultants 3.81 76.18% 7
Specializing suppliers 3.75 75.00% 8  
The analyses of the response from the respondents is that drainage (88.82%) is the most 
important factor to take into consideration when constructing a green rooftop system.  
Secondly weight loading (87.06%), thirdly location and climate (84.71%), fourthly water 
usage problems (84.41%), fifthly access to the roof (81.76%), sixthly availability of the 
materials (78.82%), seventhly professional consultants (76.18%) and lastly specializing 
suppliers (75.00%).    
The two factors that need to be taken into consideration when constructing a green rooftop 
system are drainage and weight loading.  Both drainage and weight loading are elements 
that may cost money when it needs to be altered for green rooftop systems.  It seems that 
the most important factors that need to be considered is the factors that will have a financial 
impact.   Drainage, weight loading, location and climate, water usage problems, access to 
the roof, availability of the materials, professional consultants and specializing suppliers are, 
however, important factors to take into consideration as per the response from the 
respondents.  The factors do not vary more than 13.82%, which may indicate that all the 
factors are important to the respondents. 
South Africa has water shortage problems and gardens require water, different options need 
to be explored in order to solve the water shortage problem.  The purpose of question 3.3 
was to determine what options would be best preferred when taking water shortage into 
account.   
The results regarding the different options to manage water shortage problems together with 
green rooftop systems are provided in table 8.13.  Column 1 lists various options to work 
around water shortage problems, column 2 presents the average rating, column 3 reflects 
the percentage and column 4 the ranking. 
 
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Table 8.13: Options to consider when water is a problem in South Africa 
Alternative options when faced with water shortage Average result % Ranking
Gather storm water 4.37 87.35% 1
Recycle building water 4.25 85.00% 2
Choose vegetation indigenous to location and climate 4.01 80.29% 3
No green rooftops 2.04 40.88% 4  
Gather stormwater (87.35%) is ranked first as an option to consider when water in South 
Africa is a problem, recycle building water (85.00%) is ranked second, choose vegetation 
indigenous to location and climate (80.29%) third and no green rooftop systems (40.88%) 
last.    
Gathering of stormwater seems to be the respondents‟ first option in order to compensate for 
water shortage.  Recycled water and indigenous vegetation, however, are also definite 
viable options to compensate for water shortage.  The respondents indicated that no green 
roofs is not an option to solve water problems.   
Green rooftop systems seem to come with disadvantages that might limit the development 
thereof.  Question 3.4 lists some of these disadvantages.  The data analysed regarding the 
factors limiting the development of green rooftop systems are given in table 8.14.  Column 1 
lists various limiting factors to the development of green rooftop systems, column 2 presents 
the average rating, column 3 reflects the percentage and column 4 the ranking. 
Table 8.14: Factors limiting the development of green rooftop systems 
Factors limiting the development of green roof Average % Ranking
systems
Structural integrity 4.10 82.06% 1
High cost 3.99 79.71% 2
Maintenance 3.46 69.12% 3
Vermin problem 3.31 66.18% 4  
The data analysed indicated that structural integrity (82.06%) is ranked first, high cost 
(79.71%) second, maintenance (69.12%) third and vermin problem (66.18%) last.    
Structural integrity seems to be the most important factor that may limit the development of 
green rooftop systems, as well as high cost.  Maintenance and pest problems are ranked 
lower and are less important factors that may limit the development of green rooftop systems 
in contrast with structural integrity and high cost.  
Green rooftop systems is a relative new concept in South Africa and the development 
thereof need to be encouraged.  There seems to be various ways of encouraging the growth 
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of certain developments.  Question 3.5 state different methods to encourage the 
development of green rooftop systems in South Africa, specifically Johannesburg.     
The results regarding the different ways to encourage the development of green rooftop 
systems in South Africa are presented in table 8.15.  Column 1 lists ways to implement the 
development of green rooftop systems, column 2 presents the average rating, column 3 
reflects the percentage and column 4 the ranking. 
Table 8.15: Encouraging the development of green rooftop systems in South Africa 
Ways to implement green roof systems in South Average result % Ranking
Africa
Incentives 4.12 82.35% 1
Public buildings as displays 3.99 79.71% 2
Municipal grants 3.93 78.53% 3
Building regulations 3.84 76.76% 4
State legislation 3.69 73.80% 5
Competitions and awards 3.46 69.12% 6
Communication, negotiation and persuasion 3.21 64.12% 7  
The data indicate that incentives (82.35%) is ranked first as a way to implement green 
rooftop systems in South Africa for development.  Public buildings as displays (79.71%) is 
ranked second, municipal grants (78.53%) third, building regulation (76.76%) fourth, state 
legislation (73.80%) fifth, competitions and awards (69.12%) sixth and communication, 
negotiation and persuasion (64.12%) last as ways to implement green rooftop systems in 
South Africa for development.  
Incentives seem to encourage the development of green rooftop systems the most in South 
Africa according to the respondents.  Public buildings as displays, municipal grants, building 
regulations and state legislation seems to be grouped secondly as ways that would 
encourage the development of green rooftop systems in South Africa.  Competitions and 
awards and communication, negotiation and persuasion seem to be less successful ways to 
encourage green rooftop systems in South Africa.  Thus, incentives may be the most 
important way to develop green rooftop systems in South Africa, specifically Johannesburg. 
8.2.5 Section 4 Empirical Data 
Section 4 consists of two questions regarding vegetation to green rooftops in South Africa, 
but more specifically Johannesburg.  The data of respondents were collected using a Likert 
scale of 1 to 5 where 1 is strongly disagree and 5 is strongly agree.  The opinions of the 
different professions and citizens were analysed separately but did not distort the data.     
99 
 
The purpose of this section was to determine which of the list of indigenous plants are 
preferred by the respondents for green roofs in Johannesburg.  Plants have different 
characteristics, therefore it seems necessary to determine the characteristics best suitable 
for rooftops in South Africa. 
The data analysed regarding the different characteristics that seem to be the best suitable 
for rooftops in South Africa are illustrated in table 8.16.  Column 1 lists preferred 
characteristics of plants, column 2 the average rating, column 3 reflects the percentage and 
column 4 the ranking. 
Table 8.16: Preferred characteristics for rooftop plants 
Preferred characteristics of plants on roofs Average result % Ranking
Little maintenance required 4.39 87.76% 1
Aesthetic 4.33 86.57% 2
Draught resistant 4.13 82.69% 3
Heat resistant 4.13 82.69% 3
Indigenous 4.07 81.49% 4
Wind resistant 4.00 80.00% 5
Hardy 3.97 79.40% 6  
The characteristic that seems to be the most important and ranked first is little maintenance 
required (87.76%), aesthetic (86.57%) is ranked second, drought resistant (82.69%) and 
heat resistant (82.69%) third, indigenous (81.49%) fourth, wind resistant (80.00%) fifth and 
hardy (79.40%) last.   
Little maintenance seems to be the characteristic that respondents prefer most for plants to 
be on green rooftop systems.  However, the characteristics aesthetic, resistant, heat 
resistant, indigenous, wind resistant and hardy are important to the respondents and may be 
preferred for green rooftop systems. 
In question 4.2 indigenous plants that may be suitable for rooftop conditions in 
Johannesburg were presented to the respondents in order to determine which of the plants 
might be the best plants to use with green rooftop systems. 
The analysed data regarding the different plants are given in table 8.17.  Column 1 lists 
different plants, column 2 presents the average rating for the entire group, column 3 reflects 
the percentage and column 4 the ranking. 
 
 
100 
 
Table 8.17: Preferred plants for rooftops  
Preferred plants for rooftops Average result % Ranking
Kranz Aloe 3.75 75.00% 1
Soap Aloe 3.66 73.13% 2
Klipsalie 3.58 71.56% 3
Lemon thorn 3.48 69.69% 4
Pineapple lily 3.41 68.13% 5
Meelplakkie 3.39 67.81% 6
Porkbush 3.28 65.63% 7
Drooping agapanthus 3.25 65.00% 8
Doll's powderpuff 3.25 65.00% 8
Snake flower 3.17 63.44% 9
Slymstok 3.14 62.81% 10  
The data analysed indicate that Kranz Aloe (75.00%) is ranked first, Soap Aloe (73.13%) 
second, Klipsalie (71.56%) third, Lemon thorn (69.69%) fourth, Pineapple lily (68.13%) fifth, 
Meelplakkie (67.81%) sixth, Porkbush (65.63%) seventh, Drooping agapanthus (65.00%) 
and Doll‟s powderpuff (65.00%) eighth, Snake flower (63.44%) ninth and Slymstok (62.81%) 
last as preferred plants.  
The aloes, Kranz Aloe and Soap Aloe, and Klipsalie seems to be the most popular plants 
amongst the respondents to plant on green rooftop systems.  Lemon thorn, Pineapple lily, 
Meelplakkie, Porkbush, Drooping agapanthus, Doll‟s powderpuff, Snake flower and Slymstok 
are less popular than the Aloes and Klipsalie, but are, however, still acceptable by the 
respondents to plant as rooftop plants. 
8.3 CONCLUSION 
The questionnaire was circulated to practising quantity surveyors, architects, engineers and 
contractors in the construction industry as well as citizens of Johannesburg by means of 
email.  The response rate was 42.77%.  
The respondents indicated that they were familiar with green rooftop systems, yet citizens 
seem to be more familiar with the concept of green rooftop systems than the professionals.   
Green rooftop systems are not well known or seen in South Africa, as 57.35% of the 
respondents had never seen a green rooftop system in South Africa.  Some of the 
respondents had seen green rooftop systems in Gauteng, Western Cape, KwaZulu Natal 
and Northern Cape.   
101 
 
Regarding the type of green rooftop systems, the respondents considered that the semi-
intensive green rooftop system to be the most feasible for South African circumstances and 
intensive green rooftop system to be not feasible at all. 
Improved air quality emerged as an important factor that may encourage the development of 
green rooftop systems.  The second to fifth important factors are aesthetics, recreational 
space, habitats and job creation that may encourage the development of green rooftop 
systems.   
It seems that Johannesburg may benefit the most from the improved air quality offered by 
green rooftop systems.  The elements that stand out from which Johannesburg seems to 
benefit are improved air quality, better insulated buildings, job creation, aesthetics and 
eliminating the heat island effect.      
Improved air quality, job creation and aesthetics are three elements that encourage the 
development of green rooftop systems as well as being beneficial to Johannesburg.  Thus, 
the three elements may be regarded as the components that may encourage professionals 
and citizens to develop green rooftop systems in the Johannesburg area. 
The data indicate that 73.53% of the respondents live and or work within 1km of a green 
area, although they do not make use of these areas due to reasons such as crime and 
general unsafeness.  The respondents indicate that they do no utilize the green areas, but 
these areas may contribute to the promotion of health, decreasing stress,  reducing 
depression, reducing anxiety and improving worker productivity.  The majority of the 
respondents were however willing to pay more for property with a green rooftop system.     
The respondents indicated that they did not have any experience in the construction of green 
rooftop systems, but that factors such as drainage and weight loading need to be taken into 
consideration when constructing a green rooftop system.  Regarding the problem of water 
shortage, the respondents indicated that gathering of stormwater, recycled water and 
indigenous vegetation would rather be considered than not developing green rooftop 
systems.   
Structural integrity seems to be the most important factor that may limit the development of 
green rooftop systems as well as high cost, but incentives may encourage the development.   
The respondents indicated that the type of plants preferred for green rooftop systems are 
those that require little maintenance.  Plants that are aesthetically pleasing, resistant, heat 
resistant, indigenous, wind resistant and hardy are important, to be successful on the 
102 
 
rooftops of buildings.  The preferred plants are the aloes, Kranz Aloe and Soap Aloe, and 
Klipsalie that seem to be the most popular plants according to the respondents.   
In Chapter 9, the summary of the study, findings and conclusions, as well recommendations 
for further research are presented. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
103 
 
CHAPTER 9: CONCLUSION AND RECOMMENDATION 
9.1 INTRODUCTION 
The study consists of an introduction to study, a literature review, empirical section, findings 
and conclusions.   
9.2 SUMMARY OF STUDY 
The problem of the study is as follows: Rooftop gardens are not getting the recognition for 
their value to the environment, the citizens, the industry and the buildings as such in South 
Africa.  This is due to lack of knowledge and innovation.      
In Chapter 2 the history of green rooftop systems worldwide was reviewed.  The anatomy of 
green rooftop systems were reviewed as well as the different types of green rooftop 
systems.  The types of green rooftop systems are extensive, semi-intensive and intensive.  A 
comprehensive comparison was done as this might contribute to the decision making as to 
what green rooftop system to install.   
In Chapter 3, the possible effects of green rooftop systems to the surroundings and 
environment were reviewed.  The advantages are insulation to a building, extension of roof 
membrane, sound insulation, slowing down the spread of fire, retain stormwater, mitigate the 
urban heat island effect, create habitats, food production, recreational space, increase air 
quality, increase property values, reduces stress, reduces patient recovery time, improves 
worker productivity.  Building regulations may need to be amended to encourage the 
development of green rooftop systems. 
In Chapter 4, the design and construction of a green rooftop system were reviewed.  The 
factors to take into consideration when constructing a green rooftop system are the location 
and climate, weight loading, the professional team needed, drainage and access to the roof.  
The materials needed to construct a green rooftop system were reviewed as well as the 
availability of the materials in South Africa.  
In Chapter 5, indigenous plant species were identified that may thrive on rooftops in South 
Africa and more specifically Johannesburg.  
In Chapter 6, the research design and methodology were presented.  The research data 
were collected by quantitative and qualitative methods.  Field notes were taken as the 
qualitative method and questionnaires were sent out as the quantitative method to analyse 
data.  
104 
 
Chapter 7 presented the field notes of existing green rooftop systems in the Johannesburg 
area. 
Chapter 8 presented the empirical findings to determine the South African perspective on 
green rooftop systems. 
9.3 FINDINGS 
9.3.1 First hypothesis 
The first hypothesis of the study is as follows: 
Green rooftop systems is a new concept in South Africa and underdeveloped.  
The hypothesis was shown to hold.  The literature and empirical data confirmed that green 
rooftop systems is a new concept in South Africa and underdeveloped.  The citizens among 
the respondents were familiar with the concept of green rooftop systems but the 
professionals among the respondents less so.   Only a few respondents had seen a green 
rooftop system in South Africa.  Green rooftop systems had, however, been seen in 
Gauteng, Western Cape, KwaZulu Natal and Northern Cape.   
The respondents did not have experience regarding the construction of green rooftop 
systems, and thus indicated why professional members of the construction industry did not 
recommend the development thereof.  This further indicates that there is a lack of knowledge 
in the industry regarding the construction of green rooftop systems and the benefits that 
accompany green rooftop systems.  Despite the lack of knowledge in the industry, the 
materials needed to construct green rooftop systems are available in South Africa.   
9.3.2 Second hypothesis 
The second hypothesis of the study is as follows: 
South Africa, and specifically Johannesburg, will benefit from the development of 
green rooftop systems, despite water shortage.   
The hypothesis was proven correct.  Johannesburg seems to benefit most from improved air 
quality and better insulated buildings.  Other benefits also include job creation, aesthetics, 
eliminating the heat island effect, stormwater management and economic growth.  
Respondents do not utilise existing green areas due to crime and unsafeness, and green 
rooftop systems provide a secure and safe green area.  Green areas also provide health 
benefits such as promotion of health, reducing stress, depression and anxiety.  
105 
 
Despite water shortage, green rooftop systems may still be developed as the respondents 
would rather consider alternative options such as the gathering of storm water, recycled 
water of the building and indigenous vegetation accustomed to the climate because of the 
benefits provided by having green rooftop systems.      
9.3.3 Third hypothesis 
The third hypothesis of the study is: 
There is a demand for green rooftop systems in South Africa and the developments 
thereof will be feasible. 
The hypothesis was shown to hold.  The majority of the respondents indicated that they are 
willing to pay more rent for a property with a green rooftop system.  They also indicated that 
it is a priority for them to live and or work in a close proximity of green areas due to the 
health benefits.  Therefore there is a demand for green rooftop systems in Johannesburg.   
Drainage and structural integrity are important factors that may limit the development of 
green rooftop systems due to the financial impact.  Incentives seem to be the best way to 
encourage the development of green rooftop systems according to the respondents.  
Therefore, finance is a concern for the development of green rooftop systems in South 
Africa, however, there is a demand for it as the respondents are willing to pay more rent for 
property with green areas.  Property value thus increases with the development of green 
rooftop systems and absorbs the financial impact thereof.   
There are different types of green rooftop systems with different cost implications and 
according to the respondents the semi-intensive green rooftop system will be feasible for 
South African circumstances.  The field notes presented that the few existing green rooftop 
systems in Johannesburg are semi-intensive green rooftop systems.  
9.3.4 Fourth hypothesis 
The fourth hypothesis of the study is as follows: 
Green rooftop systems will conserve indigenous plant species. 
The hypothesis was proven correct.  The literary review indicates that conditions on rooftops 
require plants to be hardy, drought resistant, heat resistant and wind resistant in order to be 
successful; the respondents agreed with this.  The respondents also preferred plants for 
rooftops to require little maintenance, be aesthetically pleasing and indigenous.  The literary 
review indicates that there are indigenous plants that may be successful on rooftops.  The 
106 
 
respondents indicated that they prefer Kranz Aloes, Soap Aloes and Klipsalie.  Green 
rooftop systems may thus conserve indigenous plant species and create habitats.   
9.4 CONCLUSION 
Green rooftop systems represent a new concept in South Africa that is underdeveloped due 
to a lack of knowledge in the construction of green rooftop systems and a lack of knowledge 
regarding the benefits provided by green rooftop systems to the surroundings thereof.   
Johannesburg will benefit from green rooftop systems.  The citizens and environment will 
benefit from improved air quality, better insulated building, job creation, aesthetics, 
eliminating the heat island effect, stormwater management and economic growth, increased 
property values, sustainable city, secure and safe areas, promotion of health and decrease 
in stress, anxiety and depression as well as the conservation of indigenous plant species.  
The financial impact of the development of green rooftop systems is a concern.  However, 
there is a demand for green rooftop systems and therefore increases property value, thus 
developments are feasible regardless of the extra costs.  Despite water shortage, 
respondents would rather use alternative methods to solve the water shortage problem than 
not to develop green rooftop systems. 
To encourage the development of green rooftop systems in South Africa, and specifically 
Johannesburg, incentives may play a role.  Improved air quality, job creation and aesthetics 
are three elements that will encourage the development of green rooftop systems as well as 
being beneficial to Johannesburg.  Thus the three elements are regarded as the components 
that will encourage professionals and citizens to develop green rooftop systems in the 
Johannesburg area. 
9.5 RECOMMENDATIONS FOR FUTURE RESEARCH 
9.5.1  Recommendations for industry 
The lack of experience and knowledge regarding the construction of green rooftop systems 
in the industry is a concern and should be addressed.  This can be done in the form of 
seminars, courses and formal education. 
There is a demand for semi-intensive green rooftop systems in South Africa and the benefits 
to the environment and city is significant, thus the develop thereof will be beneficial and 
should be encouraged.   
107 
 
Due to water shortage problems in South Africa, it is recommended to use only indigenous 
vegetation, therefore require further research for the construction industry as such. 
Research regarding the building regulations and adjustments, in order to incorporate green 
rooftop systems in developments seems essential. 
9.5.2 Recommendations for further research 
Areas that require further research: 
 The different options to solve water shortage problems (recycled water from building, 
gathered storm water and indigenous vegetation) can be researched in order to 
determine how much each will cost and the feasibility of the system. 
 Further studies can be done in order to identify all the possible plants that have 
characteristics such as little maintenance, aesthetic, drought resistant, heat resistant, 
indigenous, wind resistant and hardy for roofs of the different cities in SA. 
 Market research need to be done in order to determine the exact value a green 
rooftop system add to the value of a building, as well as the breakeven point. 
 Research need to be done on the costs to change existing roofs to green rooftop 
systems in order to determine what the shortcomings are; is there any installation 
problems, leakage problems, drainage problems and/or vegetation problems.  
 Study need to be done in order to determine the cost per square meter, in South 
African currency, for the different types of green rooftop systems for new and existing 
buildings.     
 
108 
 
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113 
 
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121 
 
ANNEXURE A: QUESTIONNAIRE 
 
UNIVERSITY OF THE FREE STATE 
DEPARTMENT OF QUANTITY SURVEYING AND CONSTRUCTION MANAGEMENT 
 
Dear respondent, 
SURVEY ON GREEN ROOF GARDENS IN SOUTH AFRICA 
As a professional, your assistance with this research project would be highly 
appreciated.  The aim of the questionnaire is to obtain opinions on green rooftop 
gardens in South Africa.  The research is conducted as part of a MSc in Quantity 
Surveying study. 
Your participation through completion of the questionnaire will be highly appreciated 
and will contribute to the success of the research project. 
The information you supply will be regarded as highly confidential and will only be 
used for purposes of this study. 
My study leader, Dr. Benita Zulch, is assisting me.  If you wish to contact her, you can 
reach her at 051 401 3849. 
Thank you for your time in reading and completing the questionnaire within 2 weeks.  
Completed questionnaires should be emailed to rolien072@gmail.com.  
 
 
 
 
 
 
 
 
 
 
 
121 
 
GREEN ROOFTOP SYSTEMS: A SOUTH AFRICAN PERSPECTIVE 
The intention is to determine the current status of green rooftop systems in South 
Africa, how knowledgeable construction team members are regarding the subject, 
the possibilities for green roofs in South Africa and the implementation thereof.  
 
Please use X to mark the box that indicates your opinion regarding the level or 
answer most applicable to your environment.   
Personal data: 
Profession in construction industry: 
  
Engineer  
Architect  
Quantity Surveyor  
Project Manager  
Contractor  
Other (specify)  
 
Citizen of Johannesburg Metropolitan: 
 
Yes  
No  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
122 
 
SECTION 1: INTRODUCTION TO GREEN ROOFTOPS 
 
1.1 Are you familiar with the concept of green roof gardens/systems? 
Yes  
No  
 
1.2 Have you seen a green roof garden/system in South Africa? 
Yes  
No  
 
1.3 If your answer is yes in question 1.2, in which province/s? 
 
Gauteng  
Western Cape  
Kwa-Zulu Natal  
Free State  
Eastern Cape  
Northern Cape  
North West  
Limpopo  
Mpumalanga  
 
WHEN ANSWERING THIS QUESTIONNAIRE  
   
Please indicate your opinion related to the level of importance in respect of the 
listed statements, circling the appropriate number in each row.  Please answer 
all questions.  The scale is as follows:  
1          Not important  
2          Fairly important  
3          Important  
4          Very important  
5          Extremely important  
 
 
 
 
 
 
 
 
 
 
 
 
123 
 
1.4 Which type of green rooftop system would best be feasible for an average South 
African citizen?   
A: Extensive B: Semi-Intensive C: Intensive 
     
Vegetation: Sedums, moss, Vegetation: Perennials, Vegetation: Shrubs, trees, 
perennials. small shrubs, succulents, lawn. 
 lawn.  
Low plant diversity. Medium plant diversity. High plant diversity. 
Low maintenance. Medium maintenance. High maintenance. 
Low initial cost. Medium initial cost. High initial cost. 
No recreational space. Pleasant recreational space. Excellent recreational 
space. 
  
 
A: Extensive 1 2 3 4 5 
B: Semi-Intensive 1 2 3 4 5 
C: Intensive 1 2 3 4 5 
 
SECTION 2: EFFECTS OF GREEN ROOFTOPS 
 
2.1 Which factors will influence the development of a green rooftop building? 
 
(1 = strongly disagree, 5 = strongly agree) 
Green roofs provide insulation to a building 1 2 3 4 5 
that lessens the usage of energy. 
Life extension of waterproofing on roof. 1 2 3 4 5 
Sound insulation dampens the level of 1 2 3 4 5 
external noise. 
Absorb and retain rainwater, thus limiting 1 2 3 4 5 
the rundown water and overflowing streets. 
Minimizing heat island effect (more pleasant 1 2 3 4 5 
environmental air temperature). 
Creating habitats & ecological biodiversity. 1 2 3 4 5 
Creating recreational space. 1 2 3 4 5 
Aesthetically pleasing. 1 2 3 4 5 
Agriculture, cultivating food for the nation.   1 2 3 4 5 
Improving air quality. 1 2 3 4 5 
Secure and safe area. 1 2 3 4 5 
Privacy. 1 2 3 4 5 
Creating jobs in industry. 1 2 3 4 5 
Demand from consumer. 1 2 3 4 5 
Property value increases. 1 2 3 4 5 
Identity 1 2 3 4 5 
Memory 1 2 3 4 5 
Belonging 1 2 3 4 5 
124 
 
2.2 Johannesburg will benefit from the following elements? 
(1 = strongly disagree, 5 = strongly agree) 
Well insulated buildings with a better 1 2 3 4 5 
temperature regulation, which leads to 
saving energy/electricity. 
Life extension of waterproofing on roofs, 1 2 3 4 5 
thus less maintenance costs. 
Sound insulation, which dampens the level 1 2 3 4 5 
of external noise. 
Less overflowing of stormwater in the 1 2 3 4 5 
streets in heavy rainfall. 
Minimizing heat island effect (more pleasant 1 2 3 4 5 
environmental air temperature, especially in 
summer maximum temperature is lower). 
Creating habitats and ecological 1 2 3 4 5 
biodiversity. 
Creating recreational space. 1 2 3 4 5 
Aesthetically pleasing building environment. 1 2 3 4 5 
Agriculture, cultivating food for the 1 2 3 4 5 
immediate community.   
Improving air quality. 1 2 3 4 5 
Secure and safe areas. 1 2 3 4 5 
Privacy for individuals.  1 2 3 4 5 
Job creation. 1 2 3 4 5 
Economic growth. 1 2 3 4 5 
Increased property values 1 2 3 4 5 
 
2.3 Do you live or work within 1km of a green open park? 
Yes  
No  
 
2.4 Mark on scale from 1 to 5 where 1 is never and 5 regular, the level of utilizing that 
open space/park? 
(1 = never, 5 = regular) 
1 2 3 4 5 
 
2.5 Rate the reasons for not utilizing the open green spaces/parks. 
(1 = strongly disagree, 5 = strongly agree) 
Unsafe 1 2 3 4 5 
Crime 1 2 3 4 5 
Filthy and littered 1 2 3 4 5 
Lack of maintenance 1 2 3 4 5 
Lack of privacy 1 2 3 4 5 
  
 
125 
 
2.6 Is Johannesburg a healthy and sustainable city?  
(1 = strongly disagree, 5 = strongly agree) 
1 2 3 4 5 
 
2.7 From a health perspective, do green spaces in the city contribute to? 
(1 = strongly disagree, 5 = strongly agree) 
Decrease in personal stress. 1 2 3 4 5 
Improve worker productivity. 1 2 3 4 5 
Reduce patient recovery time. 1 2 3 4 5 
Reduce depression. 1 2 3 4 5 
Reduce anxiety.  1 2 3 4 5 
Promotes health. 1 2 3 4 5 
 
2.8 Considering the health benefits as per question 2.7, would you make it a priority to 
work and live in close proximity to green spaces? 
Yes  
No  
 
2.9 Which residence would you rather rent? 
 
A: Apartment in a building with no B: Apartment in a building with exclusive 
exclusive recreational space to offer, for green rooftop space to offer for R8 000.00 
R7 000.00 per month. per month. 
 
A  
B  
 
 
  SECTION 3: CONSTRUCTING GREEN ROOFTOPS 
 
3.1 Do you have any experience in the construction of a green rooftop system, either 
as part of your profession or personally? 
Yes  
No  
 
 
 
 
126 
 
3.2 Considering construction of green rooftop systems, rate the factors to take into 
consideration? 
(1 = not applicable, 5 = extremely important) 
Location and climate 1 2 3 4 5 
Weight loading 1 2 3 4 5 
Professional consultants 1 2 3 4 5 
Drainage 1 2 3 4 5 
Access to the roof 1 2 3 4 5 
Availability of the materials 1 2 3 4 5 
Specializing suppliers 1 2 3 4 5 
Water usage problems 1 2 3 4 5 
  
3.3 If water in South Africa is a problem, what will you do? 
 
(1 = strongly disagree, 5 = strongly agree) 
Ignore a green rooftop development. 1 2 3 4 5 
Choose a green rooftop system that 1 2 3 4 5 
survives on the seasonal rain of the location. 
(Extensive system, see question 1.6) 
Recycle water used by the building and re- 1 2 3 4 5 
use the water. 
Gather storm water in a tank to be utilized 1 2 3 4 5 
for the green rooftop. 
 
3.4 To what degree would the following concerns limit you from 
developing/encouraging a green rooftop system: 
 
1 = not at all, 5 = completely) 
Structural integrity 1 2 3 4 5 
Maintenance 1 2 3 4 5 
Vermin problem 1 2 3 4 5 
High cost 1 2 3 4 5 
 
3.5 How effective would the growth of green rooftops be in South Africa when 
implemented in the following ways? 
(1 = strongly disagree, 5 = strongly agree) 
Green rooftop systems are included in 1 2 3 4 5 
South Africa’s building regulations. 
Communication, negotiation and persuasion 1 2 3 4 5 
of implementation (e.g. seminars).  
Competitions and awards. 1 2 3 4 5 
Public buildings as ‘displays’ of potential 1 2 3 4 5 
green rooftop buildings (e.g. schools, 
hospitals). 
Municipal grants 1 2 3 4 5 
State legislation 1 2 3 4 5 
Incentives 1 2 3 4 5 
 
127 
 
SECTION 4: VEGETATION TO GREEN ROOFTOPS IN JOHANNESBURG 
 
4.1 What characteristics in the plants would you prefer in the green rooftop system? 
(1 = strongly disagree, 5 = strongly agree) 
Hardy 1 2 3 4 5 
Require little maintenance 1 2 3 4 5 
Aesthetically pleasing 1 2 3 4 5 
Draught resistant 1 2 3 4 5 
Heat resistant 1 2 3 4 5 
Wind resistant 1 2 3 4 5 
Indigenous 1 2 3 4 5 
  
4.2 Indicate the plants that are suitable for rooftop conditions, that you would 
consider planting on green rooftops? 
(1 = strongly disagree, 5 = strongly agree) 
Lemon 1 2 3 4 5 Drooping 1 2 3 4 5 
Thorn  agapanthus 
 
Pineapple 1 2 3 4 5 Slymstok 1 2 3 4 5 
Flower   
Porkbush 1 2 3 4 5 Snake 1 2 3 4 5 
 flower 
 
Soap 1 2 3 4 5 Meelplakkie 1 2 3 4 5 
Aloe  
 
Kranz 1 2 3 4 5 Doll's 1 2 3 4 5 
Aloe  powderpuff  
Klipsalie 1 2 3 4 5        
 
 
Thank you very much.  Your valuable time is most appreciated. 
128