-
UV-UFS
BLOEMFONTEIN
BlaUOTEEK • LIBRAR-Y J
urr DIE University Free State
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34300005157023
~.s _ Universiteit Vrystaat
TIMBIERaFRAME WALLS CONSTRUCTION AS
ALTERNATIVE TO MASONRY BRICK WAllS
CONSTRUCTION FOR RECONSTRUCTION AND
DEVIELOPMENT PROGRAMME HOUSES; AN
ANAL YT~C EFFECT~VENIESS OF TIMBER
By
MalInleoAdelina Malbesa
2000018842
supervlsor: M.S. Rarnabodu
A thesis submitted for fulfilling the requirements for the Master
programme in Quantity SUlD'Veying
At University of the Free State
Faculty of Natural and Agricultural Sciences
Department of Quantity Surveying and Construction Management
Bloemfontein
November 2013
rt 5 APR lOW
The thesis of Maneo Adelina Mabesa is approved by
Mr MS Ramabodu (supervisor)
ABSTRACT
The imbalance and diversities in the housing problem have to be addressed in South
Africa. Attention should be given to investigating the basic needs and means of those
who need shelter.
This document is a study on timber-frame wall construction as an alternative to
masonry brick-wall construction for the Reconstruction and Development Programme
(ROP) houses; an analytic effectiveness of timber.
A study was carried out comprising on-site and literature investigations in addition to
interviews with key persons such as engineers, contractors and the general public.
Although this study attempts to cover most of the factors influencing the use and
advantages of timber-frames, the purpose is to investigate timber-frame walling as a
possible replacement to traditional masonry brick walling on ROP houses. The
objective is to speed up housing delivery and to save money, as well as to analyse
the effectiveness of timber.
The investigation indicates that timber-frame material is as competitive as any other
conventional building material. A house built with timber is not a cabin or a temporary
building. It is a permanent structure which is as durable, effective and resilient as any
other accepted construction material and comes with a number of benefits.
KEYWORDS
South Africa, timber-frame wall, masonry wall, ROP, houses.
ACKNOWLEDGEMENTS
I thank all the people who helped me with my research. I am specifically thankful to
Messrs Baloyi and Thinyane for all the interest and support they gave me. They have
taught me technical issues, shared experiences, and overall they have taught me
values of construction industry. I also thank Professor J.J.P. Vester, for offering me
opportunity to write this research
II
DECLARATION
I, Maneo Adelina Mabesa, do hereby declare that the work contained in this thesis is
entirely my own work, except where otherwise stated and not been produced in any
manner or form before.
Maneo Adelina Mabesa_ -t_,~ _
Date November 2013
iii
TABLE OF CONTENTS Page No.
ABSTRACT
ACKNOWLEDGEMENTS ii
DECLARATION iii
CHAPTER 1
1 THE PROBLEM AND SETTING 1
1.1 INTRODUCTION 1
1.2 THE RESEARCH PROBLEM 2
1.2.1SUB PROBLEMS 2
1.3 THE HYPOTHESIS 3
1.4 THE LIMITATIONS 3
1.5 SCOPE 3
1.6 METHODOLOGY 4
1.7 THE AIM AND IMPORTANCE OF THE STUDY 4
1.8 THE ASSUMPTIONS 4
1.9 ABBREVIATIONS 4
2.0 CHAPTERS OUTLINE 5
CHAPTER 2 7
2 METHOD OF TIMBER-FRAME AND MASONRY WALL
CONSTRUCTION 7
2. 1 Introduction 7
2. 2 Masonry Brick Wall Construction System 8
2.2.1 Wall construction duration 11
2. 2.2 Material used in a brick wall system 11
2.2.2.1 Brick 11
2.2.2.2 Mortar 11
2.2.2.3 Damp Proof Course 12
2.3 Timber-frame Wall Construction System 12
2.3.1 Members of a frame wall system 13
2.3.1.1 Oriented Strand Board 14
2.3.1.2 Nutec panels 14
2.3.1.3 Gypsum board 14
iv
2.3.1.4 Aerolite 15
2.4 Timber-frame wall construction method and construction duration 16
2.4.1 Foundation 17
2.4.2 Floors 17
2.4.3 Structure 18
2.4.5 Openings in timber-frame wall 19
2.4.6 Construction of walls in the Republic of South Africa 20
2.4.7 Cladding 21
2.4.8 Insulation 22
2.4.9 Keeping external wall frames dry 23
2.4.10 Avoiding roof condensation 23
2.4.11 Heating, plumbing and electrics 24
2.4.12 Roofing 24
2.5 Wall construction duration 25
2.6 The advantages and disadvantages of brick and timber-frame wall building
systems 26
2.7 Timber-frame wall 27
2.8 Concrete brick wall 28
2.9 Conclusion 29
CHAPTER 3 30
3 TIMBER-FRAME BUILDINGS COMPARED TO CONVENTIONAL
BUILDINGS 30
3.1 Introduction 30
3.2 What are the differences? 31
3.3 Conclusion 35
CHAPTER 4 36
4 THE ADVANTAGES AND DISADVANTAGES OF TIMBER-FRAME
CONSTRUCTION 36
4.1 Introduction 36
4.2 Wood is good for the environment 36
4.3 Energy efficiency 37
4.4 Timber-frame is a renewable material 37
v
4.5 Seismic quality 38
4.6 Flexibility 38
4.7 Durability and Adaptability 39
4.8 Strength 40
4.9 Aesthetics quality 40
4.10 Acoustic Performance 41
4.11 Insulation 41
4.12 Less wastage of materials in timber-frame construction 42
4.13 Dry Construction 42
4.14 Renovations and Alterations 42
4.15 Life expectancy of timber-frame houses 43
4.16 Conclusion 44
CHAPTER 5 46
5 LOW INCOME HOUSING IN SOUTH AFRICA 46
5.1 Introduction 46
5.2 Housing as a human right and the South African Constitution 47
5.3 Reconstruction and Development Programme (ROP) 47
5.4 ROP housing allocation 48
5.5 Housing backlog 49
5.6 Building material for ROP houses 50
5.4 Conclusion 50
CHAPTER 6 52
6 COMPARATIVE COST ANALYSIS OF TIMBER-FRAME AND BRCIK WALL
CONSTRUCTION 52
6.1 Introduction 52
6.2 The comparison of masonry brick wall and timber-frame wall 53
6 .2 .1 The Cost of walls constructed with the masonry bricks and mortar
method 53
6.2.2 The cost of walls constructed with the timber-frame wall system 55
6.3 Cost comparison of construction of ROP house walls 56
6.4 Kothmann Case Study 56
6.4.1 Case study (timber structure is cheaper than steel structure) 56
6.5 Conclusion 59
vi
CHAPTER 7 61
7 THE RESEARCH METHODOLOGY 61
7.1 Introduction 61
7.2 Methodology 62
7.3 Qualitative research 62
7.4 Questionnaires 63
7.4.1 Questionnaires to the building professionals 64
7.4.2 Questionnaires to the general public 68
7.5 Interviews 69
7.6 Field Work 70
7.7 Conclusion 70
CHAPTER 8 72
8 FINDINGS 72
8.1 Introduction 72
8.2 Data collection procedure 72
8.3 Questionnaires to the building professionals 72
8.4 Questionnaires to the general public 75
8.5 Interviews to two contractors 77
8.6 Conclusion 78
CHAPTER 9 79
9 CONCLUSION AND RECOMMENDATION 79
9.1 Introduction 79
9.2 Conclusion 79
9.3 Recommendation 81
vii
LIST OF FIGURES I PICTURES
Figure 1: Figure 1: RDP brick wall house in Bohlokong 9
Figure 2: Construction of concrete block walls 10
Figure 3: Brick wall orientation called stretcher 10
Figure 4: Gypsum board on the inside walls 15
Figure 5: Aerolite 16
Figure 6: Suspended timber floor construction 18
Figure 7: The timber-frame external wall openings 20
Figure 8: Cladding on block wall house 22
Figure 9: Placing of aerolite 23
Figure 10: Timber roof trusses and rafters 25
Figure 11: Timber-frame house 28
Figure 12: Timber structure 39
Figure 13: Timber-frame house in Bethlehem 41
Figure 14: Questionnaires issued to professionals 65
Figure 15: Responses from professionals 67
Figure 16: A bar chart showing years of experience of the building professionals 67
Figure 17: Questionnaires issued to the general public 68
Figure 18: Responses from general public 68
Figure 19: A bar chart showing responses from professionals 75
Figure 20: General public responses 77
Figure 21: Timber-frame house 84
LIST OF TABLES
Table 1: The elements of timber-frame wall and sizes 19
Table 2: Permissible dimensions for timber-frame wall 21
Table 3: Advantages and disadvantages of timber-frame and brick wall building
systems 27
Table 4: Summary of some of advantages and potential problems of timber
construction 44
Table 5: Kothmann's findings 58
Table 6: Number of questionnaires sent to the professionals 64
Table 7: Categories of building professionals respondents 66
Table 8: Questionnaires handed out to the general public 68
Table 9: Categories of general public responded 69
VIII
Table 10: Responses from building professionals 74
Table 11: Responses from the general public 76
Appendix A 85
Appendix B 87
BIBLlLOGRAPHY 88
Appendix C 94
ix
CHAPTER 1
1 THE PROBLEM AND SETTING
1.1 INTRODUCTION
It has been reported that a fifth of the world's houses are built from earth materials
(Elizabeth & Adams, 2005:7). Nonetheless there have been two technologies widely
used for residential architecture throughout the world. One is traditional masonry such as
bricks, concrete blocks and stones, and the other one is lightweight construction, with
predominantly timber-frames. Each of these building techniques has its own unique set
of tradeoffs and to consider which method to use; their relative merits have to be
analysed and compared (Srinkley, 2005).
In South Africa, bricks and concrete blocks remain the primary materials for construction
of houses and are used extensively in buildings of all types, low income houses included.
This is because masonry has a lot of advantageous properties like acoustics, durability,
low maintenance, a strong structural frame, fire resistance and aesthetics (Pringle &
Sruce, 2011). With the South African government failing to deliver quality low income
houses in the specified time and budget, the Department of Human Settlements (RSA)
will have to undertake investigations in respect of alternative building technologies which
should have all the requisite standards for quality, norms and standards and while
facilitating rapid housing delivery. Thus, the idea of using timber-frames as an alternative
method of construction (unlike the usual brick and mortar) was triggered to promote a
better quality of structures, faster construction solutions and to discover new economic
developments.
A timber-frame house differs from a brick and mortar house only with regard to the walls,
as both types of houses have the same foundations, windows, doors and roofs.
Therefore emphasis will be placed on their respective walls to determine which type of
walls is the most viable, easily obtained, cost effective and durable. The selected method
of construction should be suitable for the construction of Reconstruction and
Development Programme (ROP) houses by being the quickest and most economical
method of erection.
"Timber-frame construction is a method of building that relies on a timber-frame as a
basic means of structural support. The panels are engineered in a factory environment
under strict quality control systems using computer aided design and manufacturing
machines. In the factory the weight-bearing structure of a building is made of heavy wood
panels instead of steel or concrete breeze blocks. Ironically, given its strength, timber-
frame construction is often referred to as lightweight construction" (Lund, [n.d.]: 13).
Timber-frame homes were re-introduced in South Africa as an alternative to conventional
brick homes in the early nineteen sixties (1963). One of the main reasons that timber-
framed homes have taken so long to become a norm in South Africa is a lack of suitable
indigenous timber, techniques and skills. However, milling and forestry techniques and
skills have improved over the years (Osborn, 2010). Even the South African National
Building Regulations accept' it as a high standard of construction method (SANS1200
and NBR - SANS 10400 - F: 2010).
While timber-frame houses are not common in South Africa, they have become a norm in
developed countries such as the United States of America and Canada. This alone
shows that there may be advantages to be gained from this type of construction.
1.2 THE RESEARCH PROBLEM
The goal of this study is to determine whether timber-frame walls can replace traditional
brick and mortar walls to improve quality, faster construction solutions, durability and cost
effectiveness.
Will timber-frame wall construction be a better alternative to brick wall construction in
South Africa? Can timber-frame wall construction be appropriate for RDP houses?
The housing problem in South Africa should be addressed. Government should find ways
of decreasing the shortage and slow delivery of low income houses by using the most
economic and efficient methods of construction.
1.2.1 SUB-PROBLEMS
Time and cost are two of the most important factors in the completion of any project. The
longer it takes to finish a certain project, the more expensive it becomes. The different
sub-problems are stated below:
1. What does the timber-frame construction method consist of and how can it be
helpful in the construction of RDP houses?
2
2. Is the timber-frame wall method quicker and more cost effective than masonry?
3. Is the timber-frame wall method of construction cheaper than the masonry
method of construction?
4. Is it easier to construct timber-frame wall constructions than masonry wall
constructions?
5. Which of the construction materials are more sustainable between brick and
timber-frame?
6. How does the construction of these methods differ? How do the timber-frame
walls compare with brick and mortar walls when it comes to durability?
1.3 THE HYPOTHESIS
Timber-frame construction is a cost effective and economic method of construction. It is
a better and quicker type of erection than brick and mortar. The use of timber-frame
construction is a possible alternative for house wall construction for the low income
groups of South Africans, as timber-frame erection is more energy efficient, cost
effective, and may provide home owners with affordable and durable houses.
1.4 THE LIMITATIONS
The purpose of the literature review is to identify the advantages and benefits of building
with timber to speed up the process of low income housing delivery. The study is limited
to masonry and timber-frame construction. Combining the literature investigations with
structured questionnaires and interviews makes the study more reliable and realistic.
1.5 SCOPE
The study will focus on timber-frame walls as an alternative to brick and mortar walls for
ROP houses. Timber-frame construction is not only durable and strong but also
lightweight, suited to all climate conditions, environmentally friendly and thermally
efficient. The selection of appropriate building materials is important to the quality and
sustainability of any structure.
Timber houses are as good as other conventional houses and they should be as
prevalent in the Republic of South Africa as houses built from bricks, blocks and
concrete. Timber-framed structures can be used for low income housing.
3
1.6 METHODOLOGY
Information gathered for this thesis comes from the following sources:
o A literature review regarding timber-frame construction by reviewing books,
timber manuals, guides, reports and information gathered from the internet;
o Engineering designs and building regulations' reviews (SANS1200 and NBR -
SANS 10400 - F: 2010) in order to assess compliance with standards;
o Interviews with contractors;
o A comparison of the cost of timber-frame wall and brick and mortar wall
construction;
o Site visits to examine where brick and mortar walls and timber-frame walls are
constructed in South Africa; and
o Distributing questionnaires to architects, contractors, quantity surveyors,
engineers and to the general public.
1.7 THE AIM AND IMPORTANCE OF THE STUDY
The principal aim of this research is to determine the cost effectiveness of timber frames
and outline the reasons why timber-frame houses should be as widely used in South
Africa as brick and mortar houses.
1.8 THE ASSUMPTIONS
The timber-frame method of construction may be environmentally friendly, and
ecologically and energy efficient. The overall aims of environmentally sustainable
developments are to reduce the use of energy, and to minimise adverse environmental
impacts.
1.9 ABBREVIATIONS
FSC Forest Stewardship Council
ILO International Labour Organisation
LCA Life Cycle Assessment
NHFC National Housing Finance Corporation
NTDC National Timber Development Council
OSB Oriented Strand Board
4
PER Product Energy Requirement
RDP Reconstruction and Development Programme
RSA Republic of South Africa
SAL MA South African Lumber Millers Association
SANS South African National Standards
SASFA South African Light Steel Frame Building Association
SATFBA South Africa Timber Frame Builder's Association
TBTN Tributyltin Napthnate
TFBA Timber Frame Builders Association
TRADA Timber Research and Development Association
UK United Kingdom
USA United State of America
2 CHAPTERS OUTLINE
In order to address the research problem as outlined above, this research report will be
divided into the following chapters:
CHAPTER 1 - THE PROBLEM AND SETTING
Chapter one introduces the reader to the research problem and gives a general idea of
what the study aims to accomplish.
CHAPTER 2 METHOD OF TIMBER-FRAME AND MASONRY WALLS
CONSTRUCTION
Chapter two investigates the advantages and disadvantages of brick and timber-frame
wall construction systems. Also to be discussed are different materials required for each
type of wall erection and the time it takes to construct each wall.
CHAPTER 3 - TIMBER-FRAME BUILDINGS COMPARED TO CONVENTIONAL
BUILDINGS
Chapter three compares timber-frame houses to conventional buildings such as brick
houses. The aim of this chapter is to focus on the advantages of timber-frame houses.
5
CHAPTER 4 - THE ADVANTAGES OF WOOD-FRAME CONSTRUCTION
Chapter four investigates timber-frame properties and advantages.
CHAPTER 5 - LOW INCOME HOUSING IN SOUTH AFRICA
Chapter five discusses South Africa's approach to low income housing, present statistics
of the housing backlog and building material for Reconstruction and Development
Programme houses (ROP).
CHAPTER 6 - COMPARATIVE COST ANALYSIS OF TIMBER-FRAME AND BRICK
WALLS CONSTRUCTION
In this chapter, the cost of constructing masonry brick walls and timber-frame walls is
compared to prove which method of construction is more cost effective.
CHAPTER 7 - THE RESEARCH METHODOLOGY
Chapter seven introduces the methodology used in the research. To discover more about
the problem and sub-problems, the literature study was supported by questionnaires,
interviews and field observations.
CHAPTER 8 - FINDINGS
The findings of the study are discussed in great length.
CHAPTER 9 - CONCLUSIONS AND RECOMMENDATIONS
In the last chapter the findings of this research report are revisited and a suitable
conclusion is drawn.
6
CHAPTER 2
2 METHOD OF TIMBER-FRAME AND MASONRY WALL CONSTRUCTION
2. 1 Introduction
There are typically two common wall systems being used in house construction, namely
timber-frame and masonry brick or block work. These methods are commonly used in the
building industry worldwide. While wood construction is not popular in South Africa,
timber houses are more prevalent in the developed world, where 70% of the population is
estimated to live in timber homes (Elizabeth & Adams, 2005: 10).
Walls and foundations play an important role in the stability of the structure, as well as in
the percentage of the building's total cost and construction time. Emphasis will be placed
on walls mainly because timber-frame and brickwork houses differ mainly with regards to
their walls. Other elements of a house structure such as foundations, floors, doors,
windows, ceilings and roofs are usually the same for the two construction methods.
In South Africa, masonry brickwork construction is the most preferable practice and
common solution for low income houses. This is because masonry brickwork has many
advantageous properties such as acoustics, durability, low maintenance and a strong
structural frame. The important one is durability. Bricks have been successfully used as a
building material for centuries. The numerous ancient structures and monuments built
with bricks that still exist in many parts of world such as the Pyramids and the large
Roman Aqueducts are a clear testament to its worthiness. Masonry brick walls are
structurally sound and have great compressive strength. The brick walls can, to a large
extent, hold up against the ravages of bad weather, and are generally resistant to fire,
maid and pests. The mortar used to bond brick or masonry blocks prevents water and
wind seepage into the building. These construction materials are incombustible and,
once in place, their surfaces offer little opportunity for maid growth or pest incursions.
Another advantage of a masonry building which is very important to the RDP houses is
its cost-effectiveness. Apart from the money saved in later maintenance work, the initial
construction costs are lower compared to other types of building (Rocky Mountain
Masonry Institute, 2002). Construction workers and materials are usually available
locally, and the construction can be carried out by a general contractor without too many
work delays. The use of material such as bricks and blocks can increase the thermal
mass of a building. The mass of a masonry brick walled building is also advantageous as
7
it acts as a barrier and prevents easy sound transmission. It reduces noise pollution and
helps in creating a quieter environment. This feature makes masonry construction ideal
for homes as well as public buildings where large numbers of people congregate.
Masonry brick walls also offer excellent thermal insulation. Their slow rate of heat
discharge keeps interiors warm in winter, and their high rate of heat absorption makes for
cool interiors in summer. Such energy-efficient buildings not only lower energy bills, but
the manufacture of the masonry materials used in their construction also requires lower
energy consumption (Davis, 2013). Another quality is aesthetics; houses built with brick
are mostly attractive and beautiful.
To replace the brick and block wall construction used on ROP houses, timber-frame wall
construction have to be more economical, cost effective and practical. This can be
achieved by reducing waste, reducing the amount of required materials, simplifying
assembly and increasing accuracy and the speed of construction. The materials and
construction techniques may be based on traditions or on more industrialised methods
using specialised skills, computerised manufacturing and design processes and
sophisticated equipment.
Timber-frame and masonry brickwork are acceptable building methods and comply with
the required building standards and regulations such as, the National Building
Regulations (NBR - SANS 10400 - F: 2010) and South African National Standards
(SANS 1200). These two methods of building wall systems will be compared and
discussed. Certain parameters such as durability, thermal performance and acoustic
performance will be taken into account.
2.2 Masonry Brick Wall Construction System
The most common use of bricks worldwide throughout time is in residential dwellings, as
shown in Figure 1 (an example of an ROP brick wall house). The shape and size of
bricks can vary considerably depending on the quality of the clay and the manufacturing
tradition. Similarly the mortars used depend on its strength. The materials used in mortar
mixes are sand, water, and one or more bonding agents such as mud, clay, or cement,
depending on local availability. The proportion of bonding agents to sand determines the
compressive and bonding strength of the mortar (D'Ayal, 2004).
8
Figure 1: ROP brick wall house in Bohlokong (own information).
Bricks are stacked on top of one another with mortar between them to bind them together
and to hold them in place as shown in Figure 2. The bricks can be laid in different
orientations such as stretcher (as shown in Figure 3), soldier, header, rowlock stretcher,
and sailor. The brick orientations will not be discussed in detail in this paper. A damp-
proof course is placed on top of foundation walls to prevent moisture from ascending into
the building from the foundation. Openings for doors and windows are created by leaving
openings in the walls. There are no channels for services left in walls and such channels
must be created using a grinder or hammer and chisel (Davis, 2013).
9
Figure 2: A picture illustrates construction of concrete block walls and how the blocks
were being stacked on top of one another, Maliele, Lesotho (own Information).
Figure 3: A picture illustrates orientation of the bricks called stretcher, Maliele, Lesotho
(own Information).
Brick force can be placed between the layers of brick to increase the strength and load
carrying capabilities. The more brick force used, the stronger the wall will be. Brick force
is normally placed in every third to fourth layer, but more or less can be used, depending
10
on the purpose of the wall and the required strength. For aesthetic and smooth finishes,
the external and internal walls may be plastered and painted.
2.2.1 Wall construction duration
A study was conducted on a construction site in Bohlokong, Bethlehem, where an RDP
house of 6.25m x 2.55m high double skinned brick wall was constructed. It took a skilled
bricklayer and a labourer roughly nine and half hours to construct the brick wall that
consisted of 1754 bricks.
2.2.2 Material used in a brick wall system
A house cannot be built without the fundamental knowledge of building materials and
construction (Stulz & Mukerji, 1993). Therefore material that makes up the brick wall will
be explained thoroughly. The properties or characteristics of different materials must
match the purpose of the structure. Properties include: brittleness, ductility, hardness,
plasticity, resistance to heat, resistance to water, compression and tensile strength (Stulz
& Mukerji, 1993).
2.2.2.1 Brick
A brick is a block, or a single unit of a ceramic material used in masonry construction.
Bricks are stacked together, or laid as brickwork using various kinds of mortar to hold the
bricks together and make a permanent structure. They are typically produced in common
or standard sizes in bulk quantities (Pandey, [n.d.]).They have been regarded as one of
the longest lasting and strongest building materials used throughout history. Their sizes
have varied over the centuries but have always been similar to present-day sizes
(D'Ayal, 2004). Some sizes were developed to meet specific designs, production or
construction needs. For example, larger bricks were developed to increase the
bricklaying economy, while thinner bricks help to conserve resources.
2.2.2.2 Mortar
Mortar is a workable paste used to bind construction blocks together and fill the gaps
between them. Mortar binds bricks and blocks together to give strength and stability to a
wall. The blocks may be stone, brick or concrete blocks. Mortar becomes hard when it
sets, resulting in a rigid aggregate structure. Modern mortars are typically made from a
11
mixture of sand, a binder such as cement or lime and water (Stulz & Mukerji, 1993).
Mortar joints to brickwork shall be not less than 5 mm or more than 10 mm thick and
descriptions of brickwork, unless otherwise specified, shall be deemed to include for
raking out joints whilst the mortar is soft to form an adequate key for plaster or mortar
backing (Mishra, 2012).
2.2.2.3 Damp Proof Course
A damp proof course (OPC) is a barrier of impervious material built into a wall or pier to
prevent moisture from moving to any part of the building. A damp-proof membrane
(OPM) performs a similar function for a solid floor. The OPC is built into the base wall
brickwork. It bridges brick skins and/or the brick and pier. OPC is used to stop dampness
in buildings (Burchell & Sunter, 1987:27).
The OPC is laid into the brick wall approximately two courses (two bricks) below the
lowest brick member, typically the bearer.
2.3 Timber-frame Wall Construction System
The use of timber-framed load-bearing walls and partitions is the most essential
difference between timber-frame and brick or block construction. The timber-framed load-
bearing walls are designed by the structural engineer to transmit the entire vertical and
dead load safely through to the foundations. The walls should be designed as to resist
racking and overturning loads which result from wind pressure and seismic shock. The
load-bearing walls combined with internal lining, insulation and external claddings should
be structurally sound, weatherproof and durable with thermal, acoustic and fire-resistant
properties (Burchell & Sunter, 1987:17). Timber-frame construction may be an alternative
wall construction method to brick and mortar. The timber-frame wall construction can be
erected faster than brick and mortar.
Timber-frame house construction can be erected by different methods. The most
common are:
e Platform-frame construction is the most common technique which is used mostly
in Canada, the United States of America (USA) and the United Kingdom (UK). It
can be explained as structural timber, with stud panels replacing the internal
partitions and inner leaf of the external walls (Burchell, 1984: 3). In platform
framing, each floor is built separately, one on top of another, and then the roof is
added on the top. Platform-frame offers infinite flexibility to the designer and
12
provides the builder and prefabricator with the opportunity to vary the size and
degree of factory contents in components to suit their particular requirements.
While there are some variations in material specifications, the main difference
between competing platform-frame 'systems' is in the type of component and how
far down the way towards a fully factory finished unit the manufacturer has gone
(Burchell, 1984: 4).
o Balloon-frame construction is a form of construction where the external timber-
frame extends from sole-plate level to eaves. The external panels having been
erected, the roof trusses are placed in position and the floor joist inserted on a
waist-band let into the studs of the external panels. Internal panels are put up
after the roof is in position. Long lengths of timbers are required. This type of
framing is not often used because it is difficult to transport large pieces of timber-
frames (Bellaloggia, 2009).
o Post and beam construction is a form of construction where large-section timber
beams are supported on large-section timber posts. Post and beam construction
is essentially a structural grid of beams supported on posts usually on a regular
spacing of between 2 and 5 meters which is an economical distance for spanning
secondary roof and floor members of solid timber. The external infill panels and
internal partition panels are usually identical to those used in platform-frame
construction, in order to achieve the necessary standards of acoustic and thermal
insulation and also to provide the necessary standards of wind and impact
resistance (Burchell & Sunter, 1987: 4).
o A volumetric housing unit is a form of a construction that is manufactured off site,
in the factory. The completed box is then transported to the prepared site (Lund,
[n.d.]: 14).
2.3.1 Members of a frame wall system
Many building materials are required to make up a timber-frame wall. The panels of solid
timbers are sheathed in or cladded with OSB (Oriented Strand Board) and gypsum
boards on the inside while on the outside are nutec panels and aerolite. All these
materials give the panel strength and durability.
13
2.3.1.1 Oriented Strand Board
OSB boards are made up of strands of wood which are layered and mixed with wax in a
specific orientation (Arnold, 1986: 6). The mixture of splinters, wax and waterproofing are
formed into large continuous mats. These mats are pressed under extreme pressure and
under high temperature into layers. The OSB boards are very versatile and reliable. The
boards are impact resistant, and have very good thermal and acoustic properties and
performance. They are moisture resistant and environmentally appropriate (Domone,
2001: 12).
2.3.1.2 Nutec panels
Nutec panels work as external cladding and are suitable for a wide range of internal and
external wall applications throughout the market. Nutec building planks are light-weight
and can be supported by light-weight metal galvanised steel frames or light timber
structures.They are offered in different sheets (Nutec, 2012).
2.3.1.3 Gypsum board
Gypsum board, also known as dry wall as shown in Figure 4, is made from a paper liner
that is wrapped around an inner core made of gypsum plaster. The gypsum used in the
inside is mixed with a few additives to increase the fire resistance and lower the water
absorption. The most commonly used additives include fibreglass, plasticiser, foaming
agent and potash. The wet gypsum is placed between two layers of heavy paper and
then dried in a drying chamber. When it comes out of the chamber it is strong enough to
be used as a building material. The 1200mm x 2400mm gypsum board is the most
common size. There are also other sizes which are seldom used. The thickness used for
walling is 12.5mm (Gypsum Association, 2012).
Two edge treatments are used most frequently: tapered edge where the end is a bit
smaller than the middle of the board to ensure that joining materials be flush with the
board, and straight edge, where the inside and the middle of the board are the same
size. Because the gypsum contains water of crystallisation it has very good fire
resistance. As the board receives heat the water is vaporized and retards heat transfer.
As a result, the room will not exceed boiling point. If the wall has more than one paper at
a side it is even more fire resistance. The board is not waterproof and therefore it should
be used only internally. The product is a high-grade material with mineral wool as the
14
main raw material. It has undergone the processes of burdening, forming, drying, cutting,
tendon-making and surface finishing (Gypsum Association, 2012).
Figure 4: The picture shows Gypsum board on the inside walls, Bokonq,
Information).
There are also two most used edge treatments: tapered edge where the end is a bit
smaller than the middle of the board to ensure that joining materials may be flush with
the board and straight edge where the inside and the middle of the board are the same
size. Because the gypsum contains water of crystallisation it has very good fire
resistance. As the board receives heat the water is vaporized and retards the heat
transfer. As a result, the room will not exceed boiling point. If the wall has more than one
paper at a side it is even more fire resistance. The board is not waterproof and therefore
it should be used only internally. The product is a high-grade material with mineral wool
as the main raw material. It has undergone the processes of burdening, forming, drying,
cutting, tendon-making and surface finishing (Gypsum Association, 2012).
2.3.1.4 Aerolite
Aerolite is a thick pink, high quality glass wool thermal and acoustic insulation that is
bonded with an inert, thermosetting resin. The strong, resilient, flexible blanket is
supplied in compression packed rolls as illustrated in Figure 5 below that are easy to cut
15
and install. It is made out of 50% recycled products such as broken glass and window
panels. It forms an efficient thermo barrier that reduces heat up to 5°C in the summer,
and reduces heat loss up to 87%. Aerolite can easily be installed even in hard to reach
places. Because it is made of glass, it is fire resistant and cannot burn (Aeropink, 2012).
Aerolite insulation is manufactured from pure spun glass bonded with an inert thermo-
setting resin to form a strong, easy-to-handle blanket.
Figure 5: Think pink aerolite with class 1 fire index rating. It is manufactured according to
ISO 9001 :2000 and is SABS tested and approved.
2.4 Timber-frame wall construction method and construction duration
The construction of a timber- frame wall is a rapid, clean, dry operation. The timbers can
be cut and assembled with simple hand or power operated tools and once the wall is
raised into position and fixed, it can be ready to receive wall finishes. A timber-frame wall
has adequate stability and strength to support the floors and roofs of small buildings,
such as houses. Covered with wall finishes it has sufficient resistance to damage by fire,
good thermal insulating properties and reasonable durability, providing it is sensibly
constructed and protected from decay (Barry, 1988: 105).
A standard method is used for wall frames. This is used for:
External walls;
Separating walls formed of double frames, one for each dwelling;
Ground floor partitions that carry floor joists in a two storey dwelling; and
Internal wind bracing partitions (NBA, 1989: 17).
16
In contrast with a brick and mortar house, a timber-frame house is built by carpenters.
With the exception of the foundations, all the structural elements above ground level are
built using timber.
2.4.1 Foundation
According to Burchell (1984: 11), the first step in the construction of any house is for the
architect to prepare detailed building plans. Once these plans have been drafted and
passed, the foundations can be laid. Whichever method of building is used, attention
needs to be paid to the foundations and groundwork. There are four main kinds of
foundations to consider: strip foundation, raft foundation, pad foundation and pile
foundation. Strip and pad foundations are the most common types, while raft and piled
foundations are reinforced foundations usually used for more difficult sites.
A typical modern wood-frame house consists of a reinforced concrete strip-footing
foundation, just like the masonry brick and mortar ROP house. The floor is constructed in
such a way that it resists the passage of moisture from the ground to the interior of the
building. In a timber-frame house floor, above the sole plate level all connections are
timber to timber and no joist are supported on masonry. This should be in place prior to
the erection of the walls (Barry, 1988: 10).
2.4.2 Floors
The design and construction of the ground floor will mostly be determined by the ground
conditions. There are three main types of ground floor construction: traditional ground
supported concrete floors, suspended timber floors as illustrated in Figure 6, and pre-
cast concrete beam and block floors. In the case of difficult ground conditions, such as
slopes and clay soil, a suspended floor will be required. Timber is used here, as wood is
very versatile and allows for some ground movement. Suspended timber floor
construction is also the preferred choice for first floors. Flooring on both ground and first
floors may be part of the first fix carpentry, or one may prefer to sereed the ground floor.
If walls are dry-lined, it is important to let the sereed dry out first. Screed provides a
smooth surface on to which carpets, tiles and timber floor covering is laid. Screed is also
the best covering for under-floor heating, which should be planned well in advance of
floor construction. Tongued and grooved boarding, clipboard or plywood may be used
and these materials are applied as in other housing (NBA, 1989: 6).
17
Figure 6: Suspended timber floor construction on a second floor of the house in Bokong,
Lesotho (own Information).
2.4.3 Structure
The National Building Agency (NBA) method of building uses floor joists and trussed
rafters which are carried on wall frames. These are floor to ceiling level panels, not more
than 3.6m long so that they can be handled by man. They are made up of uniformly
spaced vertical members, known as studs. The standard spacing of the studs is usually
at 600mm, 400mm and 300mm centre. This is to ensure that the joints will occur at the
centre. Unless specified otherwise all the joints are made with nails set out at 600mm
centres.
The same type of frame should be used for external walls, for internal partitions carrying
floor joists and for separating walls between dwellings. The latter are made of double
frames with, one for each house (NBA, 1989: 18). Wall panels may be assembled with a
single top rail or alternatively a top plate may be incorporated as a binder. This acts as a
beam between the studs and allows joints and rafters to be located (BurchelI & Sunter,
1987:17).
External walls should be sheathed outside throughout, with OSB boards or other suitable
sheeting. This stiffens the structure against wind loads. In some cases, sheathing is used
to stiffen certain internal partitions. Openings which are formed with lintels are usually
made up of double joist material. With large openings or with heavy loads from the upper
18
floors and roofs, hardwood lintels are needed. Lintels are carried on extra studs, known
as cripple studs (Burchell & Sunter, 1987: 17).
Table 1: The table below shows the elements of timber-frame wall and sizes
Top & Bottom Plate - 140 x 38mm treated
Studs - 140 x 38mm treated at 600mm centres
Lintels - 220 x 45mm treated or as required by
design
Sheathing - 9.5mm OSB (factory fitted)
Breather Membrane - Glidevale Protect tf200 thermo (factory
fitted)
Head plate - 140 x 38mm treated
Packer Head plate - 140 x 14mm treated as required by design
Insulation - 140mm glass fibre (between studs)
Plasterboard - 12.7mm Plain plasterboard (taper edged)
on
vapour barrier
U Value - 0.23 W/m2K (standard - options available)
(NBA, 1989: 5).
All framing should be designed so that simple butt joists and nails are used for assembly.
Accuracy in the work is fundamental. Lintels are carried on extra studs, known as cripple
studs and nailing schedules should be followed but no special skill in carpentry is
required (NBA, 1982: 5).
2.4.5 Openings in timber-frame wall
Openings can be of any width up to a maximum of 2.1 m. The heads of all main openings
should be 2.1 m above floor level. In all frames, any opening must be at least 300mm
away from the ends of the frame, and from any other opening.
Small openings, which can be fitted between studs, are simply framed up, using the
standard section. Large openings require lintels. This includes openings in internal
partitions carrying upper floor joists. Lintels are always fitted between studs, directly
under the head plate of the wall frame. They are carried on extra studs, known as cripple
studs (Allen & lano, 2004:16).
19
Figure 7: The timber-frame external wall openings were fitted with windows at Bokong in
Lesotho (own Information).
2.4.6 Construction of walls in the Republic of South Africa
Any wall used as a structural external or internal wall, non-structural internal wall,
external wall panel, parapet wall, balustrade wall, free standing wall or retaining wall shall
comply with rules KK3 to KK17, noted under Section K of SANS 10400: 2010 as the case
may be. Where such a wall is non-structural and a timber-frame, it shall be constructed in
accordance with SANS 082. The height and unsupported length of such wall shall not
exceed the limits given in Table 2 below (SANS 082: 16).
20
Table 2: Permissible dimensions for timber-frame wall
Wall type IStud size Stud ,Support Supported IMaximum Maximum
mm spacing ed both one end height m height, m
mm ends
Structural 114 x 38 400 4.8 2.4 6.0 4.0
114 x 38 600 4.0 2.0 6.0 3.0
76 x 38 450 3.6 1.8 6.0 3.0
Non 114 x 38 600 4.8 3.0 I - 4.0
Structural 176 x 38 600 4.2 2.4 3.0
Maximum height means height to wall plate of highest floor or height to top of a gable, if
there is a gable (Freeman, 1985: 151).
Where any wall is of timber-frame construction, the height and unsupported length shall
not exceed the values given in Table 2.
2.4.7Cladding
The OSB (Oriented Strand Board) boards can then be fixed onto the wood-frame as
cladding for interior walls. Cladding is usually used for exterior finishes, waterproofing the
walls and providing the necessary fire resistance. Exterior finishes are not structural as
they do not support the floors and the roofs. In some cases, the nutec panels (flat
sheets), gypsum boards and stones as illustrated in Figure 8 are used as cladding for
exterior walls (Smit, 2003: 16). While gypsum boards can work both as external and
internal cladding, it can also provide decorative finishes for the walls and strong surfaces
capable of withstanding normal wear and tear. The gypsum board is used as internal
lining to walls and ceilings. It also requires being fire resistant and preventing the
transmission of sound.
21
Figure 8: The concrete block wall house in Matsoku, Lesotho was cladded with masonry
stone (own information).
2.4.8 Insulation
Thermal insulation as required by the building regulations is easily achieved in timber-
frame construction by placing the insulation in the walls or ceilings cavities as shown in
Figure 9. The spaces between the studs are covered with aerolite insulation (as
mentioned on page 17) which is face-fixed into the face of the studs (Arnold, 1995:
22).Thermal insulation is used to prevent heat loss, thus conserving energy to provide
heat within the house. The ceiling insulation construction for timber-frame construction is
exactly the same as for masonry construction.
22
Figure 9: The diagram illustrates placing of aerolite in the ceiling of a house in
Mohlanapeng, Lesotho (own information).
2.4.9 Keeping external wall frames dry
Two steps are taken to keep external wall frames dry.
First, a polyethylene sheet is fixed to the inside face, or aluminium foil-backed
plasterboard is used to prevent condensation within the walling. Second, special building
paper known as breather paper, is fixed to the outside face of the plywood sheathing.
This prevents any rainwater that may get behind the cladding from wetting the wall
panels, but it is not impervlous to water vapour, and as a result, it will not trap vapour and
cause condensation. Both the vapour barrier on the inside and the breather paper on the
outside have an important function and they must therefore be carefully fixed on site to
give complete protection, and any damage must be repaired (Roy, 2004).
2.4.10 Avoiding roof condensation
With good insulation of ceilings, roof spaces get cold in winter. This increases the risk of
condensation on the sharking felt. Because of this, good ventilation of the roof space is
needed with cross ventilation usually being used. The total free area is not to be less
than 1/300th of the ceiling area. Part of this area should be provided in the form of ridge
23
ventilators in the cases of shelter sites and narrow fronted houses. To ensure that roof
insulation continues right up to the eaves but does not obstruct the airflow from any
eaves ventilators is crucial (NBA, 1982: 5).
2.4.11 Heating, plumbing and electrics
Accurate dimensions must be given on the drawings to locate service entry positions like
electrical, plumbing and heating. Plumbers and electricians should not be allowed to cut
notches or drill as they please. The rules that are set out in manuals should be followed.
These services are easily installed within the walls, in the open space above ceilings,
within the floor structure, and in the space between the ground floor and the first floor. As
with other types of housing, no wiring or pipe work should go into separating walls
between dwellings. The holes made would be liable to let noise through (NBA, 1982: 6).
2.4.12 Roofing
Finally the trussed rafters as illustrated in Figure 10 are erected and fixed, together with
their bracing and verge ladders. Felt and battens are then laid over the trussed rafters.
This should be laid as soon as practicable in order to protect the timber, following which
the upper floor decking can be laid, if not already fixed. Temporary bracing can then be
removed. The roof structure typically consists of prefabricated trusses, which are covered
with sheathing and roof tiles (Osborn, 2010: 10).
24
Figure 10: The photo demonstrates timber roof trusses and rafters, Matsoku, Lesotho
(own Information).
The following measures increase the longevity of wood-frame wall structures:
• Use a roof overhang;
• Use properly installed flashing;
• Avoid exposing large beams and columns to the elements;
• Protect band boards and underlying sheathing and siding;
• Provide adequate gaps between deck board and between ledgers and walls;
• Provide drainage and avoid creating spaces where water can collect;
• Provide ventilation where appropriate; and
• Select wood that will last (ThaIIon, 2000:4).
2.5 Wall construction duration
According to Ochshom (2010) an average timber-frame building can be erected and
completed in a third of the time it takes to build the same structure in brick and mortar. It
can be weather-proofed in five days or less. This means that tradesmen such as
plumbers and electricians can get to work on the inside of the house from virtually the
outset. The house may be occupied within six to eight weeks. That is an incredible
saving in time, which can mean big savings in labour costs, rental and storage costs as
well as a faster return on investment.
25
While a brick and mortar house is built by bricklayers, who are easy to come by, a
timber-frame house is built by carpenters. With the exception of the chimney, all the
structural elements above ground level are built using timber. The timber panels can be
prepared off site, at a factory. This greatly reduces the work done on site and it usually
takes fewer weeks as opposed to several weeks needed to build a masonry
superstructure (Scot, 2007: 46). The erection time for a big timber-frame house was also
witnessed on the television program "Extreme Makeover: Home edition" in which a house
was built in seven days.
2.6 The advantages and disadvantages of brick and timber-frame wall building
systems
Certain parameters need to be considered when constructing walls and these include:
o Structural strength: resistance to all likely loading, e.g. compression, tension,
flexion and impact (Hodges & Simitses, 2005: 5).
o Structural stability: the ability of a structural assembly to carry loads and forces
and determine how stable it will be over time (Hodges & Simitses, 2005: 5).
o Special requirements or in-service performance: resistance to seismic design,
vibration or cyclical loads, accidental loads, door slamming forces, attachment of
fitting, condensation and fire (Arnold, 1995: 16).
o Thermal performance: the result of the process through which the design, layout,
orientation and construction materials of the building modify the prevailing
outdoor climate to create an indoor climate (Seeker & Wang, 2011).
o Acoustic performance: good sound insulation by walls and floors whereby the
noise transmitted from both outside and inside the building can be controlled
(Smit, 2003: 22).
o Water resistance and damp-proofing: the state when no dampness is allowed to
penetrate on the inside of the external walls of a building for human habitation
under normal weather conditions, while the damp proofing elements should
comply with standards (Scot, 2007: 46).
o Durability: a period for which the specific material or structure fulfils its intended
function satisfactory when subjected to normal use, assuming reasonable
maintenance at regular intervals (Smith, 2008).
A comparison of advantages and disadvantages among the two systems is shown in
Table 3.
26
Table 3: Advantages and disadvantages of timber-frame and brick wall building systems
. II ~~Y~nt~9g§ ·11~~=j§~=~h='~=)1=~~=g§========~==~
• NI~~ium r\~~i~t;mc~ • Increas~d vari~ty of
to m~tur~1 h~~~rds components, .
• !"ljgh C(>rJstrJ.J(~tio.n ~qyipm~nt and
speed skills
, Med.i.um innov~tiv.e • lntermedlate level
d(!~jgn .~nd of ,ac~essibility Qf
com;'tl'u~tiol1 information fQr
teChl1igy(!s design, eenstructien
and maintenance
o COJT1PY!~ory uSe Qf
VItalI finishin9
f) Pos~ibilities of
. Insects and
fun.9i attac~s.
o Reduced number o High quantities
of materials and of the same
components material needed
o Materials could o It needs wall
be manufactured finishing to
in situ perform well
~6lffil~~ o . High thermal o Needs support and
capacities centring during
~ (common in construction
hot arid climates (verticality
o Medium to' lI1igh problems may
resistance to cause the failure
dampness of structure)
o MediLlm
construction
sPeed
o Accessible
Information for
design,
construction
and maintenance
(Ballerino, 2002).
2.7 Timber-frame wall
Timber-frame is probably one of the most commonly used materials for houses in the
developed world. The timber frame panels are manufactured off-site, usually in a factory
in a quality controlled environment, then loaded onto a truck, delivered to site and built
within a matter of days. The structural members of the panels are solid timber and the
27
outside of the frame is sheathed in OSB (Orientated Strand Board). This gives the panel
enormous strength and durability. Timber-frame construction is a very fast way of
building, which also makes it safer, less wasteful and very cost-effective (Arnold, 1986:
6). Timber-frame wall construction is erected by carpenters. Some negative aspects with
timber construction remain, however, including:
• Maintenance and treatment are required.
• Deforestation on a large scale causes environmental problems.
• Storage needs to be covered.
• Sensitivity to fires and biological agents such as fungus and insects (Bellaloggia,
2009).
Figure 11: Timber-frame house (TFBA, 2011).
2.8 Concrete brick wall
Concrete brick wall can be hollow or massive with mortar or interlocked as a dry-stack
masonry system. The masonry could be a non-reinforced or reinforced load-bearing wall,
depending on local conditions and standards. Construction could achieve efficiency if
well supervised and performed. The mortar can be traditional Portland cement or cement
mixed with lime and/or rice husk ash. The preferred mix is that one which complies with
SANS 50413-1. It must be soft and plastic so that it spreads easily and makes good
contact without becoming too strong (D'Ayal, 2004). Masonry brick walls are constructed
by bricklayers, and their negative elements include:
28
• Long term shrinkage of units placing wall under tension thereby increasing
cracking.
e Mixing of mortar must be done under control to obtain good results or cracks may
appear.
• Necessary to plaster and paint with waterproof painting.
• Requires on-site supervision.
e Methods of jointing must be controlled (Stulz & Mukerji, 1993).
2.9 Conclusion
The methods and materials used for the construction of this alternative wall construction
system obviously differ from the brick and mortar wall system. The materials used to
make up a brick wall are bricks, mortar and damp-proofing whereas the materials needed
for timber-frame walls are oriented strand board, nutec panels, gypsum board and
aerolite. This shows that timber-frame walls require more materials than masonry, which
needs only four items. The timber-frame panels can be manufactured off site which can
be quick and save erection time. With masonry brick and block wall construction, all the
hard work is done on site. The primary elements that are essential for a house to stand,
such as the foundation, floors, superstructure and roof are briefly discussed and the
requirements by the South African National Building Association are emphasised. This
shows that timber-frame and masonry brick construction differs only with regards to the
construction of walls.
Research has shown that it takes a shorter time to build timber-frame walls than masonry
brick or block walls. Timber-frame walls can be erected quicker and easier than the
traditional brick and mortar method, and this clearly proves the hypothesis that timber-
frame walls are constructed quicker and more easily than the traditional brick and mortar
method. For this reason, timber-frame walls are appropriate for ROP houses.
Timber-frame is also a lighter form of construction which may be of great benefit to the
foundations, especially where soil conditions are poor. The timber-frame wall technique
can be used in ROP houses because it can speed up the housing delivery processes.
29
CHAPTER 3
3 TIMBER-FRAME BUILDINGS COMPARED TO CONVENTIONAL BUILDINGS
3.1 Introduction
Timber-frame construction is now becoming acceptable as a conventional method of
building. Timber is both a trustworthy, traditional building material and one which is
suitable for the application of advanced engineering and production techniques aimed at
greater economy in the field of industrialised house building. In this chapter a timber-
frame house is compared to a conventional building such as a brick house to prove the
worthiness of the timber-frame house, to show that it can be durable, sustainable and as
good as a brick and mortar houses, if not more.
According to (Brinkley, 2011), the key difference between masonry-built and timber-
frame homes is the material used to build the load-bearing walls. In fact, a masonry
house is constructed by bricklayers, building up both internal and external walls. The
insulation inside the cavity between the two leaves of the external walls is fixed as the
construction continues. The doors and windows can also be installed as the process
continues. The construction of the external walls may stop at the first level to allow the
carpenters to place the floor joist, though sometimes the floor is pre-cast concrete,
craned into site. The bricklayers return to build up to roof level whilst the carpenters
return to build the roof. If the design includes gable walls, the bricklayers return for a third
time to complete the wall-building process.
In contrast, a timber-frame house is built by carpenters. With the exception of the
chimney, all the structural elements above ground level are built using timber. The timber
panels can be prepared off site, at a factory. This greatly reduces the work done on site
and it usually takes only a few weeks as opposed to several weeks needed to build a
masonry superstructure. The panels often have the windows and doors already in place.
Some methods supply fully finished walls and roofs, but the typical timber-frame house
has open panels; a semi-finished state that has to be insulated and cabled on site before
the plasterers cover the inner walls with a wall-lining board (Scat, 2007: 48).
30
3.2 What are the differences?
In South Africa, almost all new houses have a foundation built out of concrete and a roof
of timber. Thus, homes are, to some extent, both masonry and timber-frame.
Nevertheless, there are obvious differences between conventional construction and
timber-frame construction. These are the following:
a The main difference between the two types of construction is how the loads of the
house are held. With timber-frame, the frame itself supports the weight of the
house, while with brick and block; both the outer brick and the inner block take
the weight. The external walls of a conventional house are normally 230 mm
thick resting on concrete foundations. The external footings are 600mm x 200mm.
The internal walls are at least 115mm thick and their footings are 400mm x
200mm high. The internal walls and floors also vary in construction. With timber-
frame, dividing walls are plasterboard stud partitions, and floors are typically of
timber (although ground floors can be concrete). With brick and block, dividing
walls are usually solid block, and the floors are typically of solid beam and block
construction (Wagner, 2005: 23).
D In timber-frame houses, light weight timber frames form the skeleton for the
external and internal walls. This skeleton is erected on the substructure; that is,
the foundations for the external walls, and either a cement slab or timber
suspended floor for internal walls. The roof is supported on and anchored to the
external wall framing (NTDC, 2001).
D Window and door frames are mounted in the external frame before cladding with
a single leaf of non-load bearing brickwork or other acceptable cladding materials.
Cladding materials can also be stone, cement render, tiled hanging, wood
cladding, and composition board and plastic. Internal walls are cladded with
gypsum board, timber or any other approved and acceptable cladding material
(Lubber, 1986: 23). Windows in timber-frame houses are fixed on the inner
timber-frame, rather than to the brick outer skin, which results in a deeper
external sill. This feature helps to distinguish between the two types of
construction from the outside.
a According to ThaIIon (2000: 25), with timber-frame, only dry-lined plasterboard
may be used for the walls and the ceilings, while with brick and block, wet plaster
31
may also be used. With dry-lined plasterboard, wallpaper may be put up
immediately, whereas with wet plaster the waiting period is six months. Dry-lined
plasterboard walls may sound hollow when tapped, while wet plaster on masonry
walls makes for an all-round heavier, more solid structure.
D The weight is important to good sound insulation; sound waves are vibrations,
and it is hard to vibrate a heavy wall. Solidly built walls offer an obvious
advantage, while lightweight plasterboard-finished walls require more care.
Sound insulation can be improved by suspending only mineral fibre between the
stud partitions, which will absorb some of the sound (Domone, 2001: 6). Although
solid walls give good resilience against airborne sound, such as music and
voices, they offer little in resistance to impact sound, such as footsteps. Concrete
floors are particularly prone to impact sounds, but laying a resilient layer, such as
a carpet, onto the floor will guard against this.
D Isolating two structures is also important for good sound insulation, as it breaks
the sound path. Cavity walls in both house types perform this function. Floor
constructions can also be isolated with the use of a floating floor system. The two
parts are separated by mineral wool, which gives resistance to both impact and
airborne sound. A timber floor construction is lighter than a concrete floor;
therefore to achieve the same levels of sound insulation, additional layers of
board can be fitted to increase the total weight. An airtight structure is also
important for good sound insulation. It is pointless spending money on sound
insulation in either a timber-frame or brick and block house, if the sound can pass
around a partition through a poorly sealed window, door or service duct (Domone,
2001: 6).
D According to Lancashire (2008) both timber-frame and brick and block houses
have to comply with energy efficiency targets set out by the Building Regulations.
The minimum U-value (insulation level for each component of the building)
required for exposed walls is 0.45W/m2K. A standard brick and block house offers
a U-value of 0.43 W/m2K; whereas a standard timber-frame outperforms the
mandatory ratings, achieving a U-value of 0.41 W/m2K. The latter can be
improved to 0.29 W/m2K by increasing the frame size from 90mm (standard) to
140mm (enhanced), which increases the space for insulation. This gain is at
comparatively little extra cost.
32
D For conventional houses, plans are computerised. Builders can hand out
quotations on a large number of different house plans within minutes. For timber-
framed houses no such facilities exist. House builders work from quotations for
brick houses as a basis, and add onto those prices for timber-frame houses
(Scot, 2007: 22).
D From a builder's point of view, whether it is a future house owner or a speculation
house building company, the time it takes to complete a house is quite important.
A private house owner can save on alternative dwelling costs, and interim
interest, whilst a civil servant can do so on his/her subsidy. Similarly, building
companies can save the interest and possess a more favourable cash flow if time
can be saved on the building of a house (Lubber, 1986: 25). Builders indicate that
it takes about sixteen weeks to complete a conventional house. A timber-frame
house can be completed in seven days. For a building company, it was calculated
that after nine weeks, provided that the first houses are sold, no further loans are
needed to finance a building project of twenty timber-framed houses, which can
be completed in ten weeks. For the same company, a building project of twenty
conventional houses will take twenty weeks to complete. Provided all the houses
are sold when completed, the cash flow situation will be positive for the company
after twenty weeks (Lubber, 1986: 25).
.. A timber-frame house is usually wind and watertight by week five of the build;
thus, while the bricklayers work on the outside, work can begin on the internals.
By contrast, a brick and block house is not normally wind and watertight until
around week nine or ten, so work on the inside starts later in the building process
(Time Frame Builders Association, 2011).
a A timber-frame house gladded with bricks on the outside, will be as fire resistant
as any other conventional house. The literature on tests done in the United States
of America and Great Britain show that once a fire is out of control in one room of
the house, the fire will spread from there after about half an hour. This time lapse
is about the same for a brick house. All materials used for the construction of a
timber-frame house have to meet specific requirements and specifications. If
used correctly, all materials will last a lifetime (Lubber, 1986: 25).
a Because of the light-weight construction of a timber-frame house, especially when
no bricks are used, this building method is quite attractive for areas in which the
33
"""
soil is unstable. Internal walls rest on the floor and not on a foundation as in a
conventional brick house, and walls can be moved or taken out with much less
effort than those for a conventional house. An additional door can be fitted in an
internal wall by sawing the opening with any handy man's saw (Lubber, 1986:
26).
" Owing to the inherent unit strength, timber-frame houses are not affected by
shifting ground, which causes cracks in masonry walls. Shrinkage cracks caused
by drying out of conventionally constructed walls are also avoided. Face brick
finish and plastic rainwater drainage systems further reduce maintenance. Timber
has a better strength-ta-weight ratio to most building materials and this includes
concrete and steel. Timber-framed homes can therefore be built in areas where
soil movement occurs because of the varying water content. The light-weight
nature of a timber-frame structure, in relation to its strength, and combined with
its resilience, makes it able to withstand shock and stress, which would severely
damage a conventional structure (McRae, 2010).
" With a growing concern for the environment and global warming, it is in every
one's interests to keep energy demands as low as possible. Building energy
efficient, well-insulated homes to reduce fuel consumption and running costs is
essential. However, what many home builders do not realise is that even before a
house is built, the materials used in its construction have a Product Energy
Requirement (or PER), which refers to all the energy (expressed in kilowatt-
hours) that goes into producing and transporting a product (United States of
America. Department of Energy, 2000). Timber has the advantage of being
produced by natura) means, such as sun, water and air; thus its energy
requirements are all in the extraction and transportation of the logs from the
forest. A timber-frame wall in a typical three-bedroom detached family house has
a PER of around 7,450kWh, while a concrete block wall in the same property
requires 1.7 times more energy, with a PER of around 12,816 kWh (Scat, 2007:
22). Timber is also the only renewable structural building material available, and
the majority of timber-frame package companies invest heavily in well-managed
replanting programmes.
" All major insurance companies in South Africa are insuring timber homes. More
importantly, there is no additional premium for insuring a timber home as opposed
to insuring a similar brick and mortar home. Country Timber Homes is a certified
34
member of the Time Frame Builders Association (TFBA), which also extends
insurance to timber frame home owners (TFBA, 2011).
3.3 Conclusion
From the above-mentioned discussion, there are many differences between timber-frame
and brickwork buildings. Timber-frame buildings are as good as conventional buildings, if
not more so. The world of today is taking stringent measures to keep the cost of living
down and there is worldwide interest in maintaining energy demands as low as possible.
Therefore, building energy efficient, well insulated homes to reduce fuel consumption and
running costs would be of great benefit. A timber-frame home uses less energy as it is
usually warm in winter and cool in summer. Timber-frame construction honours the
environment; being made from a natural plan, it is a green building method. During its
production it does not cause hazards to the environment like its counterparts.
Timber-frame houses are functional like conventional houses. They perform the same
mandatory functions. The main difference is that a timber-frame house uses timber on its
walls while a conventional house uses stone or brick on its superstructure. They can both
use the same foundations and the same type of roofing. Timber-frame walls perform well
where the soil is unstable and cannot easily be affected by the shifting ground like a
masonry brick wall which usually forms cracks.
Timber-frame does not rely on the weather as much as more traditional techniques; that
said, in fair weather, a framed house can be completed anywhere between 5-10 days.
35
CHAPTER 4
4 THE ADVANTAGES OF WOOD-FRAME CONSTRUCTION
4.1 Introduction
Today, buildings are not constructed to protect men from natural elements and wild
animals only, but in such way that they are intended to create a healthy living
environment and a degree of comfort for all occupants. In addition, there are many
factors that can influence a homeowner's decision on the kind of end product he/she
needs. These factors include price, quality, durability and image.
It is perhaps not surprising that certain materials such as bricks and concrete blocks are
favoured when choosing a suitable building material for a house. This is because the
properties and characteristics of these materials are known. It is therefore necessary to
elaborate on the advantages and benefits of using timber-frame for houses. The
disadvantages of using timber will not be discussed in this chapter. Building materials are
preferred in terms of the sustainability of a building material. This needs to be considered
in terms of its energy use, its impact on the carbon cycle and its environmental impact.
Timber building is part of future energy-efficient building. Wood is sustainable, carbon
dioxide (C02) neutral and is a highly effective insulator, creating excellent living
conditions. One specific advantage of wood is its ability to reduce energy use. Timber
construction has a higher heat insulation value than conventional construction methods,
even with lower wall thickness. An external wall constructed using timber may have only
half the thickness of a brick or concrete wall and yet provide double the thermal
insulation (Anderson & Oberschulte, 1992: 4).
The key aim of this chapter is to discuss timber-frame properties and their advantages.
This assists not only homeowners but policy makers, developers and contractors to
choose the most suitable wall material for low income housing projects.
4.2 Wood is good for the environment
As a construction material, wood causes the least impact on the environment compared
with concrete or steel. It makes sense that building with wood, a renewable and natural
resource would have environmental benefits. This common sense judgement is now
being substantiated with scientific data. Life Cycle Assessment (LCA) is a 'performance
36
based' approach used to assess environmental impact. LCA quantifies the overall effects
of a product, process, or activity on the environment over its life time. (Central Mortgage
& Housing Corporation, 2009). This includes material extraction, manufacturing,
transportation, installation, use, maintenance, and disposal or reuse. Life Cycle
Assessment has shown that wood products offer clear environmental advantages over
other materials. When considering the environmental impact using Life Cycle
Assessment, wood outperforms steel and concrete in the following ways:
Embodied energy in production;
Emission of greenhouse gases;
Release of pollutants into the air;
Generation of water pollutants; and
Production of solid wastes (Central Mortgage & Housing Corporation, 2009).
4.3 Energy efficiency
If wood is burned as an energy source, the carbon stored in the wood combines with
oxygen and escapes into the atmosphere as carbon dioxide. With sustainable forest
utilisation, the carbon dioxide released is re-sequestered by the re-growing trees and the
cycle is closed. Thus, the concentration of carbon dioxide in the atmosphere does not
increase (Swiss Federal Office of the Environment, 2009).
Wood is 400-times less heat conductive than steel and 8.5 times less conductive than
concrete; therefore homes built with wood framing take less energy to heat and cool.
Wood construction can meet the energy codes of all climates. In extreme climates, such
as Alaska and the Canadian Arctic, the adoption of double wood-frame wall systems
keeps homeowners warm when temperatures drop in winter to -40°F. New energy code
requirements in several European countries have prompted a switch from traditional
masonry construction to wood (Western Red Cedar, 2012).
4.4 Timber-frame is a renewable material
As the world's only renewable building material, wood cannot only be recycled, but
regenerated as well. What is more, trees provide benefits to the environment while they
grow, taking in carbon dioxide and releasing oxygen (Central Mortgage & Housing
Corporation, 2009).
37
Wood siding substitutes, such as concrete, vinyl and aluminium are manufactured from
materials extracted from the earth and once removed, they can never be replaced. When
substitute sidings age beyond their useful life, they become part of landfills (Central
Mortgage & Housing Corporation, 2009).
4.5 Seismic quality
Light-frame construction can resist some shear or dynamic loads and, loading under its
limitations in an assembly plant, it would crumble. The seismic resistance of timber-frame
structures is relatively high, provided the quality of materials and construction are
satisfactory. Generally, the building tends to be lightweight, especially when compared to
brick or stone, which helps reduce earthquake forces on the structures. In addition,
because of the relatively large number of walls and the use of numerous nailed
connections, wood frame houses have traditionally performed well in earthquakes so that
deaths and serious injuries are rare (Arnold, 1995: 4).
Timber-frame is a more precise building method resulting in less wastefulness; the
nature of construction is such that it allows building right up to trees and shrubbery
whereas with brick construction, this is not the case. The seismic performance of wood-
frame construction is greatly enhanced by its non-structural components (Central
Mortgage & Housing Corporation, 2009). The architectural finishes and numerous non-
load-bearing walls increase the amount of energy the building can dissipate during an
earthquake because these additional systems absorb energy as they are damaged.
4.6 Flexibility
The flexibility of timber construction methods makes it easier to vary a buildinq's
orientation on site, its floor plan, the number of rooms, the interior design and the overall
appearance, while timber's thermal efficiency means walls can be slimmer, releasing up
to 10% more space than other building methods. External finishes depend on personal
preference; walls can be clad in wood, tiles, brick, or plastered; roofs can be clad in tiles,
slates, concrete or metal (Rackard, 2013).
Wood's immense flexibility as shown in Figure 12 where it forms a circular structure may
make it the best choice for specific and the easiest construction material for renovations.
Wood buildings can be redesigned to suit changing needs, whether this involves adding
a new room or moving a window or door. Making changes is virtually impossible when
38
walls are poured in concrete or when expensive and time-consuming reworking of the
construction material is needed off site (Grand Solution Manual, 2013).
Figure 12: Timber Structure to show that not only wood will produce straight panels but
also circular panels (Smit, 2003).
Wood is lighter than other construction materials such as masonry, concrete or steel;
thus it is easier to transport. It can be sized and cut on site, reducing the number of
workers and the amount of heavy lifting equipment needed on a construction site (British
Colombia Wood, 2009).
4.7 Durability and Adaptability
Light-frame construction can be very durable. However, the life span of a structure
constructed of wood, is relatively minuscule to that of one constructed of concrete or
masonry.
Homes that are tough and durable, beautiful and practical, timber-frame houses have
walls made of specially treated timber frames, lined with either reflective or blanket
insulation material, encased in a weatherproof cladding on the outside and a fire-rated
lining material on the inside. The outer 'skin' on a timber-frame home is not only
beautiful, but it is also very tough, weather resistant, impact resistant, corrosion resistant
39
and ultra violet (UV) light stable. It takes paint or varnish beautifully, providing a structure
that needs very little maintenance over the years (Smith, 2008).
As proof, the world is full of examples of ancient, wood frame buildings that remain
structurally sound such as Norway's beautiful Stave Churches, which were built
hundreds of years ago and are still in use today. In fact, extended service life is one of
the key advantages wood offers as a building material (British Colombia Wood, 2009).
4.8 Strength
Timber is strong in both tension and compression and has a high strength to weight ratio.
As with both steel and concrete, timber has physical limitations, but once these are
accommodated, it is possible to design structures of almost any size with it. Australia's
largest timber spans 100m, while buildings and bridges in other countries, such as
Europe and the USA span much further (SALMA, 1989: 46).
4.9 Aesthetic quality
As a building material, wood is incomparable in regard to its prettiness. What appeals the
most about wood is an aesthetic beauty as shown in Figure 13, which gives off a
timeless elegance and, durability as well as the way timber lends itself to craftsmanship
(Spencer, 1993: 71).
40
Figure 13: Timber-frame house in Bethlehem displays a timber-frame beauty (own
information)
4.10 Acoustic Performance
A timber-frame house is a warm, comfortable and safe place in which to live. Wood is a
natural, renewable resource that combines strength with versatility, and is an excellent
insulator. Timber-frame buildings can offer a better level of acoustic and thermal
insulation making them quieter and more comfortable to live or work in than other forms
of construction, if insulated well (Smith, 2008).
4.11 Insulation
Timber-frame, as a highly insulated lightweight structure, follows the principle of
conserving, within the external shell, the heat generated therein and in also preventing
the external cold and heat elements from penetrating and influencing temperatures
internally; that is to say, it keeps heat in, and keeps heat and cold out. With an insulated,
solid masonry construction, before heat generated internally can be enjoyed, it has to
41
warm up the structure. Once warmed, it will assist in keeping the internal area warm.
This however, takes a considerable time to achieve. An easy experiment to prove this
can be undertaken by merely putting a hand on an external wall inside a masonry built
house on a cold day when the inside temperature is acceptable. The wall will feel colder
than the room (Burchell, 1984: 83).
4.12 Less wastage of materials in timber-frame construction
According to Burchell (1984: 85), with a high element of prefabrication, fully engineered
and designed on a module to suit finishing materials, cutting and wastage of materials on
site are kept to a minimum. The savings on waste materials is clearly evident to the
experienced eye when seeing a well-run timber-frame housing site.
4.13 Dry Construction
Timber-frame is a form of dry construction where there is no drying out period and where
less water is required. Wet cracks do not occur in this type of construction, whereas they
are fairly common in wet construction. Dry construction can continue even in inclement
weather, such as in rain or snow (Kothmann, 2009).
4.14 Renovations and Alterations
According to Rudd (2006: 55), because timber frame is a light-weight structure, old
structures are easily able to accommodate the weight of the new section. A structural
engineer would need to be involved in the planning stage, but once he/she has approved
the existing building as being able to cope with the additional load, it is an easy, quick
and sensible way of extending a home. More often than not, occupants not have to move
out of the house during the construction phase. Houses need to be able to adapt to
changes in the life stages of their occupants, as well as to wider changes in the way
people live.
A loft conversion is possible only with timber, where the low net weight and exceptional
strength of wood elements ensure adequate load-bearing, even over considerable spans.
Timber construction reduces the building time for extensions, and the light weight of the
components means they can be delivered to sites even with severely restricted access.
With proper planning, not only windows and doors, but also many domestic installations
can be integrated at the prefabrication stage (Rudd, 2006: 56).
42
4.15 Life expectancy of timber-frame houses
Today the average service life of a wooden house is between 80 and 100 years, with
some builders guaranteeing a lifetime of 125 years. In fact, timber houses can last many
hundreds of years, as can be witnessed from the many surviving examples from the
middle ages.
In the Western States of America, over 90% of all one family dwellings are constructed of
timber-frame. In Scandinavia, the figure is 80%. How long will timber-frame last? This is
a fairly common question asked when discussing timber-frame houses. The answer is
that a timber-framed house, properly designed and constructed, can last for many years
if treated well from fungus and termites. It will last as long as the same house properly
designed and constructed in traditional masonry (Burchell, 1984: 14).
43
Table 4: Summary of some of advantages and potential problems of timber construction
ADVANTAGES OF TIMBER POTENTIALPROBLEMSOF TIMBER-
CONSTRUCTION CONSTRUCTION
1. QUiCKerection time . Traditional procurement process
2. Reduced site labour T2. Additional design and engineering time
3. Reduced time to weather the structure 3. Modification of general arrangement
drawings if based on masonry construction
4. Low embodied energy if constructed in l4. Lack of experience of following trades.
local timber
5. Recyclable 5. Lack of experienced builders and trades
6. Low volume of waste on site requiring 16. Susceptibility to decay of timber when
removal Iexposed to excessive moisture.
7. Can be built to exceed 60 year design 7. Deficiency of site quality control
life
8. Energy efficient when constructed to 8. Combustibility of timber requires vigilant
current standards quality control to achieve required fire
Irating of separation and compartment
walls.
9. Fast heating due to low thermal mass
10. Reduce construction waste through
efficient control manufacturing
11. Reduced time on site reduces
environmental nuisance and disruption to
local residents.
12. Reduced construction time translates
reduced risk exposure
(TFBA, 2011).
4.16 Conclusion
It is perhaps not surprising that building with wood has many advantages. In this chapter
the effectiveness of building with timber has been proved. Wood is lighter than
conventional construction materials such as concrete, masonry and steel. Its light-weight
properties mean that it can be delivered to sites with restricted access, thereby reducing
the number of workers and the amount of heavy lifting equipment needed on a
construction site. The light-weight and modular structure of timber houses, make it easier
44
to add an extra floor or an extension. This is a simple practice and the dry lining used in
timber construction means less waste and moisture.
Unstable soil conditions such as clay and dune sand that require additional re-
enforcement when building with bricks and mortar are suited to timber construction.
Timber buildings are warm in winter and cool in summer. Their thermal efficiency is as
much as 6 to 8 times greater than that of masonry construction. Timber buildings are
environmentally friendly and therefore ideally suited to mountain-side plots, and eco-
sensitive areas resulting in very little disturbance to the existing vegetation. Furthermore,
timber buildings minimise site excavation and costly access with heavier materials.
The use of timber-frames in RDP houses is possible because of the many advantages
that timber displays. Timber has many qualities which are advantageous.
45
CHAPTER 5
5 LOW INCOME HOUSING IN SOUTH AFRICA
5.1 Introduction
According to the United Nations more than one billion people do not have access to
adequate housing, and yet housing is recognised as a basic human need (UNHABITAT,
2001: 6). In an effort to realise this right, the South African government has embarked on
a housing program to replace shacks with low cost housing for families whose sole
provider is unemployed or whose combined monthly household income is below R3 500
per month. These houses are called Reconstruction and Development Programme
(RDP) houses. They are usually built on the outskirts of cities where large pieces of land
are available. They consist of simple single storey structures, constructed with bricks and
mortar. Each is big enough to house a single family.
The South African government, through the RDP system has provided around three
million homes to South Africans since the end of apartheid (1994). Those living in shacks
on less than an inflation-adjusted amount per month are entitled to apply for RDP
housing. The waiting period can be as much as 10 years (Ali, 2013). Only South Africans
are eligible to apply and there are certain requirements that one needs to comply with
before receiving a RDP house.
The government is however, faced with difficulties of delivering quality low income
houses in the specified time and budget, due to the rapid rate of urbanisation. This again
is the consequence of large numbers of poor and unemployed people migrating from
rural areas to the major cities, seeking employment. On realising that they cannot afford
to buy or rent houses, they opt to move into shacks or tents in informal settlements.
Occasionally people who have benefited from RDP houses will sublet their properties
and move back into their shacks. Their spouses might reapply for an RDP house and in
some instances they will get another house in this way. In some cases the houses are of
poor quality and need urgent repairs. These cases cause delays for people to obtain
houses on time, making the backlog even more difficult to eradicate.
This chapter examines housing in line with international bodies such as the United
Nations and the South African government's approach to low cost housing. It further
investigates some of the problems that lead to the slow delivery of Reconstruction and
46
Development Programme houses. Also under investigation are alternative building
materials or technologies, which should all meet the required acceptable levels of quality,
norms and standards, while still facilitating rapid housing delivery.
5.2 Housing as a human right and the South African Constitution
A lack of adequate housing in the cities of developing countries is one of the most
pressing problems of the 21 st century. According to the United Nations Habitat (2001),
over one billion people are estimated to live in "inadequate housing conditions in informal
settlements without security of tenure and in conditions that can be described as life and
health threatening". Between 40% and 70% of the population in most African cities live in
informal settlements (Roseland, 2000).
Section 26 of the Constitution of the Republic of South Africa, 1996, states that everyone
has the right to "access to adequate housing". It is the government's duty to take
reasonable legislative and other measures, within its available resources, to achieve the
progressive realisation of this right. Provincial legislatures and local government share
the responsibility with the national government for the delivery of adequate housing. The
Constitution also states that "No one may be evicted from their home, or have their home
demolished, without an order of court made after considering all the relevant
circumstances. No legislation may permit arbitrary evictions" (South Africa. Department
of Local Government & Housing, 1994).
Section 27 (c) Chapter two of the Constitution of the Republic of South Africa of 1996,
states that everyone has the right to social security, and if they are unable to support
themselves and their dependants, appropriate social assistance will be provided (South
Africa. Department of Local Government & Housing, 1994).
5.3 Reconstruction and Development Programme (ROP)
The Reconstruction and Development Programme is a South African socio-economic
policy framework implemented by the African National Congress (ANC) government of
Nelson Madela in 1994 after months of discussions, consultations and negotiations
between the ANC, its alliance partners the Congress of South African Trade Unions and
the South African Communist Party, and mass organisations in the wider civil society
(Pillay & Naude, 2004).
47
The Reconstruction and Development Programme (ROP) is an integrated, coherent
socio-economic policy framework. It seeks to mobilise all the country's resources towards
the final eradication of the results of apartheid and the building of a democratic, non-
racial and non-sexist future. It alleviates poverty and provides better social services to
previously disadvantaged South Africans (White Paper, 1994). The ROP sought to:
1. Meet the basic needs of the population (including shelter);
2. Develop human resources;
3. Build the economy;
4..Democratise the state and society (Rabbani, 1994).
The ROP endorses the principle that all South Africans have a right to a secure place in
which to live in peace and dignity. Housing is a human right, as stated in Section 26 of
the Constitution of the Republic of South Africa of 1996. One of the RDP's first priorities
is to provide for the homeless. At this time, the government has managed to provide
around three million homes to South Africans since the end of apartheid (Ali, 2013).
5.4 ROP housing allocation
Every South African citizen is entitled to a roof over his or her head. This is the
government's mission through ROP housing which provides adequate housing for all
South African citizens as a priority to ensure that the basic human rights to shelter, water,
electricity, health care, sanitation and access to education are met. This mission is
implemented through the building of cement brick houses to replace the shack dwellings
that are seen all over South Africa's townships.
A person is eligible for a housing subsidy subject to the following criteria;
o Household income not exceeding R3 500 per month;
o South African citizen or permanent resident;
o Legally competent to contract (over the age of 21 and of sound mind);
o Married or cohabiting;
o Single with dependants;
o Acquiring a home for the first time and
o Has not previously received a housing subsidy (Pillay & Naude, 2004).
The following are requirements for application for an ROP house at the municipal office:
o Certified copy of applicant's Identity Document.
48
• Certified copy of the spouse or partner's ID (Identity Document) when the
applicant is married or cohabiting.
IJ A copy of the death certificate in the case of a widow or widower.
• The applicant and spouse or partner must provide proof of income (payslip) if
employed.
o The applicant and spouse or partner must be South African citizens with legal ID
documents.
o Certified copies of dependant's birth certificates or ID documents.
o Applicant must sign an affidavit.
o Affidavit must be signed by spouse or partner (Greyling, 2009: 8).
When the housing subsidy policy was launched in 1994, government promises of
delivering "one million houses in five years" were heard by many as political posturing
and post-democratic bravado. And yet, the sceptics were proven wrong as one million
houses were indeed delivered, albeit within seven years. By 2010, the Department of
Human Settlements estimates that it has delivered somewhere in the region of 2.8 million
houses to qualifying beneficiaries throughout South Africa (Tomlinson, 2007).
Nonetheless the country's housing deficit has grown to 2.1 million households, the
number of informal settlements has skyrocket to more than 2, 600 sites, and there are 1
million urban poor families living in simple shacks in informal settlements (Tomlinson,
2007). This leaves the Department of Human Settlement faced with a housing backlog
that needs to be eliminated.
5.5 Housing backlog
In 1994, South Africa first democratically elected government inherited the housing
backlog of 1.2 to 2.5 million units as well as the rapid expansion of informal squatter
settlement (Karseens, 1999). Current estimates of the backlog stand at about 2.1 to 2.5
million units. As at September 2011, it was estimated that approximately 12 million
people were still without adequate housing. Though consistent and reliable statistics on
housing are somewhat irregular, 12.8% of South African households lived in a ROP or
state-subsidised dwelling, while 13.5% of households have at least one member of the
household on a demand database or waiting list for state-subsidised housing according
to the 2009 General Household Survey (Masilela, 2012). Some of the reasons for this
housing backlog are natural population growth, a trend towards urbanisation, high
employment, and inadequate delivery to address historical backlogs. According to the
49
Department of Local Government and Housing (2005:8) low levels of delivery are caused
mainly by insufficient resource allocation and under-spending due to capacity restraints.
As a result the backlog remains difficult to remove.
Nonetheless, the Department of Human Settlements has recognised that the backlog in
South Africa is not being reduced fast enough and has committed to increase the rate of
delivery with a view to wiping out the backlog by 2030. The fastest rate of delivery can
also be acquired by using alternative building materials rather than traditional masonry
bricks and mortar. Timber-frame as wall system might give a practical solution to slow
delivery and poor quality. This is due to the fact that wood is an economical alternative to
higher priced structural components, such as steel or concrete while it can also be
constructed faster.
5.6 Building material for ROP houses
Building components and building materials have different service lifetimes regarding
aesthetic, economic, functional, physical and technical performance over time (Civil
Engineering Portal, 2012). It is therefore important to choose the appropriate materials
for a house so that durability, stability and aesthetic properties can be achieved.
All RDP houses are 36m2 (square meter) and consist of strip foundations. Walls are built
of bricks or concrete blocks, depending on the local availability of building material. Floor
construction is the ordinary concrete surface bed with laminated vinyl tiles as floor
finishes. The roof is corrugated iron roof sheeting. Walls and foundations play an
important role in the stability of the structure as well as in the percentage of the total cost
and construction time (Civil Engineering Portal, 2012).
Since walls are vital in the construction of a house, alternative wall techniques such as
timber-frame walls may be considered on RDP houses. The hypothesis is that timber-
frame walls are very cost effective, economic and quick to construct. This may therefore
help to eradicate the slow delivery of houses as cost reduction is achieved by the
selection of more efficient materials or by an improved design.
5.4 Conclusion
Shelter is considered as one of the basic human needs, yet even today most people still
live in inadequate housing such as informal settlements and shacks. The South African
50
government has sought to address the housing crisis directly through the delivery of
subsidised housing for low income households, which is fulfilled through the
Reconstruction and Development Programme (ROP). The South African government
provides a subsidised housing unit to eligible households. Eligibility hinges on people
with dependents, resident in South Africa, earning less than R3 500 per month, and who
had never owned a home before. These units are usually erected with bricks and mortar.
Although the goal of delivering one million units in five years was realised, the SA
government is still faced with housing problems. A large and ever-increasing housing
backlog is evident. The causes of this include urbanisation, high unemployment and
inadequate delivery to address historical backlogs. As a result housing authorities
struggle to cope with severe housing shortages. There is clearly a need to use a building
material that is fast to erect, durable and cost effective and the idea of using timber-frame
walls as alternative to traditional masonry bricks and mortar walls on ROP houses was
prompted.
UV·UFS
51
BLOEMFONTEIN
BIBLIOTEEK • U8RARY
CHAPTER 6
6 COMPARATIVE COST ANALYSIS OF TIMBER-FRAME AND BRICK WALL
CONSTRUCTION
6.1 Introduction
The slow delivery of houses (ROP) and the growth of slums in South Africa need to be
dealt with. The Department of Human Settlements (RSA) has undertaken investigations
in respect of alternative building technologies which will have all the requisites for quality,
norms and standards and still facilitate rapid housing delivery. Building cost-effective
houses may help to improve housing delivery. As a result timber-frame walls could come
to the rescue, if investigated more thoroughly and given a chance.
Wood light-frame construction is known for its great economic value. Its materials are
abundant, easily obtained, and there is a minimum amount of labour needed for
construction (Pringle & Bruce, 2011).Timber-frame houses have low running and
maintenance costs, even over a long period of time. Not only will timber-frame
construction make good economic sense, it can also make social sense as well, as there
will be a reduction in defects and accidents. This is mainly because a timber-frame house
can be pre manufactured in the factory (Pringle & Bruce, 2011). In this regard, timber-
frame should be the preferred building techniques for low income housing.
'Timber cost, like any commodity varies hugely. Factors, such as the size of the building,
how complicated the structure is going to be and the specification will play an important
role in how expensive the wood will be. Additionally, the building materials that make up
the timber-frame structure such as gypsum board, insulation and cladding materials will
play a vital role in the cost of the timber-frame wall (Holz, 2010: 19). Other aspects that
affect the cost of the wall will be labour, overheads and management costs. There will be
fewer labourers needed to erect a timber-frame wall than for that built of brick and
mortar.
In this chapter, the cost of constructing a masonry brick wall and a timber-frame wall is
compared. The two walls were of the same floor area 50m2 (see Appendix C). For the
purpose of the research, a wall of 6.250 m (metre) in length and 2.550m in height (a wall
of 15.94 m2 in total) is used as an example to discuss and explain the different costs and
cost implications. The method of price per square metre is used. It consists of multiplying
52
the wall area (gross area less area of openings) by known quantities of material required
per square metre. The different rates were evaluated to determine which method of
construction is cheaper. No waste factor was taken into consideration. The purpose of
this cost analysis is to prove that using timber-frame as alternative to a masonry brick
and mortar wall in RDP houses can be cost effective, as well as an economic solution to
the slow housing delivery. In addition to the above hypothesis, these houses will be of
good quality and can be delivered on time.
The case study (timber structure is cheaper than steel structure) by Keith Kothmann
(2009) will be analysed to prove that not only is timber-frame structure cheaper than
masonry brick and blocks but it is also less expensive than a steel structure. Kothmann's
study shows clearly that wood frames are a better solution to the expensive conventional
materials, which are also non-renewable.
6.2 The comparison of a masonry brick wall and a timber-frame wall
The comparison of the cost of masonry brick and timber-frame wall was analysed in
order to find which method is the cheapest. The cost implication of the project was noted.
The most economical solution would be the one preferred to build RDP houses.
6 .2 .1 The cost of a wall constructed with the masonry brick and mortar method
The wall area method of estimating will be used because of its simplicity and accuracy. It
consists of multiplying the net area of 110.69 m2 - 17.63 m2 = 93.06 m2 (gross area less
the opening) by known quantities of material required per square metre. In this exercise,
the wall was without windows and doors. The prices that were used for this exercise
were obtained from Cashbuild in Bethlehem Free State on 17 November 2012.
53
A Sample of brick wall of 220mm Appendix C (6.25mx2.55m) = 15. 94 m2 will be
used.
Factor calculations - see Appendix C (Afrisam, mixes of all concrete)
Mortar in a brick
0.220mm + (0.085mm x 2 faces) = 0.39 mm x 0.11Omm= 0.0429/ Brick wall
Material (mortar)
Sand 1 .22 x 0.043 (factor per m3) @ R 236.75 = R12.42
Cement 8.33 x 0.043 (factor per m3)@R 71.05 = R 25.45
Labour mixing 9 x 0.043@ R19.00 = R 7.35
R 45.22
Material bricks
Brick force (2mm/15mm) @ R14.87 per m2 = R14.87
Brick Cement Stocks 105 @ R980/1000 = R102.90
R104.64
Labour Building
Bricklayer 1.41 x1.20 @R30.00 = R50.76
Labourer 1 .41x1.20 @ R18.00 = R30.46
R81.22
Total R231.08
Plant (1%) = R2.31
R233.39
Overheads (4 .5%) = R10.50
TOTAL COST OF THE BRICK WALL = R243.89 per m2
54
6.2.2 The cost of wall constructed with timber-frame wall system
The prices that are used for this calculation were obtained from Timber Home Kits in
Johannesburg on 03 November 2012.
• Frame:
Galvanized drywall channel@ R201.65 per no 1- per Im: R201.65 x 6.00m = R1209.9
(76mm x3.6mm)
Galvanised head channel@ R233.70 per No 1-per Im: R233.70 x 2 = R467.40
(76mmx3.6mmx3m long) R1677.30
Drywall Stud
(51mmx2.7mm) @ R39.52 per No 1- no 1 per Im: R39.52x6.00 = R237.12
Drywall track @ R42.20 per N01- per Im: R42.20x2= R84.4
(51mmx 2.7mmx 3m long) R321.52
• Internal Cladding:
12mm BPB Gypsum board used @ R170.32 x 6No = R1021.92
Internal walls (2.4m x 1.2mWide)
• Insulation:
50mm Aerolite insulation in @ R17.71per m2 x 165.94 m2 = R2938.79
between panels
• External cladding:
OSB Board Chipboard@ R282.41x6No = R1694.46
= R7653.99/15.94
Total cost per m2 = R480.17 per m2
Add:
Labour Building
Carpenter 1.41x1.20@R30.00 = R50.76
Labourer 1.41 x1. 20 @ R18.00 = R34.46
R565.39
55
Plant (1%) = R5.65
R571.04
Overheads (4 .5%) = R25.70
Total cost m2: = R 596.74 per m2
6.3 Cost comparison of construction of ROP house walls
The cost of the wall of a ROP house will add up to R 22 696.40 (R243.89 per m2x 93.06
m2) if the ROP house is constructed with bricks, while a timber-frame will be R 55 532.62
(R596.74 per m2 x 93.06 m2). The cost includes material and labour. It is based on
external and internal walls and not the other building elements, such as roofs, doors,
windows and foundations. Other factors that contribute to the price of a house, such as
electricity and water were not considered.
6.4 Kothmann Case Study
As the South African government cannot deliver ROP houses on time for the low income
groups in South Africa, other options should be investigated. Preference should be given
to a wall construction that is faster, affordable, safe and easy to maintain. Wood-frame
construction meets all of these requirements, and is proving to be a more cost-effective
option especially when compared with other wall systems. To emphasise further the cost
effectiveness of timber-frame, Keith Kothmann's 2009 study was analysed. The study
was chosen from other studies because the purpose of this research is to find alternative
construction that is easy, fast and can reduce the building costs. At the same time, the
quality and durability of the structures will not be compromised. Moreover Keith
Kothmann's case study is based on actual experience and not theory, which makes it
more reliable. This study shows that timber-frame is less expensive than steel-frames.
6.4.1 Case study (timber structure is cheaper than steel structure)
Keith Kothmann (2009) prepared a cost analysis for a one floor, 73,557 square metres
elementary school which had been built in 2002 in Flower Mound, Texas in the USA.
Kothmann is a Certified Professional Estimator, an engineer and former general
contractor from Fort Worth, Texas, with more than 25 years of construction experience.
To provide a fair comparison with no design or appearance changes except the gym
ceiling, Kothmann compared three wood-framing options to the as-built post and beam
56
steel structure. His results showed that the initial cost of construction could be
substantially reduced by changing the superstructure of the school from steel to wood.
Kothrnann's study also determined that the life cycle savings realised from the additional
thermal resistance provided by the wood roof system would save the district almost
$150, 000 (R1,407,OOO.00)equivalent or more per year in energy costs. This is in
addition to the reduced energy consumption from the wood framed walls (Kothmann,
2009).
57
KOTHMANN'S FINDINGS
Table 5: Kothmann's findings
Savings Total % Annual Completion
per Savings Savings Energy Time Savings
Square over Savings
metre Steel with
Wood
Walls
Option B: Wood roof framing
with wood studs
(Type VA) Saves
• Steel columns remain
• Change from steel to glulam $28.2 $2071600 6.6% $13000 5weeks
beams
• Change from steel bar joists
to wood I-joists
• Change from metal deck to
rated sheathing
system
$60.7 $4462840 $35.76%
58
The duration of construction is another key consideration in the planning of facilities. The
Kothmann study analysed the direct cost of reducing construction time by building a
wood-frame rather than a steel-frame or concrete facility (Kothmann, 2009). The study
found that the project duration of the wood-frame Option A is two weeks less than a
conventional steel structure. Wood frame Option B saved five weeks, and Option C
resulted in completion 12 weeks earlier than a steel frame building. While the study did
not calculate the benefits of earlier occupancy, there are obvious financial benefits
associated with a shorter construction schedule (Kothmann, 2009).
The study shows that speed is one of the key benefits of wood-frame construction. Wood
products are readily available and usually delivered more quickly than steel, which is
often shipped from overseas. Additionally, wood-frame assembly is fast; contractors can
often install wood members using boom trucks and other readily available construction
equipment instead of cranes, which speed up construction and further reduce costs (Roy,
2004).
6.5 Conclusion
According to the cost analysis between traditional brick and mortar and timber-frame
carried out in this chapter, the hypothesis that timber-frame walls are more cost effective
than brick and mortar walls is incorrect. Brick and mortar walls are cheaper than timber-
frame walls. A brick wall is made up of fewer items, while wood-frame has many items
that are costly. Timber-frame walls may become durable if treated well and taken care of,
while only paint is required to maintain masonry walls. Based on these results, masonry
walls would be the most economical solution and the best option for ROP houses.
The Kothmann study observed that timber-frame buildings are more cost effective than
other conventional buildings such as steel-frame houses. It emphasises that there are
other factors excluding price itself that contribute to the cost of the building. The speed of
construction is one factor that can save money. It makes timber very responsive to
market demands. Kothmann discovered than it was quicker to construct a timber-frame
structure than a steel-frame structure. This can save time for expensive labourers, skilled
workers and it can reduce rentals. Thermal resistance is almost as important in any
building as time because every household should save energy.
Timber-frame construction makes good social and economic sense because of the
reduction in defects and accidents that can be achieved through this form of site
59
construction. For builders, successful timber-frame construction involves a more efficient
building process with greater supply chain integration and less waste, thus saving many
thousands of rand on building costs.
60
CHAPTER 7
7 THE RESEARCH METHODOLOGY
7.1lntroduction
Timber-frame and masonry brick-wall construction were discussed in the previous
chapters. The different wall construction systems have different advantages that attract
the developers and homeowners. The cost comparison of timber-frame walls and
masonry brick and mortar walls were conducted in order to determine which wall system
is the more cost effective and economical. The most economical wall construction may
be used as an alternative to traditional brick walls on RDP houses.
Since timber-frame housing construction in South Africa is less prevalent than any other
form of construction a thorough investigation needs to be conducted to see if the general
public is familiar with, or will accept timber-frame construction. Building professionals
have a major influence on the type of materials to use. They usually select material
according to its structural strength, structural stability, special requirements, thermal
performance, acoustic performance and durability. To learn of these professionals'
perception and that of the general public towards timber-frame housing, a survey was
conducted.
The survey in the form of questionnaires will help to obtain information about people's
behaviour and thinking. It will help capture what people say about their opinions and
interpretations. This will be implemented by involving qualitative data that are obtained
through methods, such as interviews, on-site observations, and focus groups that are in
narrative rather than in numerical form. Such data are analysed by looking for themes
and patterns and involves reading, rereading, and exploring the data (Maxwell, 1996:6).
How the data are gathered will greatly affect the ease of analysis and the efficacy of the
findings.
Interviews with two contractors who have exposure and experience in building RDP
houses were conducted, primarily because their thoughts and willingness to change
. would help to promote a better understanding of timber-frame construction and its
growth.
61
7.2 Methodology
Maxwell (1996) argues that methodology is a tool or a way to solve problems and
thereby gain new knowledge. Everything that helps the researcher to reach his/her goal
is methodology.
The research is chiefly based on a literary study to establish whether timber-frame wall
construction is a better alternative to brick walls construction in South Africa. The aim is
to determine whether timber-frame walls would be appropriate for RDP houses, as well
as to analyse timber-frame as method of construction and building material. To discover
more about the problem and sub-problems, a literature study is supported by
questionnaires, interviews and field observations.
Three methods of investigation were used:
(i) The literature investigation regarding timber-frame construction was undertaken by
reading relevant books, timber manuals, magazines, journals, newspapers, the TFBA
and SALMA publications and electronic data. Engineering and building regulations'
(SANS 1200 and NBR- SANS 10400 - F: 2010) were consulted to ensure compliance
with standards.
ii) Questionnaires were distributed or ernailed to key persons including architects, the
general public, contractors and engineers.
(ii) Interviews were conducted with contractors, who have previously built RDP houses.
(iii) Field observations were done of housing projects that have been built with brick and
mortar.
Thus, the idea of combining these investigations with interviews makes the study more
reliable and realistic.
7.3 Qualitative research
The research attempts to gather an in depth understanding of people's behaviour and
perception towards timber-frame buildings and the reasons that govern such behaviour.
Thus, qualitative data were able to fuifiII such a mission. Shank (2002) defines qualitative
research as "a form of systematic empirical inquiry into meaning". By systematic he
means 'planned, ordered and public'.
Qualitative research methods were developed in the social sciences to enable
researchers to study social and cultural phenomena. Examples of qualitative methods
are action research, case study research and ethnography. Qualitative data sources
62
include observation and participant observation (fieldwork), interviews and
questionnaires, documents and texts, and the researcher's impressions and reactions
which are used in this research (Myers 2009).
Qualitative research has the following characteristics:
o Natural setting as source of data;
o Researcher as key instrument of data collection;
o Data collected as words or pictures;
o Analyses social settings and the individuals who inhabit them;
o Analysis of data inductively and, attention to particulars;
o Focus on participants' perspectives and how they make sense of the world;
o Contextualisation of findings, meaning is context-dependent;
o Use of expressive language;
o Persuasion by reason; and
o Need to view social phenomena through eyes of those studied; thus wary of
imposing frames of reference on participants a priori as this could be
inappropriate (RusselI, 2003).
7.4 Questionnaires
Questionnaires are the best known of the research instruments used for gathering
information from people and they can be used in conjunction with other techniques such
as interviews (Kotier, 1998).
In this study, the questionnaire was based on the literature review of chapter 2 up to
chapter 6. The survey questions were designed in a way that the respondents could
answer in an almost unlimited number of ways. This would assist the respondents to
express themselves without difficulty and increase the chances of obtaining information
that could be associated with the real situation. This type of survey is called open-ended
questions and was designed to gather information about timber-frame walls as an
alternative to brick-wall construction.
The questionnaires consisted of the following two sections:
Section A: - Background (biographical) information. This section of the questionnaire
referred to background or biographical information.
63
Section B: - This section of the questionnaire explored the participants' attitudes, habits
perceptions and preferences, if any, with regard to timber-frame construction in South
Africa.
Two groups of people were chosen for the study and these were the general public who
might not have any technical expertise about timber-frame and brick-wall construction.
The other group was building professionals with a high level of knowledge about these
two methods of construction.
7.4.1 Questionnaires to the building professionals
The structural questionnaire was distributed among a small, but carefully targeted
sample of professionals. These included a number of architects, engineers, contractors,
developers and quantity surveyors who have some level of understanding or interest in
timber-frame construction. A brief and clear explanation, together with a photo of timber-
frame house built by Timber Frame Builders was shown to those who were not familiar
with timber-frame houses, especially the members of the general public. Thirty-four
questionnaires were sent out to the building professionals through emaiIs and some were
personally delivered at the place of work. Table 6 and Figure 14 below show the number
of questionnaires sent out.
Table 6: Number of questionnaires sent to the professionals
Category INumber 1Via Email IDelivered by hand
Architects 6 4 2
Developers 13 3 I
Contractors 8 6 2
Structural Engineers 10 I9 f1
Quantity Surveyors 7 2 5
Total 134 124 ----- 110
64
Questionnaires issued to Professionals (Total=34)
• Architects
• Developers
Contractors
• Structural Engineers
• Quantity Surveyors
Figure 14: Questionnaires issued to professionals
65
Table 7: Categories of building professionals respondents
Professional Qualification Years of ]Number
Affiliations Obtained experience
Architects B ArchitectOre 15 1
rB Architecture 11 11
B Honours in Architecture 4 1
Developers BSc Property Development 8 1
1
BSc Quantity Surveying 13 1
Contractors iB Tech Civil Engineering 110 12
Diploma in Civil Engineering 13 1
IBSc Civil Engineering 6 ,2
Diploma in Civil Engineering 5 1
Structural BSc Civil Engineering 7 3
Engineers
BSc Civil Engineering 17 2
I BSc Civil Engineering 9 4
Quantity Sorveyors BSc Quantity Surveying 12 3
BSc Quantity Surveying 9 1
Total 24
66
IResponses from Professionals (Total=2411
"Architects
evelopers
Contractors
~tructural Engineers
uantlty Surveyors
Figure 15: Responses from professionals
I Professionals' Work Experience (Years) I
12 .-------------------------------------~~-----------------------
10 +------------------------------------
III
igii 8+------------------------::;------------
'iii
III
Jel! 6 +----------
.I.l...
o 4 +--------------------
o
Z
0-4 5-8 9-12 >12
Years of Work Experience
Figure 16: A bar chart showing years of experience of the building professionals
Table 7, Figure 15 and Figure 16 above demonstrate the participants who filled in the
questionnaires and are characterised according to their disciplines, qualifications and
years of experience. Only twenty-four people responded. The questionnaire under
discussion is attached and can be seen in Appendix A.
67
7.4.2 Questionnaires to the general public
The structural questionnaire attached in Appendix A, was circulated among the general
public, with a brief explanation of what a timber-frame wall is. A photo of a timber-frame
house built by Timber Frame Builders was shown to those who were not familiar with
timber-frame houses. Only those who understand English were selected. Some are
professionals outside the construction industry and others are not employed. A total of
twenty questionnaires were sent out to the general public at the place of work, shopping
malls and churches.
Table 8: Questionnaires handed out to the general public
Categories Via Email Delivered by hand
Accountants 1 2
Human Resource Officer 1
Secretaries 1 2
Police Officers 1 2
Not employed 10
Total 4 16
Questionnaires issued to General Public (Total=20)
• Accountants
• HR Officers
• Secretary
• Police officer
• Unemploved
Figure 17: Questionnaires issued to the general public
68
A total of seventeen questionnaires were received from the participants as shown in
Table 9 and Figure 18 below.
Table 9: Categories of general public responded
Categories Number
Accountants 3
Human Resource Officers 1
Secretaries 2
Police Officers 3
Not employed 8
Total 17
IResponses from General Public (Total=1711
• Accountants
• HR Officers
• Secretary
• Police officer
• Unemployed
Figure 18: Responses from general public
7.5 Interviews
Interviews are especially suitable when the problem is complex, since the interviewer can
rephrase the questions, as well as pose related questions to penetrate the problem
69
(Roos, Woxblom & McCluskey, 2010). With the possible difficulty involved of how to
express uncertainties in mind, personal in-depth interviews were conducted.
Messrs Thulane Baloyi and Peter Tshabalala, who work for small construction
companies, but with extensive experience of between four and eight years respectively,
were interviewed. They work at companies that have built most of the RDP houses in the
Qwa-Qwa and Bethlehem areas. Mr Baloyi's interview was on 06 September 2011 at
10hOO at his office in Bethlehem while Mr Tshabalala's interview took place at 11hOO, 10
September 2011 in Qwa-Qwa at his house. The interviews lasted about forty-five minutes
with each individual. The reason for choosing the two contractors was to establish
perceptions regarding this alternative method of construction. The aim was to discover
how much they knew about timber-frame construction; and the possibility of using timber-
frame for low income buildings. The question posed was: Would it be possible for them to
learn and adapt easily if the government proposed this alternative type of wall?
The interview questions were based on the literature studied about the timber-frame and
brick-wall method of construction. The questions were created with the intention of
keeping the interview process on track; part of what McCracken (1988) refers to as the
'grand tour' where 'prompts' are used to recover subject areas being missed. This
involved asking broad, non-directive questions which allowed the respondents to reply in
a manner which reflected his particular context, experience and understanding. This
method of questioning allowed the respondents to recall and explain in detail
experiences in the building industry.
7.6 Field Work
Observations on the current project took place at various times between 2009 and 2012
in Bethlehem and Lesotho. They were done in order to identify how long it takes to build
a timber-frame house and a masonry block or brick and mortar house. The approach
produced gratifying results as the two methods were witnessed both during construction
and as final products. In addition, the television programme 'Extreme MakeOver' (Dstv,
channel 174) was very helpful demonstrating how a wood-frame house is constructed in
a short amount of time.
70
7.7 Conclusion
This chapter discussed the research methodology employed in this study, as well as the
benefits of using the instruments of data collection, such as questionnaires, interviews
and a field study. Given the context in which this study is founded, the researcher is
confident that the data gathered throughout the course of this research, are reliable and
valid. Chapter eight will discuss the findings of the data.
71
CHAPTER8
8 FINDINGS
8.1 Introduction
This chapter focuses on the data collection and analysis. An analysis is done on the
basis of the data which have been collected through questionnaires and interviews in this
study and a discussion will ensue with the help of tables, charts and graphs. This is
mainly to make the results easy to understand. Details are given in the paragraphs that
follow.
8.2 Data collection procedure
Data have been collected through questionnaires (see Appendix A) and interview (see
Appendix B). The questionnaires were emailed, hand-delivered and then collected by the
researcher from 34 building professionals and 20 members of the general public. Only 24
questionnaires were completed and returned by the professionals, with the other 17 filled
in by the general public. The aforementioned data have been analysed through a
statistical analysis system (SAS) .The programme is very advanced and accurate. The
results of the analysis are given in the bar chart (Figure 19) and in Table 10 below.
8.3 Questionnaires to the building professionals
In the questionnaires completed by the building professionals, 100% of the participants
had seen timber-frame houses previously. Only 50% of these professionals, as illustrated
in Figure 19, were educated about timber-frame structural design and on the behaviour
of timber in adverse weather conditions. Furthermore, structural engineers agreed that
because of its light weight, it can resist some shear or dynamic loads. This helps reduce
earthquake forces on the structure. All the respondents agreed that its light weight could
be an advantage over steel and concrete and for its great economic value. For some
professionals, however, their views were combined with the overall positive view of
timber construction and a desire to learn more.
When the respondents were asked if they were educated about timber-frame
construction at school the data were obtained and recorded in Figure 19. As can be seen
in Figure 19 below, only 50% of the building professionals who took part in completing
72
the questionnaires were educated about timber-frame construction. This is not a
surprising finding, considering that most houses are built from brick and mortar in South
Africa.
The building professionals were asked if South Africa has enough skilled workers for the
construction of timber-frame houses. Sixty-two point five percent (62.5%) think South
Africa does not have sufficient skilled labourers to construct timber-frame houses. This is
evident in the fewer numbers of carpenters compared to bricklayers in South Africa.
None of the participants think that there is enough plantation forests in South Africa.
However 30% mentioned that there is enough land for plantations, if the demand is there.
Figure 19 below illustrates clearly that, 15 out of the 24 respondents (62.5%) said South
Africa does not possess enough skilled people for the erection of wood-frame dwellings.
On the other hand, 37.5 % said that the country has enough skills. This finding shows
how unskilled South Africans regard timber-frame construction and illustrates that
perhaps efforts to educate or provide more training needs to be increased.
Seventy-five percent of the personnel do not have any idea whether South African banks
finance this type of construction. They argued that the banks always give bonds for brick
houses and not timber houses. Even the developers are not doing enough to market
timber-frame houses and 25% of the respondents were of the opinion that banks do, in
fact, finance timber-frame housing. They pointed to the many timber-frame lodges and
cabins in the country. They all believed that the insurance would be higher for timber-
frame than masonry houses because timbers are prone to fire, fungus and insects. They
also mentioned that timber-frame houses would deteriorate faster if there are not treated
and given proper care.
Based on the Figure 19 below, it can safely be concluded that the building professionals
do not know that South African banks finance wood-frame structures and 75% of the
respondents indicated that they do not have any idea if SA banks give loans to people
who build timber-frame homes. Conversely, 25% indicated that there is finance for wood-
frame houses. This is alarming and shows that not enough is being done to promote this
alternative method of construction. They all agree that wood houses are more
aesthetically pleasing and demonstrate a timeless elegance and durability, as well as the
way timber lends itself to craftsmanship. They would all like to stay in these buildings if
they were structurally sound and given enough treatment for fungus and insects.
73
When the respondents were asked if the timber-frame method of construction could be
used in ROP houses or could replace bricks as a type of material for houses in any South
African location, the following data were obtained: Fifty percent of the participants are not
convinced that timber-frame construction can be used for ROP houses or for any house
for that matter. They all agreed that the majority of low income households would be
susceptible to fire during cold weather which can be dangerous to the houses. Most ROP
houses accommodate more than 5 people and they would deteriorate due, to excess
moisture (bath rooms) affecting the life span of the houses. They argued that timber-
frame houses are high maintenance and have a short life span. This would bring more
problems than solutions to homeowners.
Figure 19 below shows clearly that 50% of the respondents would not consider using
wood walls instead of brick walls for ROP houses. Nonetheless, 50% think it is an
appropriate method. Based on the information above, one can conclude that the timber-
frame house has a chance in the South African market if it performs well structurally and
if professionals are eager to accept it.
Responses according to the building professionals are summarised in Table 10 and
Figure 19 below.
Table 10: Responses from building professionals
Professionals Ves No Total Percentage Percentage
I I I Ives 1No
timber education 12 12 24 50% 50%
enough skills
19 I15 124 r37.5% 62.5%
finance from banks 6 18 24 25% 75%
timber frames for 12 12 24 50% 50%
ROP house
74
Professionals Responses (Total=24)
20
18
!rJ:: 16
Cl)
"c&. 14
-CC..l)l). 120 10
Ó
Z 8
6
4
2
0
timber education enough skills finance from banks timber frames for rdp
Questions
Figure 19: A bar chart showing responses from professionals
8.4 Questionnaires to the general public
Eighty-eight point twenty-four percent (88.24 %) of the general public have seen timber-
frame houses previously. All the people think that they would not be suitable for RDP
houses. Most of them, (70%) think that wood construction can be used only for cabins for
guards, for shacks or for small storage houses. Fire and decay are the main concern.
They all argued that wood is naturally consumed by fire and its use as fuel and as a
source of charcoal is well known.
Figure 20 below shows clearly that the majority of the respondents (88.24%) are familiar
with wood-frame dwellings, whereas only 11.76% seemed not to have seen the
structures previously. This suggests that timber-frame construction is not a new method
of building and a few houses built with timber can be seen throughout South Africa.
Twenty-eight percent (28%) of the participants think that this alternative wall construction
method would be accepted for low income buildings in South Africa. Poor sound
acoustics was mentioned as one of disadvantages of wood. They maintained that timber
75
floors are very noisy. Some people believe that timber-frame walls cannot be renovated
as easily as masonry walls which can be effortlessly renovated with a new coat of paint.
The bar chart (Figure 20) below indicates that 76.47% do not agree that timber-frame
homes would be accepted by the South African public. Therefore, one can conclude that
the general public will not give wood-frame construction a chance in the erection of their
homes. Forty-seven percent said they would stay in timber-frame houses if the
opportunity availed itself, while 52.94% said they were afraid they might burn while living
in them. Furthermore, they all believe that the timber-frame method of construction would
deplete all the forests in the country.
The results demonstrate that 52.94% would not stay in timber-frame homes, while
47.06% would. Based on Table 11 below, it shows that the majority confirmed that they
do not trust wood-frame houses.
Responses according to the general public are summarised in Table 11 and Figure 20
below:
Table 11: Responses from the general public
General Public Ives No ITotal IPercentage IPercentage
Ves No
Have seen timber house 15 2 17 88.24% 11.76%
Timber house accepted by 4 17 ]23.53% 176 47]13 . %
public 1 1
Would stay in timber house 8 9 1~ 47.06% 52.94%
76
General Public Responses (Total=17)
:el
Cl> 14
'1:1
c:
o 12
Cl.
UI
Cl>
0::: 10
'0
o 8z
6
4
2
Have seen timber horse timber house accepted by Can stay in timber house
public
Questions
Figure 20: General public responses
8.5 Interviews to two contractors
Two contractors from two small construction companies were interviewed. The first
contractor (Mr Thulane Baloyi) has a slight idea of how timber-frame construction works.
The second contractor (Mr Peter Tshabalala) has seen timber-frame houses before but is
not familiar with this alternative wall system. The two were quite interested to learn about
timber-frame construction.
Mr Tshabalala said if wood construction can benefit homeowners he will be more
interested to use it as an alternative wall system for ROP houses. Time and cost are
major factors in the construction of any building. As a result both contractors were
satisfied to discover that timber-frame construction can save time and money if used
correctly. They agreed that if the government introduced a timber wall system they would
embrace it without hesitation. They said not much of work is being done to promote
timber-frame construction and that might be why there is little known about it.
77
8.6 Conclusion
Most of the participants who completed the questionnaires were not convinced that
timber-frame walls can replace traditional brick and mortar walls in the construction of
ROP houses in South Africa. Even though an explanation of how timber-frame
construction works was given, people, especially the general public remain sceptical
about timber-frame construction. The general public have not yet accepted timber-frame
construction as they are afraid of change. As result, it is not going to be easy to
implement. More training is encouraged for all building stakeholders and ordinary people
to learn more about timber-frame so that they will be able to give fair criticism.
78
CHAPTER 9
9 CONCLUSIONS AND RECOMMENDATIONS
9.1 Introduction
As discussed in Chapter one of this research report, the aim of this study is to determine
whether masonry, being the most used material in residential housing construction in
South Africa, can be replaced by timber-frame construction on ROP houses to improve
the quality and durability of houses, on the other hand, while saving time and money.
Furthermore, the objective is to point out and analyse the effectiveness of using the
timber-frame system.
9.2 Conclusion
There are possibilities that timber-frame structures can become common and competitive
in South Africa. The fact that there are houses spotted all over the country makes it clear
that timber-frame construction is effective if used according to National Building
Regulations standards.
In the study timber-frame and brick and mortar walls were compared. The two methods
of construction mainly differ regarding walls, as other building elements such as the
foundation, roof, doors and windows remain the same. The comparison was done to see
which of these methods performed better in certain areas such as durability and
structural, acoustic and thermal performance. The most effective, efficient and economic
method will be used as an alternative to traditional brick and mortar which has been used
to build low income (ROP) houses in South Africa.
The alternative wall construction method was analysed. Preference will be given to the
wall system which will reduce waste, reduce the amount of materials required, and
simplify assembly and increase accuracy and speed of construction. Timber-frame walls
were shown to be as competitive as brick walls and were a much better option in terms of
time. The less time spent on building a house, the less expensive it is. The time spent
constructing a timber-frame home is far less than for a brick building. This can be
beneficial to the government for increasing the percentages of ROP houses built per
year. Materials for two wall systems were discussed since no house can be built without
79
the fundamental knowledge of building materials. It was recognised that a timber-frame
wall requires many different materials for the wall to be substantial.
The difference between conventional masonry and timber-frame was emphasised.
Timber-frame houses are erected by carpenters whereas brick houses are built by
bricklayers. Other features for the erection of houses such as foundations, windows,
doors and roofs remain the same for both systems. The advantages and properties of
timber-frame houses were discussed. There are many reasons why timber is an ideal
construction material. It is renewable, durable and a good insulator - warm in winter and
cool in summer. From this section it is clear that wood-framed houses are as competent
like brick or block houses. Stakeholders in the building industry should take note of the
importance of using timber-frame.
The RDP was explained, along with all the materials that are used for construction of its
houses. The buildings are usually simple structures and erected with bricks or blocks.
Even though the South African government is doing all it can to provide people who need
shelter, there are still lot of people on the waiting list. The slow delivery of RDP houses
causes a backlog which needs to be solved. Timber-frame construction, because of its
quick erection, can speed up the delivery process if given a chance.
Emphasis was placed on the cost implications. Timber-frame construction proved to be
more expensive than brick walls. The hypothesis that timber-frame is more cost effective
than masonry brick walls was therefore not achieved. However, timber-frame wall
construction seemed to be cheaper than other form of construction such as steel-frame.
This was verified by Kothmann's case study. The advantages of timber-frame buildings
and the differences between conventional building methods and timber-frames were also
compared to highlight the effectiveness of timber frames.
Timber-frame housing construction in South Africa is not yet as popular as masonry brick
walls, although further investigation on this needs to be conducted. A survey consisting
of questionnaires and interviews was done to determine whether the alternative wall
construction method is known and would be accepted by the general public and building
professionals. The results indicate that the majority of people do not really understand
and are not aware of the benefits of using timber-frame construction. It might be that
insufficient education or training was given to the building specialists about this
alternative method of construction. This might be why most people think South Africa
does not possess the skill to erect wood-frame dwellings. The construction industry in
80
South Africa needs to encourage more institutional knowledge in timber-frames, because
lack of background knowledge of the material makes it difficult for building disciplines to
encourage the use of it. In addition to these an alarming percentage of the participants
had no idea that they can get loans to build timber-frame houses, as well as insurance. It
is clear that not enough is being done to promote the timber market.
Timber-frame was found unsuitable to use as building material for ROP houses. It is
perceived to pose a greater risk of fire than any other form of construction material. It is
also costly as timber-frame needs to be treated and maintained in order to have a long
lifespan. This is true because for any building to survive measures should be taken to
improve the life-cycle of building and preserve its original status. This is the same for
masonry brick walls that require plaster and paint to withstand the test of time. As with
any mortgage, insurance is provided for wood-frames to guard against any disaster.
Social perceptions and attitudes about timber-frame housing have a negative influence
on its use. More awareness about this construction method is still needed and its use
needs to be promoted.
The goal of this study was to determine whether timber-frame walls can replace
traditional brick and mortar walls to improve quality, facilitate faster construction solutions
and durability, while at the same time being cost effective. Will timber-frame wall
construction be a better alternative to brick and mortar wall construction in South Africa?
And can timber-frame wall construction be appropriate for ROP houses? The problem
was partially solved because brick and mortar walls were demonstrated to still be the
better option for ROP houses in terms of cost, maintenance and durability. Brick
performed better in water resistance, thermal performance, acoustics and structural
strength. In terms of the speed of construction, environmental sustainability and
aesthetics, timber-frame is still a method of construction to be reckoned with.
9.3 Recommendations
It is recommended that other forms of wall construction such as steel-frame and poly-
blocks should be explored to find the less costly method than masonry brick walls. Since
most building professionals were not educated about timber-frame, the South African
government should focus on developing further training courses for architects, quantity
surveyors, developers, engineers, technical inspectors and contractors about the
construction of timber-frames. The full advantages of timber-frame technology will be
81
experienced only when professionals themselves become more familiar with it through
education.
82
Appendix A
Questionnaire
T~MBIER-lFRAMIEWAllS AS Al rIERNAr~VIE TO BR~CK
WAllS CONSTRUCr~ON
QUESTIONNAIRE
JULY 2012
83
QUESTIONNAIRE
INTRODUCTION
Timber framing is the method of creating a house using heavy timbers jointed together
with mortise and tenon. This questionnaire is aimed at determining the perceptions of
people in South Africa about using timber-frame as alternative to brick or block walls on
RDP houses. The figure below shows a house erected with timber.
Figure 21: Timber-frame house (Timber Frame Builders Association, 2009)
Kindly complete the questionnaire carefully and send it to the details below:
To:
Attention: Maneo Mabesa
Fax: 036 342 3114
E-Mail: maneom@gmail.co.za
NOTE: THE QUESTIONNAIRE CONSIST OF SECTION A & SECTION B
BOTH SECTIONS MUST BE COMPLETED BY ALL PARTICIPANTS
THANK YOU
84
APPENDIX A:
QUESTIONNAIRE - TIMBER-FRAME WALLS AS ALTERNATIVE TO BRICK
WALLS CONSTRUCTION.
SECTION A
BACKGROUND
1. Firm/Company Location
2. Professional Affiliation (Architect, Engineer, Contractor/Builder, Developer, Other)
3. Qualification Obtained
4. Gender
5. Ethnicity
SECTION B
TIMBER-FRAME WALLS
1. How familiar are you with timber-frame residential houses?
2. How much influence do you have over design and specification decisions?
3. If you received professional schooling, to what extent were you educated about
timber-frame construction issues during your degree or training program?
4. Do you think South Africa has enough skill for construction of timber-frame
houses?
5. Do you think South Africa has enough forest to use for construction of timber-frame
houses?
6. Are there any banks in South Africa that finance timber-frame houses?
7. Will insurance be higher on a timber-frame house than on a masonry house?
85
8. Do you think timber-frames can replace bricks as a type of materials for houses in
any South African's location?
9. Do you think timber-frame house is more attractive than masonry house?
10. Would you live in a house built with these construction methods if you had the
opportunity to do so?
11. Do you think this type of construction can be used in RDP houses?
12. Do you think timber-frame houses are high maintenance than masonry houses?
13. Do you think timber-frame building cost more than masonry building?
14. Would you consider buying a house constructed with these construction
methods?
15. Do you think a life span of timber-frame houses same as masonry houses?
16. Do you think this type of houses will be accepted by the general public?
86
APPENDIX B:
INTERVIEW QUESTIONS
TIMBER-FRAME WALLS AS ALTERNATIVE TO BRICK WALLS CONSTRUCTION.
1. How long have you been in the construction industry?
2. Do you have experience in the construction of RDP houses?
3. How many houses have you build so far?
4. Do you have experience in timber-framing?
5. Do you have any idea how timber-framing works?
6. Have you seen a timber-frame house before?
7. Which method of construction is faster between masonry brick and timber-frame
walls?
8. Do you think timber-frame wall can replace brick and mortar wall in the construction of
RDP houses?
9. Which method is cheaper between timber-frame and brick wall construction?
10. Do you think timber-frame house is more attractive than masonry house?
11. If the South African government propose to use timber-frame as alternative to
masonry brick wall will you accept?
12. Would it be possible for you to learn and adapt easily to this alternative walls?
87
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93
Appendix C
A HOUSE PLAN
94
I WINDOW SCHEDULE III ..........,rES I
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width 533 mm !,.=:.~::..~..-=~-.:~=-_=:=~---:[8] -height 949 mm !..-=.::-?---E=_::-:=:~=.._'.=. .:--=North Elevation East Elevation .._. .._=.-. :Sc!ie 1:100 Sc!ie 1:100 NCT1S ...__ ...._--_
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