Sustainable construstion module: Read and Interpret Construction Drawings & specifications

1. Unit Standard 140414: Read and interpret construction drawings and
specifications. 3 credits
A drawing is one of the most effective tools we can use to communicate with. It
holds no barriers between people who do not understand each others language. It
is a method used to communicate and share ideas with people of different
cultures and nationalities. Ancient rock art drawings found in caves around the
world describes the way in which people lived in those years.
Explaining to a person how to build a cupboard will be near impossible whereas
a drawing will take but a few minutes.
The ability to read and interpret construction drawings is of great value to any
construction worker. He will be able to accurately construct an architect’s
architectural concept and design into a realistic building structure. Construction
drawings uses lines, words, symbols, abbreviations and specifications to indicate
to the construction team what the building will look like and the purpose and use
thereof. In this unit standard we aim to describe to you in detail how
Construction drawings are read and interpreted.
A/W graphic
Specific Outcomes
We will work towards achieving the following Specific Outcomes in this chapter:
1 Explain the role of drawings and specifications.
2 Identify drawings and symbols used on a construction drawing.
3 Apply information from drawings in construction activities.

2. 4 Interpret specifications appearing on construction drawings.

3. UNIT 1 EXPLAIN THE ROLE OF DRAWINGS AND
SPECIFICATIONS.
By the end of this unit you should be able to:
• Explain the role of drawings in relation to project specifications, contract
documentation, quantities and construction. (SO1 AC1)
• Explain the role of specifications in relation to quantities, quality of work,
contract documentation and payment to contractors. (SO1 AC2)
1. The role of drawings (SO1 AC1)
The role of the drawings is to show the graphical outlay of a building to be
constructed. These drawings or plans consist mainly of lines and symbols that
are drawn to a precise scaled measurement to represent the actual building.
Buildings are structures which are planned and designed by professional
architects, drawn by draughts­persons and built by building contractors. There
are also many other role players who will interact with the drawings during the
course of the construction.
Something to know
Ninety–nine percent of all building plans are drawn on computer using a
computer aided draughting package. Some of the most commonly used programs
are Allycad, Autocad and Caddie.
A building project starts with an owner who intends to erect a building; this
could range from a simple house to a shopping mall or school or even multi­
storey buildings. Buildings are not all of the same design and size and it is not
common to find two buildings which are exactly the same. It is only in situations
of housing estates where we will find houses that are of the same design.
Buildings are designed to satisfy the specific needs of an owner or more
specifically the client. The complexity of a building structure requires that a fully
detailed set of documents, which clearly spells out a complete detailed
description of the work that needs to be done.
In order for this be fully understood by the building contractor, the job of the
architect will be to specify each part or section of the construction in full detail.
It will be totally impossible for an architect to describe the design of a building in
words. Architects will therefore produce fully detailed drawings together with a
set of specifications that will be used by the contractor to erect the building.

4. Let’s now take a closer look at some of the important documents that will be
required: The complexity of the design requires a fully detailed description of the
work that needs to be done.
The contract drawings: Many of us know these as the “plans”. The drawings
represent a pictorial overview of the proposed building. It consists of lines,
symbols, dimensions, levels and many other graphical features of the building.
We will discuss the role of the drawings in more detail in a later chapter.
The specifications: Specifications can mostly be described as that which cannot
be drawn. The specifications will either be written on the drawing or it will be
compiled and an additional set of notes. Specifications must be written clearly
and in simple language. Words or descriptions, such as,”best” quality or “highest”
quality or “proper” workmanship are cause for confusion. Two of the most
common specifications include:
General specifications which contain the workmanship and materials, and
Project specifications cover the workmanship and quality of the materials that
are unique to a specific project. Project specifications will always take preference
over the general specifications.
The Bill of Quantities: The purpose of the bill of quantities is to list all the
materials and labour operations necessary to construct a building, together with
a measurement of the quantities of materials and work involved. This document
is used by the contractors to tender for a contract. A fully priced bill constitutes
the contractor’s offer to undertake the work at that price. The bill of quantities is
drawn up by a professional quantity surveyor.
The conditions of the contract: This will define the liabilities, responsibilities and
powers of the employer, contractor and architect. It would include methods of
payment, insurance, liability of parties to the contract.
The tender: This is a signed financial offer of the contractor to construct the
works.
The legal deed: This document is signed by both parties confirming their
respective intention to have contract between them as defined by all the above
documents.
All these documents together will be known as the contract documents.

5. {Important words and ideas}
Specifications: Is a description of the quality of work and materials for a
particular job, written in a sequence of trades prepared to explain those things
concerning a project which cannot be shown on a drawing,
Its main purpose would be to define the products to be used, the quality of the
work, any performance requirements and the conditions under which the work is
to be executed.
Contract documentation: The contract documentation is a legal contract
which consists of the drawings, the specification, the bill of quantities or
schedule of prices, the general conditions of the contract and a legal deed which
binds the contractor and the client.
Sequence of trades: The order in which the various building and service trades
carry out their work in a new building. This is the order in which the trade
sections occur in a bill of quantities or specification.
Bill of quantities: A complete list of the materials and labour operations
necessary to construct a building, together with a measurement of the quantities
of materials and work involved. This document forms the basis of the contractor’s
tender and each item is priced by the contractor by inserting the rate against
each item and multiplying it by the quantity. A fully priced bill constitutes the
contractor’s offer to undertake the work at that price.
Quantities: The amounts of building material or building operations needed to
construct a building which is written in the bill of quantities.
Quality of work: The inspection methods implemented on a building site to
ensure that a product maintains accepted minimum standards of quality.
{End}
Activity 1.1
1. Explain, with no drawings or sketches, where you live.
2. State the difference between general and project specifications.
3. State the difference between quantities and quality of work.
4. What is meant by contract documentation?

6. 5. What is meant by a tender and a legal deed?
2. The role of the specifications (SO1 AC2)
The purpose of the specifications is to describe in detail the type of materials to
be used; the specifications complement the drawings. Builders will not be able to
what type and grade of materials will be required if there are no specifications.
The quantity of materials and quality of work will all be contained within the
specifications.
Quantities: As we explained earlier there are no two buildings that are exactly
the same. It stands to reason that the quantity of materials will then also differ.
The builder will need to know how much materials he will need to complete the
proposed building before he can do his costing and complete his tender. This
information is contained within the bill of quantities which consist of an itemised
list all the materials that will be required to complete the job.
The quality of work: This is one of the main purposes of the specifications and
has a direct link towards the type of materials to be used. The methods he may
or may not use in order to construct the building. It will give a clear description
of the materials, example, the type of sand for the concrete must be well graded
river sand or all the brick joints must be grouted with mortar with no openings
between the brick joints.
Contract documentation: These would include the conditions of the contract and
will address issues concerning the:
• The extent of the work to be done
• The start and completion dates of the contract
• Access to the site
• Arrangements for the storing of materials
• Temporary services on site in the form of water connection, electricity and
toilets.
• The health and safety of the workers as well as the general public
These are but a few although there could be many more issues which be
considered.
Payment to contractors
A building contractor is paid for work completed and is never paid in advance.
These payments are known as interim payments. In huge projects payments will

7. be done on a monthly basis, whereas in smaller projects payments are done
during the different stages as building progresses. These stages would be agreed
upon by the architect and builder when the contract is signed. The payment or
certificate will state the work that was completed and the materials that were
used. A typical payment plan for a normal house would be:
• At the completion of the foundation up to floor level;
• The superstructure up to the roof level;
• When the roof is completed;
• At the completion of the house
• The final payment will be when all defects are completed.
Activity 1.2
1. Which important points must be considered in the conditions of contract?
2. What is the purpose of the specifications?
3. At what stages of a contract will the building contractor be paid?

8. UNIT 2 IDENTIFY DRAWINGS AND SYMBOLS USED ON A
CONSTRUCTION DRAWING
By the end of this unit you should be able to:
• Identify drawings in terms of type and application for a construction
process. (SO2 AC1)
• Explain the key functions of the drawing in terms of the finished product.
(SO2 AC2)
• Identify the key users of the drawing in terms of work responsibility. (SO2
AC3)
• Interpret symbols and abbreviations in terms of their functions and
meanings (SO2 AC4)
• Interpret the layout in terms of the different views shown (SO2 AC5)
• Explain the purpose of each view in terms of the result of the end product
(SO2 AC6)
1 The different types of drawings and their applications. (SO2 AC1)
It would not be possible to give a builder a written description how to construct a
building. The construction of any building would require a complete set of
drawings that would show all the aspects and outlay of a proposed building.
These drawings are commonly referred to as the construction drawings, building
plan or plan.
Buildings are designed by professional architects who employ the services of
draughts­persons to draw the working drawings for a project. The draughts­
person must ensure that he conveys the architects design correctly and
accurately to the builder and in doing so he must ensure that he includes all the
necessary information on the plan for the successful completion of the building.
A construction drawing for a single­storey house would consist of the following
drawings:
• A site plan
• A plan view of the floor layout
• Sectional views
• Elevations
• Schematic layout of the sewage plan
• Details
Each of these drawings would be accompanied with all dimensions, notes and
labels. The builder must be provided with all the required information to
construct the house. Supposing the house has an additional floor above, that is, a

9. double­storey house, then there will have to plans for the reinforced concrete
floor and staircase. These are plans that are prepared by a professional civil
engineer and would include:
• A steel reinforcement layout plan for the floor and staircase
• A schedule that would show the sizes and shapes of the reinforcing steel.
2 The key functions of the drawing in terms of the finished product. (SO2 AC2)
The key function of the drawings is that it must be clear, easy to read. The
drawings must consist of sufficient plan lay­outs, sections and elevations,
together with details for special parts of the construction. The drawings must be
neatly drawn; with all dimensions, notes and specifications clearly stated. It
must have a clear indication what the finished building will look like. The
construction team must be able to understand the purpose of the building. There
must be no uncertainty which will confuse the builders. Buildings are designed
as fit for purpose for its intended use. The building must be erected to the correct
specifications as designed by the architect. Changes to the original design can
only be affected by the owner via the architect. The owner or the builder is not
allowed to make any changes without consulting the architect.
3 The key users of the drawings (SO2 AC3)
Before and during the construction the plans will be used by various people who
are either directly or indirectly involved with the construction of the building.
It might be worth mentioning at this stage that many months would pass
between the drawing of the plans and the building being constructed. The reason
for this is that the plan will go through many stages before final approval is
granted for the building to be erected. This approval starts with the client or
owner approving the design and cost of the building and then there are the many
divisions within the local authority approving the construction methods.
Once the drawings are approved and a building contractor is appointed, the
contractor will then use the drawings to calculate and order the required
building materials. Copies of the drawings are also sent to companies who
specialize in certain parts of the construction, these companies are called sub­
contractors. Examples of sub­contracting companies are plumbing, electrical and
painting companies.
A copy of the plan can also be sent to a roofing company to prepare the roof
trusses.

10. Something to know
The building contractor is also known as the main contractor.
Sub­contractors are either nominated by the architect or owner or they are
contracted by the main contractor.
A plumbing company will supply the new building with its own water supply;
install the bathroom fitments and fittings as well as the hot­water cylinder and
kitchen sink. They also construct the underground sewer drainage system.
An electrical company will supply the building with electricity, either by solar
panels or cables, light fittings, power plugs and connect the hot­water cylinder to
the power supply.
The building contractor’s on­site representative, known as the general foreman,
will first use the plans to locate the plot or site where the building is to be
constructed, then to prepare the site ready for building by:
• Setting up the temporary site structures, such as, sheds for storing
materials, office, toilets and temporary water supply.
• Setting up a suitable position for the concrete mixer
• Identifying storage areas for bricks, sand and stone.
• Identifying access for delivery vehicles without disrupting the general flow
of vehicular traffic
• Setting up security fencing to protect the general public
Once the site has been cleaned the plans will be used to:
• Set out the position of the building
• Establish the levels and heights of the building
Activity 2.1
1. Who draws the workings drawings for a building project?
2. Which parts of the building must a civil engineer prepare drawing for?
3. Name three examples on a building site where sub­contractors are used.
4. Which parts of the drawing would be of interest to a plumber?
5. Who represents the building contractor on a building site?
6. What important preparations must be established before the actual
construction commences?
4. Abbreviations and symbols (SO2 AC4)

11. The use of symbols and abbreviations is used to prevent “overcrowding” the
drawing with too many words. Symbols are simple line drawings or graphics that
would represent either the various types of materials or fixtures and fittings or
services. Symbols are also accompanied by abbreviations. The lines that makes
up the drawings are also symbols; with each line representing a feature of the
building. Abbreviations normally takes the form of the shortened version of the
full word, examples of these are:
• The letter “B” on a plan would indicate the position of the bath in the
bathroom.
• “CONC” would be the abbreviation for concrete.
Tables 1 below shows some of the abbreviations that are commonly used on
building plans. A complete list of all abbreviations and symbols are given in the
latest SANS Code of Practice on Building Drawing Practice.
Components/Material Symbol Components/Material Symbol
Air brick AB Invert level IL
Aluminium AL Manhole MH
Asphalt ASPH Not to scale NTS
Bidet BT
Bitumen BIT
Overall OA
Brickwork BWK Pressed metal PM
Cast iron CI Polyethylene PE
Cleaning eye CE Rodding eye RE or AE
Concrete CONC Shower 30 SH
Copper COP Sink S
Column COL Soil pipe SP
Cover level CL Standpipe STP
Damp-proof course DPC Storm water drain SWD
Damp-proof membrane DPM Storm water channel SC
Drawing DRG Stormwater pipe SWP
Fibre cement FC Top T
Galvanized steel GALVS Unplasticized polyvinyl
uPVC
Granolithic GRANO chloride
Hardcore HC Urinal 40 U
Hardwood HWD Vent or ventilation pipe VP
Inspection chamber IC Wash basin WB
Wash trough WT
Inspection eye IE Waste pipe WP
WC pan (water closet) WC
TABLE 1

12. The following tables are extracts from SANS Code of Practice on Building Drawing
which shows some of the symbols most commonly used on construction drawings.
Table 2 below shows how materials are represented.
Undisturbed earth Undressed wood
Earth fill Dressed wood
Hardcore Common brick
Stone concrete Face brick
Sand plaster or screed Sheet membrane
Table 2
The symbols in Table 3 are known as general graphical symbols. That are used
to show specific parts on a construction drawings
GENERAL SYMBOLS SERVICES FIXTURES AND FITTINGS
Description Symbol Description Symbol Description Symbol
Centre line Drain Bath
D Gully Wash-basin
Datum line
Diameter Hot water Water-closet pan
cylinder (toilet)
WW
Finished floor 0,000 Storm water
Shower
level drain
North point Water meter Kitchen sink
1:2
Ramp
Direction of the the arrow
must always point up the ramp
Staircase
Direction of the the arrow must
always point up the staircase

13. Table 3
5. The layout is interpreted of the different views shown (SO2 AC5)
The purpose of each view in terms of the result of the end product (SO2 AC6)
Designers must supply the builders with all the information required to
successfully erect and complete a building. This is done by presenting a proposed
building in the form of a graphical layout which will consist of various types of
drawings. The layout drawings are also commonly referred to as the construction
drawings or building plan. A builder uses the layout drawings to interpret the
designer’s idea into reality. All drawings must be fully dimensioned and labelled
with all notes and specifications.
The title panel
Each drawing must consist of a title panel. This panel is situated at the bottom
right­hand corner of the drawing page and contains a summary of the
information of the drawings on the page. A typical title panel for a normal house
will read as follows and assuming it’s a new house:
New house for Mr and Mrs John Andrew Mazibuku on erf 227,
Carrington Street, Village Green Estate, Kensington, Kimberley.
Signed: …………………………………………..
This signifies to the builder where the house is to be erected. The address will
also be shown on the site plan. The information of the draughts­person must also
be included in the title panel.
Drawn by:
Mrs J.B. Sitholy, Suite 105, The Waterfall,
Battlefield Drive, Kimberley.
Signed……………………………….
Other information would include:

14. • The north point
• The date the drawing was completed.
• The applicable notes relating to the drawing.
A typical title panel is shown in figure 2.1 below:

15. NOTES:
New house for:
Mr and Mrs John Andrew Mazibuku
on erf 227, Carrington Street,
Village Green Estate,
Kensington, Kimberley.
Signed: .......................
Drawn by:
Mrs J.B. Sitholy, Suite 105,
The Waterfall,
Battlefield Drive,
Kimberley.
Signed:...............
Date: 15 April 2005
Figure 2.1
A typical set of layout drawings will consist of:
1. Locality drawings: Identifies and locates the site from a town plan.
2. Site plan: The site plan is normally situated on the bottom right­hand
corner of the drawing page, next to the title block. Figure 2.2 below shows
an example of a site plan. This is the first drawing which the builder
inspects and extracts the following information from the site plan:
• The position of the boundary pegs;
• The dimensions of the site;
• The location of the proposed building;
• The dimensioned position of the building line;
• The position of true north;
• The registered number of the site;
• Excess to the site;
• The positions of the any drains, storm water channels and sewer
lines;

16. Boundary Peg Boundary Peg
Back Boundary 15,00
20,00
ERF 227
2 500
Side Boundary
Side Boundary
Proposed
new
dwelling
Front building
line
3 000
Site access
30 metres to
Brickfield Road
Front Boundary
Boundary Boundary
Peg CARRINGTON STREET Peg
Figure 2.2
3. The plan layout of the building: This is the horizontal or top view of the
building which also shows the shape of the building. A double storey
building will have two plan layouts. Figure 2.3 below shows a typical plan
layout for a single house. The following information will be provided:
• The dimension of the building which will include the overall size of the
building, the thickness of the walls, the sizes of rooms;
• The designations of the rooms, example, bedroom, bathroom, kitchen;
• The positions of the doors, windows and openings;
• The plumbing layout of the bathroom and kitchen;
• The floor levels;
• The floor finishes, example, tiles, carpet, timber;
• The positions of any fixed furniture, example, bedroom and kitchen
cupboards .

17. A
11 060
270 3 500 110 3 000 110 3 800 270
270
270
ND 10F ND 10F ND 1 ND 1
BEDROOM 2
3 000
BEDROOM 1 LIVING ROOM
CARPET CARPET CARPET
ND 22
7 100
110
110
7 100
900
900
ND 1
110
3 450
TABLE TOP
BEDROOM 3 KITCHEN
1 870
CARPET CERAMIC TILES DINING ROOM
BATH
2 360
CERAMIC TILES
ND 1
TILES
600
ND 10F NC10F
270
NC2F ND 10
270
600
110
A 110
110
270 2 445 1 945 3 000 2 800 270
PLAN VIEW
Figure 2.3
4. Sectional views: This is a vertical section which shows a “cut­through”
view which would indicate the following:
• The dimensions and position of the concrete foundations;
• The height of the foundation wall, not less than 4 brick courses below
ground level;
• The position of the natural ground level (NGL);
• The position of the damp proof course (DPC), minimum 150 mm above the
natural ground level;
• The thickness of the concrete floor;
• The height of the external walls from the finish floor level to the
underside of the wall plate;
• The finishes to applied to the walls;
• The heights of the door and window frames;
• The pattern and pitch of the roof truss;
• The overhang of the roof truss;
• The fascia board and gutter;
• The description of the roof covering;
• The description of the ceiling;

18. • All the notes and specifications pertaining to the sectional view;
Figure 2.4 shows a typical sectional view through one of the eaves.
ROOF CONSTRUCTION
Rationally designed roof trusses
Fibre cement sheeting on manufactured by approved
75 x 50 purlins at 900 centres timber roof company
Pitch 22º
Ø75 half round
Roof overhang 300 mm gutters
6 mm skimmed rhinoboard on
38 x 38 brandering at 400 centres
75 mm cove cornice
Bedroom 1
Plaster
2 400
Bedroom 3
Plaster
DPC
DPC
NGL 25 mm screed on 75 mm concrete NGL
600 X 200
on 250 micron damp proof membrane
on well compacted clean sand filling
600 X 200 600 X 200
SECTION A-A
IBR roof sheeting on
75 x 50 purlins at 900 c/c
114 x 38 All truss
Wall plate members
Roof pitch 114 x 38
22º
100 x 75 6 mm rhino board on
gutter 38 x 38 brandering at
Roof
top 4 courses of 400 c/c
Overhang cavity wall built 75 mm cove cornice
solid
dia 75 plastic
swan neck
19 mm Plaster
dia. 75 mm Wall tie
Down pipe (Tie wire)
DPC
25 mm Screed
Down pipe Concrete floor
shoe slab
Natural ground level DPM
Earth undisturbed
Cavity below damp proof
Earth fill course filled with concrete
600 x 200 Concrete foundation

19. Figure 2.4
5. Elevations: Elevation drawings would normally consist of four drawings
which would show the outside views of the house. Each view being
orientated towards the four points of a compass, as shown in figure 2.5
below, that is, north, south, east and west. The purpose of the elevations
are as follows:
• The outside height of the building to show the floor level in relation to the
ground level;
• The height and shape of the roof;
• The fascia board, gutters and down­pipe;
• The position and heights of all the doors, windows, steps and sills;
• Applied finishes to the walls
Fibre cement sheeting
Plaster
Down
pipe Plaster
NORTH VIEW
EAST VIEW
Fibre cement sheeting
Plaster
Down
Plaster pipe
SOUTH VIEW WEST VIEW

20. Figure 2.5
Activity 2.2
1. State the difference between abbreviations and symbols.
2. Why are abbreviations and symbols said to be important on construction
drawings?
3. Draw neat freehand drawings of the following symbols:
Concrete; face bricks; hardcore.
4. State the difference between a locality plan and a site plan.
5. What information will a builder extract from the site plan?
6. What is the purpose of the plan view of a construction drawing?
7. What information will a builder extract from the elevation drawings?
8. The abbreviations “DPC” and “DPM” appear on a drawing.
8.1 What do these abbreviations mean?
8.2 Where on a drawing would these abbreviations appear?
8.3 State the importance of the DPC and DPM.
8.4 What is the required thickness of the DPC and DPM?
8.5 State the minimum height of the DPC.

21. UNIT 3 APPLY INFORMATION FROM DRAWINGS IN
CONSTRUCTION ACTIVITIES
By the end of this unit you should be able to:
1. Drawings are orientated in terms of site landmarks and the north
indicator. (SO3 AC1)
2. Information is extracted from the drawings in terms of the setting out
requirements on site. (SO3 AC2).
3. Scales are interpreted and measurements converted in terms of actual
dimensions required. (SO3 AC3)
4. Dimensions are interpreted from the drawings in terms of site
requirements. (SO3 AC4)
1. Drawings are orientated in terms of site landmarks and the north
indicator. (SO3 AC1)
South Africa receives all of its sunlight from the north and that is what brings
warmth into our homes. It is compulsory for all building plans to have a north
indicator. Designers therefore orientate the building to such a degree that most
of the building will benefit from the warm rays of the sun, as shown in figure 3.1
below. We will soon be able to harvest (collect) and store this energy and use it to
warm our homes against the cold nights. We will have more and more houses
fitted with solar heating cells that will heat our hot­water cylinders; the new
road signs are also being equipped with solar panels to supply energy to light up
road signs.
You will be able to find the position of north if you stand in a position with your
right shoulder pointing in the direction where the sun rises (east) and your left
shoulder pointing in the direction where the sun sets (west). You will then be
facing north. This will however not be an accurate method of finding true north,
but it should give you a general idea which way north is. We use a compass to
find the exact direction of north.

22. sun
of the
Angle
H
RT
NO t
s
Ea
t uth
We
s So
Figure 3.1
Houses are orientated to face north, yet this will not always be possible in
relation to the street we live in. We would certainly want key areas within our
homes to enjoy sunlight throughout the year. These areas are either defined by
us or we leave it to the designers to choose.
2. Information is extracted from the drawings in terms of the setting out
requirements on site. (SO3 AC2).
When a building plan is drawn it must include all the information about the site
as well as the surrounding areas. This will assist the builder in planning the site.
These would include conditions above as well as below ground level. Some of the
important factors would include:
• The positions of any underground cables or storm­water pipes;
• The conditions of the soil
• Rivers or streams flowing through the property
• The positions of adjacent buildings
• Restrictions placed on the site by the local authority
• Large trees on site, or
• Any other obstacles that might hamper the setting out and construction
of the building.
2 Scales are interpreted and measurements converted in terms of actual
dimensions required. (SO3 AC3)
We have mentioned earlier that before a building can be constructed or built it
must first be presented in a form of a drawing. If we consider the size of a
building then it will be impossible to present the drawing on a drawing sheet.

23. This can however be done only if we represent the size of the drawing in
proportion to the actual size of the building. The huge football stadiums that
have recently been completed were all drawn to scale to fit on normal drawing
sheets. Figure 3.2 below show three views of a sports stadium. Each of the
100 m 100 m
stadiums was drawn to a different scale although the size remains the same.
50 m
50 m
100 m
50 m
Figure 3.2
Each drawing on a drawing sheet must have the scale of the drawing stated
below the draw. Drawings that are not drawn to scale will have the abbreviation
“NTS” written below the drawing. Let’s take a closer look at some popular
drawing scales. Architects and draughts­persons use a special scale ruler to draw
objects to different scales, yet the normal everyday school ruler can also used.
Figure 3.3 below show an ordinary school ruler being used to measure three
different scales.
In the ruler at the top, 1 millimetre on the drawing paper representing 1 actual
millimetre on site.
In the ruler in the middle, 1 millimetre on the drawing paper will represent 10
millimetres on site.
In the ruler at the bottom, 1 millimetre on the drawing paper will represent 100
millimetres on site. 75 mm
10 mm
0 5 10 20 30 40 50 60 70 80 90 100
Using an ordinary ruler to measure full size
750 mm
100 mm
0 5 10 20 30 40 50 60 70 80 90 100
Using the same ruler to measure to scale 1:10
7 500 mm
1 000 mm
0 5 10 20 30 40 50 60 70 80 90 100
Using the same ruler to measure to scale 1:100

24. Figure 3.3
When a drawing was drawn to scale 1:10 it would indicate that the drawing was
drawn 10 times smaller than the original size and the scale 1:1 000 indicates
that the drawing was drawn 1 000 times smaller.
For the more professional approach we can use the proper scale rulers, figure 3.4
below shows some examples of such rulers. A single scale ruler can as much as 8
different scales on one ruler.
1:200; 1:50 and 1:100
11,140 metres
3,8 m
0 5m 10m 15m 20m
SCALE 1:200
Each millimetre on the 1:200 scale equals 200 millimetres
3, 75 metres
1 250 mm
0 500 1m 2m 3m 4m 5m
SCALE 1:50
Each millimetre on the 1:50 scale equals 50 millimetres
7 500 mm
1 550 mm
0 1m 2 3 4 5 6 7 8 9 10
SCALE 1:100
Each millimetre on the 1:100 scale equals 100 millimetres
Figure 3.4
By reversing the scale, shown in figure 3.5 below, we will be able to draw small
objects to large scales:
• The scale 2:1 indicates that the object is drawn to twice its actual size.

25. • Some very small objects can be drawn to scale 5:1 which would indicate
that the object is drawn 5 times larger than the actual size.
11,140 metres
3,8 m
0 5 10mm 20mm 30mm 40mm 50
SCALE 2:1
Two millimetres on the 2:1 scale equals 1 millimetres
Figure 3.5
Important words and ideas
The golden rule to apply when reading scales are:
• If the number on the left is smaller than the number on the right, then we
are drawing large objects.
• If the number on the left is greater than the number on the right, then we
are drawing small objects.
Typical scales that are used on building plans are:
1:200 or 1:500 these are used to draw site plans;
1:100 mainly used to draw the plan layout and elevations;
1: 50 is used for sectional views;
1:10 or 1:5 are used for details
3 Dimensions are interpreted from the drawings in terms of site
requirements. (SO3 AC4)
A completed construction drawing for a building plan must consist of all notes
and dimensions before it is issued to the building contractor. The plan will also
state that all dimensions and levels be checked and verified before any building
work commences. This would imply that the builder is required to check the
levels and dimensions on site before the building is set out. It would be wise of a
site foreman to spend time with the plans and write down all important
dimensions, this would help him when he gets to the building site by which time
he would have a complete mental picture of the building. Checking the
construction drawngs would also eliminate any discrepancies which could be
cleared with the architect. Some of the important notes would include:

26. • The physical address of the site. This should be given at the bottom right­
hand corner of the drawing sheet, see figure 2 above, or at one of the
corners of the site plan which would indicate the measurement to the
nearest cross­road. The importance of this is that many buildings have
been built on the wrong site.
• The size and shape of the plot as stated on the site plan. The size of the
site boundaries are normally written at the corners of the site plan.
• The dimensions of the building lines in relation to the site boundaries.
There should be at least two dimensions showing the distance of the
building line from the front boundary and the distance from a side
boundary.
• The internal dimensions must be equal to the overall external dimensions
of the building. Should there be an error then the overall dimensions will
take preference over the sum of the internal dimensions. Any major
differences must be cleared with the architect before the commencement
of any work.
Take care to avoid common errors when copying dimensions from a plan.
Be careful with writing 2 960 instead of 2 690.
Activity 3:
1. What scales do you think were used to draw the football stadiums?
2. Measure the outside perimeter of your house then use a scale 1:100 to
draw the outside perimeter of your house on a sheet of paper.
3. Why is it important that buildings be orientated towards the north?
4. What important factors must be considered when checking the
construction drawings?
5. Obtain some typical building plans to see what scales were used to draw
the various drawings. Use a scale ruler to see if the dimensions are
correct.

27. UNIT 4 INTERPRET SPECIFICATIONS APPEARING ON
CONSTRUCTION DRAWINGS
By the end of this unit you should be able to:
1. Materials are identified in terms of ordering requirements (SO4 AC1)
2. Specifications and notes are explained in terms of work requirements.
(SO4 AC2)
1 Materials are identified in terms of ordering requirements (SO4 AC1)
The building and construction industry is probably the one industry which uses a
vast assortment of different types of materials to construct a building. The list of
building materials could be endless as new materials continue to enter the
market. Building materials are also evolving towards “old” or “used” materials
being recycled to make new materials. This whole new shift is aimed at stopping
us from using the earth’s natural resources. Ninety­nine percent of all building
materials are sourced from the depths of the earth.
During the design of the building the architect decides which materials will be
best suited for his design; he will also consider the environment where the
building is to be constructed. If the house is to be built close to the ocean then
rust­proof materials should be used. In areas where extreme wind conditions are
experienced then small span roof tiles will not be a good option.
Building materials must be ordered well in advance to ensure the continuity of
the project. Always check with the supplier about delivery time frames. Any
person with a sound knowledge of the building should be able to compile a list of
the required building materials from the building plans. The materials for the
plumbing and electrical work will not be included as it will be done by specialist
companies. For the sake of convenience we will divide the building into 4 phases
this will assist you when placing the orders for the materials:
1. The foundation up to the floor level;
2. The superstructure up to the roof level;
3. The roof structure, including the ceiling;
4. Finishing work
1. Materials required for the foundation up to the floor level.
• Sand and stone: This will be used when mixing the concrete. Sand and
stone is sold by metre cube (m³).

28. • Cement: This will be used when mixing the concrete. Cement is sold in 50
kg pockets.
• Bricks: These will be used to build the foundation walls of the house.
Bricks are sold in multiples of 1 000.
• Sand: The sand and cement will be mixed with water to make mortar for
the foundation brick work.
• Damp proof membrane: Sheet membrane is used as under floor damp
proofing for the concrete floor. The membrane is sold in 20 metre rolls in
widths of 1 m, 2 m, 3 m, 4 m and 6 m.
2. The superstructure up to the roof level
• Damp proof course: The DPC will be placed on top of the foundation walls,
when the walls of the house are ready to be built. Damp proof course is
sold in widths of 110 mm, 220 mm, 340 mm in rolls of 40 m
• Bricks: These will be used to build the walls of the house. Bricks are sold
in multiples of 1 000.
• Sand: The sand will be mixed with cement and water to make mortar for
the brick work, plaster for the walls and screed for the floors.
• Cement: Vital material for any construction. Cement is sold in 50 kg
pockets.
• Door frames: Timber frames for the external doors and pressed metal
frames for the internal door frames. When ordering metal frames, left or
right opening must be specified.
• Window frames: This will be specified on the building plan view. Consult
the relevant catalogue. Only the catalogue needs to be specified when
ordering windows (steel or timber).
• Brick reinforcement: Brick force will be used when building the top 4
courses of brick work, under the wall plate. (Refer to specifications below).
Brick reinforcement or brick force are bought in 20 m rolls of 3 m length
and in widths of 75 mm or 150 mm.
• Cavity tie wires: The tie wires are used to tie the two skins of brick work.
There are many different shapes and designs. Tie wires are calculated at
2,5 ties per metre square of brick work.
• Precast concrete lintels: The lintels will be placed over the door frames,
window frames and clear openings. Lintels are ordered in standard
lengths from 900 mm to 6.6 m in increments of 300 mm.
• Galvanised steel wire: The steel wires will be used to tie down the timber
roof structure. It will be built into the walls at 600 mm centres and at
least 600 mm deep.

29. • Fibre cement window sills: These will used to finish off the internal and
external window sills. The lengths of the sills correspond to the standard
steel window sizes (for example, 533 mm, 1 022 mm, 1 511 mm)
3. The roof structure including the roof ceiling
• Sawn softwood timber: The best option is to have a specialist timber roof
truss company manufacture the trusses. This is to ensure that all the
trusses are made to the exact specifications. The company is supplied with
a building plan. The trusses must be ordered well in advance. All timber is
ordered in metre lengths;
• Wall plates: These will be secured to the top of the wall to form a level
solid base for the roof trusses and consist of Sawn Softwood timber. The
wall plate timber must be 114 mm wide by 38 mm thick as is ordered in
standard lengths starting from 2,4 m or 3 m and in 300 mm increments up
to 6.6 metres. Be careful when ordering long lengths it has the potential
for waste due to warping and other defects.
• Fascia boards: The fascia boards will be nailed to the ends of the rafter to
finish off the roof structure. It is also a place where the gutters are fixed.
• Purlins or battens: This will be used to secure the roof covering.
• Roof covering: This could be metal sheeting, clay tiles or fibre cement
sheeting;
• Brandering: These are battens that will be used to secure the ceiling
boards;
• Gypsum rhino boards: Used for ceiling boards.
• Cove cornice: to cover the gap between the walls and the ceiling.
• Gutters and down pipes: To lead the rainwater away from the building.
4 The finishing work
• External and internal doors;
• Timber skirting for the floors;
• Glass panes for the windows;
• Bathroom fitments; bath, wash basin, water closet;
• Kitchen sink;
• Ironmongery and finishing; door locks, toilet roll holders, towel rails,
curtain rails;
• Cupboards and wardrobes
• Paint for the walls and ceiling

30. • Varnish for the doors and skirtings;
• Carpets and tiles for the floors;
Materials not shown on the drawings
Part of the finished product, but not usually found in descriptions or shown on
drawings, are the many types of fasteners used in assembling a building. These
would include nails, screws, bolts, roofing screws, plugs, wire, hoop iron
Galvanised steel straps), brackets and connector plates, adhesives, tile grout,
cement slurry or patent products used to provide key or grip between concrete
and plaster.
Then there are also the consumables, these are materials that will be used up
and then replaced. Consumables and are not shown on any contract documents.
The contractor still must estimate their quantities for inclusion in the estimate
or budget, and because they have to be purchased as well. Some examples of
consumables are:
• Sanding paper, thinners, brushes that are used up in painting operations;
• Drill bits, angle grinder cutting discs and saw blades used up on the
project;
• Plastic spacers for wall and floor tiling;
• Cleaning materials that are used for cleaning mortar splashes off face­
brick work and tiling;
• Cloth and detergents used for general cleaning of the works.
The quantity surveyor, in calculating the cost of the building, uses the drawings
and specifications to calculate the exact amount of materials that will be
required to build the house.
The building contractor also uses the drawings and specifications to purchase the
materials.
The difference between the quantity surveyor and the contractor, where the
materials are concerned, is that the quantity surveyor will use the exact amount
whereas the contractor must allow for waste.
An example of this is:
Suppose a room needs to be fitted with a skirting board. The room consists of
four walls each measuring 3 metres in length. The quantity surveyor’s bill of
quantities will reflect that 12 metres of skirting is required. The contractor on
the other hand might have to purchase 13 metres of skirting to allow for
cutting the joints and fitting the skirting.

31. 2 Specifications and notes are explained in terms of work
requirements. (SO4 AC2)
Specifications and notes are used to compliment the drawings with information
that cannot be shown on a drawing. Notes and specifications can also be
combined. Let’s say the plan layout of a room states that the floor of a room must
be carpeted; this will regarded as a note. The specific type, colour, make and
fitting instructions of the carpet will then be specified in the specifications. Other
examples of notes which can be found on a drawing will include:
• All timber attached to brickwork must be coated with wood primer;
• The wall cavity below the floor level must be filled with weak concrete;
• The size of the shower tray must be minimum 900 mm x 900mm;
• The shower cubicle must be fitted with a shower curtain;
• All the walls must be painted with three coats of paint;
• The top four courses of the cavity wall below the wall plate must be built
solid;
• All dimensions and levels must be checked and verified before the
commencement of any work;
Examples of specifications will state the type and grade of materials that must
be used, example:
If the drawing indicates that a house must be built with bricks, then the
specifications will state the type and sometimes the colour of the bricks. The
specification will read;
• All the walls must be built with NFP (non­facing plastered) clay bricks.
As a specification for the roof timber, it will state that;
• All roof trusses shall be constructed of Sawn Softwood timber with a
moisture content of not less than 17%
Activity
Look around your house and compile a list of all the materials that was used to
construct the house; don’t forget to look inside the ceiling.