Construction
Science
Mr. M Mathenjwa
Cost construction
11/03/2025
• COSTING CONSTRUCTION WORK MATERIAL & LABOUR
LECTURE CONTENT
•Did you know…?
•Costing construction work – materials &
labour:
1. Introduction
2. Foundations
3. Cavity walls
4. Flooring
5. Painting
WHY IS IT IMPORTANT
TO ACCURATELY COST
CONSTRUCTION
WORK?
1. INTRODUCTION
• One of the important branches of building technology is to prepare the
estimates of the cost involved in constructing a building.
• The overall cost of a project determines its viability and enables the client to
arrange capital for financing the construction.
• The main components of the cost of constructing a building are the cost of
materials, labour, plant and contractor’s profit.
• This chapter gives some examples on how to prepare approximate estimates.
The costs of materials and labour are never constant and they also differ
from one region to another. For latest information on the cost of materials,
labour and plant reference should be made to publications which update this
information at regular intervals.
PAINTING
• Painting is necessary to give doors, windows, walls etc. a finish that
enhances their appearance and provides protection from dust, dirt and
other harmful substances. In this section only the external surfaces of
walls are considered. Some of the main factors that affect the amount
of paint required are the type of surface, the number of coats and the
type of paint.
EXAMPLE 4 - The front wall of a house,
shown in the below figure, is finished with
roughcast rendering and needs two coats
of masonry paint. The spreading rate of
paint is 3m² per litre. Find the cost of paint
and labour if one 5 litre can of masonry
paint costs £15.89, and the labour cost is
£4.30 per m².
4. FLOORING
• Softwood boards and chipboard sheets are used as floor covering
materials in dwelling houses. The thickness of these materials depends
on the spacing between the floor joists. For a spacing of 400 mm between
the joists, 18 mm thick floorboards and chipboard sheets are satisfactory.
The coverage provided by tongued and grooved floor boards/chipboard
is slightly less than their actual surface area as the tongue of one board
fits into the groove of the next one. A floorboard measuring 2400 x 121 x
18 mm provides coverage of 0.272m².
• The figures on the right, shows the joists and floorboards of an upper
floor.
EXAMPLE 3 - Find the cost of providing and
fixing:
(a) softwood floorboards in a room measuring
4.5m x 3.9m
(b) chipboard flooring in a room measuring
5.0m x 4.2m
Floorboards measuring 3000 x 121 x 18 mm
thick cost £16.99 for a pack of five. One pack
covers an area of 1.71m². Cost of labour is
£9.00/m².
One sheet of chipboard measuring 2400 x 600
x 18 mm thick costs £5.30. One sheet covers an
area of 1.44m². Labour cost is £4.50 /m².
Allow wastage @ 10%.
3. CAVITY WALLS
• The cavity walls in dwelling houses consist of a 102.5 mm thick
outer leaf of bricks and a 100 mm thick inner leaf of lightweight
concrete blocks. The space between the two leaves, called the
cavity, is 50 to 75 mm wide and provided with 50 mm thick
Rockwool or other insulation material suitable for the purpose.
• The below figure shows a brick and a block as they are laid in the
construction of walls. The dimensions shown are without the
mortar joints. With 10 mm thick mortar joints their dimensions are:
Bricks: 225 x 102.5 x 75mm/Concrete blocks: 450 x 100 x 225mm
• The quantity of mortar required for 1m² of brickwork is 0.026m³
and for 1m² of blockwork is 0.012m³.
EXAMPLE 2: Calculate the number of bricks and 100 mm thick aerated concrete blocks, and
the quantities of cement and sand, to construct a 4.0m x 2.8 m high cavity wall with a 2.0m x
1.2 m high window. Allow for 5% extra bricks and blocks and 10% extra mortar. Labour rates
are: £15.00/m² for brickwork and £11.50/m² for blockwork.
SOLUTION:
2. FOUNDATIONS
• Concrete is by far the most commonly used material
in the construction of foundations of buildings. For
plain concrete 1:3:6 concrete mix is usually used, but
for reinforced concrete 1:2:4 or a stronger mix is
used.
• In this section we will consider how to work out the
mass of the cement and the aggregates. This gives a
better quality of concrete as we can take into account
the moisture content of the aggregates if they are not
dry.
• Consider a 1:3:6 concrete mix. The density of concrete
is approximately 2400 kg/m3 or in other words, 1m3
of concrete has a mass of 2400 kg . To prepare 1m3 of
concrete the quantities of cement and the aggregates
are:
• The amount of water depends on where the concrete
is to be used. For Strip foundations the amount of
water could be about 50% of the amount Of cement,
giving a water cement ratio of 0.5.
• EXAMPLE 1 (NB!!!) - Calculate the cost of materials and
labour required to construct the 1:3:6 concrete strip
foundation shown in the figure, given that:
Solution:
solution
Volumes, the quantities of material to prepare 1m3 of
concrete are given. For preparing 3,552m³ of concrete,
the quantities of materials and their costs are:
EnD
• Scope?
• Unit converions
• Indices
• Basic algebra and transpositions