Transcript the building team

BUILDING TECHNOLOGY
REVISION HANDBOOK
Module D12
Building Teams and Building Trade
THE BUILDING TEAM
THE BUILDING TEAM
Building is essentially a team process in which each
member has an important role to play.
QUANTITY SURVEYOR
Below are some key points and a typical organization
structure of a team for a large construction project.
KEY POINTS
1. The client decides that a building is needed and
employs the building and design team
2. The architect, who is a key member of the design
team, designs the building for the client. Other
members of the design team are: the structural
engineer; the quantity surveyor; the clerk of work
NOMINATED
SUB-CONTRACTOR
3. The building team works for the client, but follows the
design teams instruction
OPERATIVES
4. The main contractor constructs the building with
assistance from subcontractors
CONTRACTS
5. Skilled technicians assist all parts of the building
SURVEYOR
MANAGER
process
ASST. CONTRACT
6. Building merchants supply the building material
MANAGER
7. Building inspectors are responsible for building
DOMESTIC
regulations
SUB-CONTRACTOR
8. Planners control the overall design and siting of
building projects
OPERATIVES
BUILDING OWNER/CLIENT
ARCHITECT
ENGINEER
PLANNING AUTHORITY
LAWYER
BANKER
CONTRACTOR
ESTIMATED
BUYER
CLERK OF WORKS
ADMINISTRATOR
COSTING
ACCOUNTS
OFFICE STAFF
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Functions of the members of the
Building Team
Client – the person who commissions the work and directly or
indirectly employs everybody on the project.
Architect – engaged by the client as his/her agent to design, advise
and ensure that the project is keeping within cost and complies
with the design.
Contractor – employed by the client on the architect’s advice to
carry out the constructional works. He takes his instructions from
the architect.
Engineer – a specialist such as a structural engineer employed to
work with the architect on particular aspects of the design.
Quantity surveyor – engaged to prepare bills of quantities, check
tenders, prepare interim valuations and advise the architect on the
cost of variations
Building Trades
• The building industry has a number of trades
associated with it. These include:
– Carpenter
– Mason/tiler
– Painter
– Electrician
– Plumber
Responsibility of members of the
Building Trade
• Carpenter – erects structural framework and
constructs roofs
• Electrician – carries out wiring works and installation
of fixtures
• Plumber – lay pipes, install taps, toilet bowls, etc.
• Painter – responsible for finishing the building by
applying paint, wall paper
• Mason/tiler – works with concrete and mortar, lay
concrete blocks, plaster walls etc.
Module D2
Preliminary Site Work
FACTORS AFFECTING CHOICE OF A BUILDING SITE
KEY POINTS
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ZONING-is the legal identification of lands for specific use. The general categories of zoning
are:-Residential, Commercial Industrial and Agricultural.
OTHER FACTORS
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Land use - be sure that it can be used for the intended purpose.
Ownership - ownership, certified by a deed (legal document) must be established before any
final decision is taken regarding purchase of any lands.
Boundaries - must be established and supported by a survey drawing before the actual size
of property can be ascertained.
Shape – when purchasing land, the shape of the lot (plot) should reflect the proposed shape of
the structure within the framework of the legal restriction.
Size – minimum sizes of building lots are usually specified in order to ensure that: - legal
requirements of set-back and off-set distances are satisfied.
Topography – is the shape of the surface of the land. This shape is sometimes referred to as
“contour” and be classified as follows: Flat/Undulating/Gently slope/Steeply sloped
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History – is the study of past events associated with the use of the site. Historical
issues that should be of concern to the purchaser are:
– Water – whether natural water course, springs or flooding are associated
with the site.
– Dump – whether the site was ever used as a dump.
– Original topography – whether the land was filled.
• Access – all lands not immediately adjoining a street or public
• pathway requires some means of access. This access influences movement to
and off site during construction stage as well as normal occupancy.
• Unit cost – is the price per square foot or meter of the land. This unit
cost is normally associated with:
– Level of development
– Available amenities
– Available services
– Location
– Zone
– Demand
– Topography.
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STRIPPING AND CLEARING OF A BUILDING SITE
STRIPPING is the removal of topsoil from the construction area. Stripping should include pathways and aprons.
REASONS FOR STRIPPING
• Stripping helps to provide a sound and level platform as well as to remove vegetable matter. Soils containing a
high level of vegetable matter tend to:
• Support plant life
• Be very unstable
• Affect some building materials
• A site is usually stripped to a depth of about 150mm/6’’ using a bulldozer.
CLEARING
Clearing is not necessarily part of stripping but for undeveloped sites, clearing is essential.
REASONS FOR CLEARING
• The removal of trees, which sometimes may obstruct the building process. OR
• Traffic flow on site.
• The removal of obstacles like derelict buildings, vehicles, large boulders
or debris that may hinder the building process
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Hoarding
One of the first jobs is to lay out the site boundaries, this is known as hoarding. This is done for
the following reasons:
Reasons for hoarding:
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- Public protection
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- Material/equipment protection
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- Security
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- Reduces vandalism
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- Prevents interruption
Explanatory notes for reasons given:
• Public protection – to reduce the risk of accidents by keeping activities on the site away from
outside persons
• Material/equipment protection – to reduce theft of materials
• Security – to ensure workers and equipment are safe on the site.
• Reduces vandalism – prevents persons from interfering or destroying items on the site.
• Prevents interruption – persons or animals from the outside would not be able to distract
workers on the site
Lay out simple building/structure
Peg the outside corners:
Determine the location of the building in relation to other buildings and boundaries (as usually
shown on the site-plan or other relevant plan), and place pegs in the ground marking the corners
of the building
Steps in laying out a Square Building
Check to see if the pegs are square and form an exact rectangle. This can be done by making sure
that:
1). Line AA-CC and line BB-DD are parallel.
Line AA-BB and line CC-DD are parallel.(as shown in the drawing below)
2). The distance between peg AA and peg BB
is the same as the distance between peg CC and peg DD.
3). The distance between peg AA and peg CC is the same as the
distance between peg BB and peg DD.
4). The distance between peg AA and peg DD (the diagonals) is
the same as the distance between peg BB and peg CC.
Simple Building Squaring: The 3–4-5 Method
Here is a simple way of squaring a structure you are building outside.
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Nail three pieces of timber together which you cut to these lengths to
make a frame
750mm
1000mm
1250mm
A frame with a right corner is called a square.
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Place the right of the square against the lines between the corner . If the
corner are not at right angles then move the corner pegs until they make
right angles
Corner post
3-4-5 triangle
Checking squareness after setting out
Main setting out lines
Profile boards
The other method of checking
squareness of a building is to
check the diagonal. If the
diagonals are of equal lengths
then the building is square
Diagonal
checks
TEMPORARY SERVICES ON A BUILDING SITE
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DEFINITION
Temporary services relate to the provision of utilities for the purpose of facilitating construction activities as
well as providing convenience for workers. These supplies normally include: gas, water, compressed air,
electricity and telephone.
CONVENIENCES
These include convenience for personnel and work processes.
PERSONNEL: Temporary services assist in the provision of drinking water, adequate lighting and toilet
facilities.
WORK PROCESSES: Utility supplies to the site can be used to drive (power) plant and equipment or provide
ingredients for preparing certain materials.
Examples of supplies used for driving plant and equipment are:
Air – pneumatic tools and equipment
Oil and gas – turbine and hydraulic tools and equipment.
Electricity – electric tools and equipment
Heat, water and air are used in the following processes:
Heat – asphaltic processes
Water – mixing concrete
Air – spray painting, excavating compacting
COMMUNICATION
Communication includes physical and verbal contact between the various agencies and processes during the
life of the project. Factors to be considered are temporary roads for access to the site and storage areas, as
well as possible telephone or two-way radio contacts.
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Module D3:
Building Material
MANUFACTURING PROCESS OF PORTLAND CEMENT
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WHAT IS CEMENT AND HOW IT IS MADE
Cement is a fine, soft, powdery-type substance. It
is made from a mixture of elements that are found
in natural materials such as limestone, clay, sand
and/or shale. When cement is mixed with water, it
can bind sand and gravel into a hard, solid mass
call concrete.
Step 1
Limestone is taken from a quarry. It is the major
ingredient needed for making cement. Smaller
quantities of sand and clay are also needed.
Limestone, sand and clay contain the four
essential elements required to make cement. The
four essential elements are calcium, silicon,
aluminum and iron.
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Step 2
Boulder-size limestone rocks are
transported from the quarry to the cement
plant and fed into a crusher which crushes
the boulders into marble-size pieces.
Step 2
Step 3
The limestone pieces then go through a
blender where they are added to the other
raw materials in the right proportion.
Step 3
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Step 4
Step 4
The raw materials are ground to a
powder. This is sometimes done with
rollers that crush the materials against a
rotating platform.
Step 5
The rawmix or slurry is fed into a sloping
kiln which is fired from the lower end by oil
or pulverised coal to a temperature of
2000 F or 1500 C by the time it reaches the
lower end the water has evaporated and
fusing of materials takes place forming
clinker.
Step 5
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MANUFACTURING PROCESS OF PORTLAND CEMENT
Step 6
The clinker is cooled and ground into a
fine gray powder. A small amount of
gypsum is also added during the final
grinding. It is now the finished product –
Portland cement.
The cement is then stored in silos (large
holding tanks) where it awaits distribution.
The cement is usually shipped in bulk in
purpose-made trucks, by rail or even by
barge or ship. Some is bagged for those
who want small quantities.
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The five easy steps in the production of Portland Cement
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Crush and grind raw material
Mix the material in proportions
Heat and prepare mixture in rotary kiln
Grind the heated product known as clinker
Mixing and grinding of clinker with gypsum
TYPES OF PORTLAND CEMENT
Five common types of cement
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Type I or Normal
This type is ordinary Portland cement. It has normal qualities, a reasonable setting time.
USES: For general concrete work, when conditions are normal- including masonry work rendering, filling of pockets
ordinary strip foundation in concrete.
Type II – Moderate (sulphate resistance)
This type of cement gives off less heat than type I and has moderate resistance to sulphate.
USES: Suitable for uses in foundations where there are low levels of sulphate but offers good resistance to soil in
which there are high levels of sulphate.
Type III – Low Heat
This type is ideal for use in mass concrete work, such as large foundations or dams retaining walls. It develops
strength slowly and generates less heat thus reducing cracking.
Type IV- High Early- Strength or Rapid Hardening
This cement is used when the weather is bad (rainy season) or when formwork has to be removed early. It develops
strength earlier than types I and II.
Type V- Aluminium
This type contains aluminium ore. It is darker in the colour than normal Portland cement. It hardens very rapidly and
has great strength.
Concrete and Mortar
CONCRETE
Contrary to popular belief, concrete and cement are not the same thing; cement is actually just a component of
concrete. Concrete is made up of three basic components: water, aggregate (rock, sand, or gravel)
and Portland cement. Cement, usually in powder form, acts as a binding agent when mixed with water and
aggregates. This combination, or concrete mix, will be poured and harden into the durable material with which
we are all familiar. There are three basic ingredients in the concrete mix: Portland Cement Water and
Aggregates (rock and sand)
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Concrete is a composite material composed of a mixture of cement, sand, gravel and water in the correct
proportion to form a paste that can be moulded into any shape. Concrete is used
for columns, beams, foundation etc.
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Mortar is a mixture of cement, sand and water mixed in correct proportion. Mortar is used for making beds, for
laying bricks and for rendering masonry walls
When prepared concrete and mortar has to be mixed to a specific proportion depending on the job it required to do.
the standard mix for small jobs are usually done in the ratio of 1:3:6.
This represents a mix of 1volume of cement, to 3 volumes of sand, to 6 volumes of course aggregate.
Water- Water is needed to chemically react with the cement (hydration) and too provide workability with the
concrete. The amount of water in the mix in pounds compared with the amount of cement is called the water/cement
ratio. The lower the w/c ratio, the stronger the concrete. (higher strength, less permeability)
BATCHING OF CONCRETE
Types of batching
Batching by volume
Volume batching is generally used but it is a less
accurate method of mixing concrete. The measuring
box/bucket/wheel barrow is used to determine the
amount of cement and aggregates. A change in the
moisture content will impact upon the volume of
materials and affect the qualities of the concrete
BATCHING PLANT
MIXING CONCRETE BY WEIGHT AND VOLUME
Batching by weight
In this method the ingredients are measured by weight.
This is a more reliable system of batching that volume
batching. Variation in volumes owing to compacting is
eliminated when using this method.
The result of batching
• Strength – in order to obtain maximum strength the
aggregates must produce little or no voids in the concrete
thus increasing its strength.
• Economy- cost is a major factor in concrete work. Cost is
influenced by careless use of ingredients. The most costly
ingredient is the cement. A poor mix often increases the
cost of the job or reduces the strength of the concrete.
• Workability- this is the ability of the wet concrete to be
placed and work with ease. The correct proportioning of
the cement and the aggregates and water cement ratio
enhances this property.
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THE WORKABILITY OF CONCRETE
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Pouring a concrete floor for a commercial
building.
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Adjusting the reinforcement bars during a
concrete pour
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A concrete slab ponded while curing.
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AGGREGATES
Aggregates is the general terms for the sand and rocks used in construction. Fine aggregates are sand and
coarse
aggregates are gravel or crushed stone. Aggregates are size graded and sold by set size categories,
measured as
inches or millimetres.
Requirements of Aggregates
• All aggregates should be:
• Clean
• Free from all sediment
• Strong not easily crushed
• Well graded
• Well shaped
Types of Aggregates
• Coarse Aggregate gravel consists of small pieces of stone which are somewhat rounded in shape. It
makes good coarse aggregate because it is hard and closed textured. When using gravel as a coarse
aggregate the pebbles should be graded in size – (Source – Gravel Bank, River Beds).
• Crushed Stone trap rock is the hardest and most durable stone that can be crushed and used for
making concrete. This stone is dark, heavy, close-grained, and of igneous origin. Granite makes good
crushed stone and is less expensive than trap rock.
• Fine Aggregates for concrete are sand and crushed stone or gravel screening. The most important of
thee (by far) is sand. Sand is a finely divided material of rock or mineral origin which will pass through a
standard 5 mm sieve. Sand is not subject to disintegration, decay or expansion.
• All–in: The term all-in is used for aggregates composed of both fine and coarse aggregates. A wide
variety of material, for example brick, furnace slag, lightweight substances such as foam slag, expanded
clay and vermiculite are available as aggregates for making concrete.
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Slump Test
• The slump test is carried
out to measure the
distance that concrete
compacted into a cone
will slump down when he
cone is lifted from it. The
slump will be the same
for batches if the water
content is consistent.
Placing Concrete
The following are precautions to be taken when placing concrete:
1. Mixed concrete should be placed in its final position within half to an hour of
mixing. This is because the initial setting of ordinary Portland cement takes
place within this period of time. After this time, the concrete has lost some
strength which can never be regained.
2. Concreting in hot dry weather poses particular problems with regards to placing.
Moisture evaporates too fast rapid and this can result in a weak finished product.
3. When concrete is being laid in foundation trenches, in addition to the fast
evaporation of moisture from the concrete, the dry trench absorbs moisture
from the concrete. To limit this absorption, the trench should be watered down
before the concrete is placed into it
4. Concrete shouldn’t be dropped from a great height, as this tends to segregate
the aggregate. A height of 1meter is usually specified as the maximum from
which wet concrete should be allowed to drop freely
5. Soon after placing in the right position concrete should be compacted or
consolidated. The purpose of compacting is to make the concrete as dense as
possible by eliminating voids within it.
6. All formwork must be plumbed, leveled and adequately supported.
CURING AND PROTECTING CONCRETE
Curing is the process of limiting early loss of water from concrete thus ensuring the
continuation of chemical action.
Losing too much water too early in the life of a concrete component causes high creep
and shrinkage, and may even cause a significant loss of strength.
Most importantly, poor curing is detrimental to the durability of the concrete, particularly
the outer concrete which is required to provide protection to the embedded
reinforcement. In general, the longer the period of curing, the better will be the quality
of the concrete. This applies not only to its compressive strength, but also to its
durability, its resistance to wear, weathering and chemical attack, and to its freedom
from shrinkage cracking. Concrete therefore needs to be kept moist, both by the
prevention of loss of moisture due to evaporation, and by the provision of extra water
from outside the concrete.
There are two general forms of curing:
• Keeping all concrete surfaces wet to prevent moisture loss (spraying with water)
• Creating a barrier to prevent moisture loss (sandbags, ponding)
D3.2: Plastics and Water proofing Material
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THE USE OF PLASTICS IN THE CONSTRUCTION
INDUSTRIES
Properties of Plastics
Lightweight
Durable
Easily jointed or molded
Glazable
Elastic
Uses of Plastic in Construction
Electrical conduits
Water seals, (DPC) Damp Proof Coarse, (DPM)
Damp Proof Membranes
• Floor/roof tiles
• Decorative skirtings/mouldings
• Water pipes
• Drain pipes
Conclusion:
With the increase of modern technology
plastics have not only make a big impact in
the construction industry but in other areas
such as medicine (prosthetic, plastic surgery),
transportation (vehicle manufacturing) and
communication (fiber optic cables and cell
phones).
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D3.3: Timber and Timber Products
GROWTH AND STRUCTURE
OF TIMBER
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SECTION OF A TREE TRUNK
The Parts of a Tree Trunk
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Bark
– Every species of tree has its own particular kind of
bark. This is a means of identification. The bark is
the protective coating of the tree.
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Cambium Layer
– This is the growing part of the tree trunk. Here
new cells are constantly developing, some making
bark and others making wood.
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Sapwood
– This is found next to the cambium layer, and
contains only a few living cells and functions mainly
in the storage of plant food and the conveyance of
sap. The sapwood varies in thickness from 13mm
to as much as 150mm radial thickness in some
species.
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Heart Wood
– It consists of inactive cells that have slightly
changed both chemically and physically from cells
found in sapwood. These cells cease to transport
sap. The cells of heartwood may contain minerals,
which contribute to its darker colour, great beauty
and resistance to decay.
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HARDWOOD AND SOFTWOOD
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There are two main groups of timber producing
trees used commercially; softwoods and
hardwoods. These terms immediately create
contention because they do not accurately
describe the timber correctly.
Softwoods. Softwoods are coniferous trees and
the timber is not necessarily 'soft'. They are
'evergreen'. (The larch is an exception) Their
general characteristics are:
Straight, round but slender, tapering trunk. The
crown is narrow and rises to a point.
It has needle like or scale-like shaped leaves and
it's fruit, i.e. it's seeds are carried in cones. The
bark is course and thick and softwoods are
evergreen and as such do not shed their leaves in
autumn.
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Hardwoods. Hardwood trees are broadleaf and
generally deciduous. Their timber is not
necessarily hard. For instance, balsa (the timber
used for making model planes) is a hardwood.
The general characteristics are: Stout base that
scarcely tapers but divides into branches to form
a wide, round crown. The leaves are broad and
may have single or multi lobes. The bark may be
smooth or course and varies in thickness and
colours.
Its fruit may be: nuts, winged fruits, pods,
berries, or fleshy fruits.
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Hardwood
Softwood
Density:
higher density thereby harder
Lower density thereby most
varieties are softer than
hardwood.
Found in
regions:
Trees supplying hardwood are found throughout the world
from the Boreal and Taiga forests of the North to the
tropics and down into the far South, excluding
Antarctica.
Found in the northern
hemisphere.
Definition:
Comes from deciduous trees that drop their leaves every
year.
Trees that are conifer and have
needles, and normally do
not lose needles.
Properties:
Broad leaves; enclosed nuts; higher density.
Less dense; less durable; high
calorific values.
Type:
Mostly deciduous.
Evergreen
Cost
Expensive.
Less expensive.
Examples of
trees:
Aspen, Poplar, Birch, Elm, Maple, etc.
Pine, spruce, cedar, fir, larch,
Douglas-fir, etc.
Applications:
Used for furniture but less frequently than softwood.
Widely used as wood ware for
building and furniture.
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CONVERSION OF TIMBER
Methods of Conversion
Plain Sawing or Through and Through Sawing – this
method yields the maximum amount of usable wood
from the log, but logs cut in this way will also include
growth defects which may result in poorer quality timber.
Advantages
More lumber is produced
It dries more rapidly
It is cheaper
It has a lower unit cost
Quarter Sawn – this method is used when first quality
timber is required, however a fair amount of waste is
produced from this method. This is one of the reasons
for the high cost of good quality timber.
Advantages
Less tendency to warp or twist
Less tendency to cut or twist
Less shrinkage
More durability – strength
More attractive grain pattern
More rapid kiln drying
Tangential Sawing – this method is used to get boards
with the maximum amount of grain configuration suitable
for decorative work. However due to the cost of
producing this kind of timber the logs are cut into veneers
instead.
P.S. Any waste timber that occurs during conversion is
recycled in the manufacture of certain building boards
such as plywood.
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SEASONING• OFKILNTIMBER
SEASONING
Seasoning is the controlled process of reducing
the moisture content (MC) of the timber so that it
is suitable for the environment and intended use.
We need to reduce the MC of timber for the
following reasons:
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Seasoned timber although lighter will be stronger
and more reliable.
The sap in timber is a food for fungi and wood
parasites. Remove the sap and the wood will be
less attractive to these dangers.
For construction grade timber the timber must
be below 20% MC to reduce the chances of Dry
Rot and other fungi infestations.
Dry well seasoned timber is stronger.
Dry well seasoned timber is easier to work with
and consequently safer especially machine
working.
Timber with higher moisture content is difficult
to finish i.e. paint, varnish, etc.
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AIR SEASONING
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TYPES OF SEASONING
There are two main ways of seasoning timber,
Natural (Air) and Artificial (Kiln) drying. Both
methods require the timber be stacked and
separated to allow the full circulation flow of air,
etc. around the stack.
Kiln Seasoning.
There are two main methods used in artificial
seasoning, compartmental, and progressive. Both
methods rely on the controlled environment to dry
out the timber and require the following factors:
Air Seasoning.
Air seasoning is the method used with the timber
stacked in the open air. It requires the following:
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Stacked stable and safely with horizontal spacing
of at least 25 mm.
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Vertical spacing achieved by using timber battens
(piling sticks) of the same or neutral
species. Today some timber yards are using
plastics. The piling sticks should be vertically
aligned and spaced close enough to prevent
bowing say 600 to 1200 mm max centres.
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Ends of boards sealed by using a suitable sealer
or cover to prevent too rapid drying out via the
end grain.
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The stack raised well clear of the ground,
vegetation, etc to provide good air circulation
and free from rising damp, frost, etc.
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Over head cover from effects of direct sunlight
and driving weather.
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Forced air circulation by using large fans, blowers,
etc.
Heat of some form provided by piped steam.
Humidity control provided by steam jets.
The amount and duration of air, heat and humidity
again depends on species, size, quantity, etc.
Schedules are published for the various species to
enable operators to select an appropriate drying
environment. In the UK they are usually provided
by the Kiln Manufacturers and also published in
the Handbook of Hardwoods and Handbook of
Softwoods (BRE).
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Calculation of moisture content
As mentioned before , for stability, timber should have a 20 percent moisture content, which is
close to the moisture in air.
The formula for calculating the moisture content is:
Weight of sample with moisture
dry weight
Example
A piece of timber weighs 132.5g
Its dry weight is 108.7g
The moisture content weighs 23.8g
The percent of the moisture content is
(23.8/108.7) x 100 = 21.9percent
x100
Defects in Timber
The defects that usually occur in the timber may be
classified into two categories as follows:
 Defects that
develop  Defects that develop after
during growth of the tree.
felling the tree.
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Shakes
 Twisted timber
 Upsets or rupture
 Knots
 Wind cracks
 Burls
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Bow
 Cup
 Twist
 Radial shakes
 Wane
 Diagonal grains
Defects in Timber
Defects that develop during growth of tree have been briefly discussed as follows:
1.1 Shakes. This is most serious type of defect in timber. These are sort of cracks which partly or
completely separate the fibers of wood. A shake is nothing, but separation of the timber
along the grains. Shakes may be of several types.
1.1.1
Star shakes
These are radial cracks or splits that extend from bark towards the
sap wood. They usually remain confined up to the plane of sap
wood only. The cracks are widest at the circumference and go on
narrowing as they proceed towards the Centre of the tree.
Defects in Timber
Star shakes
Reasons of star shake
Star shakes usually
develop due to fierce heat
and frost
When logs having this
defect are sawn they
usually separate out into a
number of pieces and
hence become useless.
Defects in Timber
1.1.2 Heart shakes.
These splits or cracks occur in the central part of the trees.
There are widest at the centre and go on narrowing as they
proceed towards outside. This defect usually occurs in overmatured trees. This defect is usually caused due to shrinkage of
the heart wood. Heart shakes divide the tree cross-section into
several parts. Straight running heart shake is not as serious as
twisted heart shake.
1.1.3Cup shakes.
This defect develops curved slit between successive annual
rings. The split does not run for the full circumference of the
annual rings. This defect usually develops due to:
1. unequal growth.
2. Another possible reason for their development may be
contraction of timber under atmospheric changes together
with the twisting action of strong winds.
Defects in Timber
1.4 Knots.
Knots are generally developed at the bases of branches cut
off from the tree. This phenomenon ultimately results in
the formation of dark, hard rings, known as knots. As knots
break the continuity of the wooden fibers, they form a
source of weakness. The amount of weakness caused by
the knot depends upon the position, size, and degree of
grain distortion around it. Knot is the most commonly
encountered defect of wood.
It is impossible to procure timber free of knots. Knots may be dead, live loose,
or tight. Tight knots are not objectionable unless they are too large. Their
presence on tension members is objectionable. It is very difficult to plane
the timber at knots
Defects in Timber
2. Defects that develop after felling the tree.
Conversion of timber is done almost immediately after felling The tree. The defects that may
develop after felling the tree and also during conversion and seasoning are the following:
2.1 Bow: when planks of converted of timber shrink and bend in curved form , in the direction of length.
2.2 Cup:
this defect is indicated when wooden planks bend in curved from in
transverse direction.
2.3 Twist
A plank which has distorted spirally along its length
Preserving Timber
• Timber should have two types of preservation applied
1.
Treatments of resist attack by rot fungus and wood-eating insects.
2.
Treatment such as paint, polish or vanish to protect it from moisture and pollution
Timber to be treated with preservative should be cut, shaped and prepared in advance of the
building work. Ant cutting afterwards exposes untreated timber, which must have liquid
preservative applied by hand.
Two methods can be used to treat timber:
1. pressure impregnation
2. Steeping or immersion
Pressure impregnation is a method whereby you put the timber in a kiln or other container and
create a vacuum inside by pumping out the air. You use pressure to force the preservative deeply
into the timber
Steeping or immersion is a method where you put the timber in a tank filled with preservative. The
timber absorbs so much liquid that it is full of the chemical preservative when it dries out again
Advantages of Treated Timber
• It provides long life under hazardous conditions.
• It is cost efficient.
• It is versatile – can be used outdoors, indoors, above ground, underground, and in direct contact
with fresh or salt water.
• A variety of finishes provide additional attractiveness.
• It provides flexibility for design and can economically overcome difficult site situations.
40
MANUFACTURED BOARDS
•
Manufactured or man made boards - are made from wood products and have new/different
properties to the wood they were made from. Board sizes are 8ft x 4 ft (2440 x 1220 mm).
Properties of Manufactured board:
1. Larder size the nun manufactured board
2. Uniform texture
3. Smooth surface
4. Standard dimension 8ft x 4ft (2440 x 1220mm)
MDF (medium density fibreboard) made by a process which glues wood fibres together using heat and
pressure. The boards are smooth and strong. They are resistant to warping. They have a layered structure
which makes fixing to the edges difficult. MDF is a board used industrially for the production of furniture
(especially shelves and cupboards). Special fixings have been designed to enable MDF to be joined
effectively. Dowel joints can be used. The router can be used to cut rebates and housing joints, which work
well on MDF. Dust is a problem when working with MDF, dust extraction systems should be used when
machining it. Face masks can also be used to reduce the problem
Plywood is made from layers of thin wood glued together at 90 degrees to each other, this makes plywood
very strong as it cannot split along the grain like solid timber. If waterproof glue is used the plywood can be
used in damp or even wet conditions. Marine ply can withstand sea water. Aero ply is made from three thin
layers of birch and is only one mm thick when bonded together, this ply was designed to be used on
aeroplane wings as it can be curved so effectively
41
MANUFACTURED BOARDS
•
Hardboard manufacture consists of breaking down wood into its basic fibers then putting
the wood back together with the fibers rearranged to form hard panels which have their
own set of separate and distinct characteristics. In a most real sense “hardboard” is hard
board. It is made in sheets in a wide variety of thicknesses but most commonly 1/8” to 1/4”.
It is made from wood but is more dense. Placed in water many hardboard products will sink
or barely float. It is hard on saws.
D3.4: Ironmongery
Ironmongery
D4.1: Types, Function and Construction of Foundations
FOUNDATIONS
FOUNDATIONS
The foundation is the part of the construction
where the base of the building meets the ground.
Function of a foundation is to transfer the structural loads
from a building safely into the ground. It also, anchors the
building and provides stability
TYPES OF FOUNDATIONS
Strip Foundations
Strip foundation as the name implies are continuous strips
of mass concrete or reinforced concrete or stone laid at a
pre-determined depth below ground level and along the
position of the load bearing walls only.
These types of walls are suitable for boundry walls,
retaining walls and domestic building not more than three
stories .
44
Details of the Cross section of a Strip
Foundation
Other types of Foundations
Raft foundation
This foundation consist of a
continuous reinforced concrete
slab under the whole building.
Using this type of foundation the
weight of the building is evenly
distributed across the area of the
foundation. For ordinary housing
purpose, a raft of 150mm – 250mm
thick reinforced concrete is sufficient.
Pad foundation
These may be circular, rectangular
Or square in section. The most
Common types are square. They
May be of mass or reinforces
concrete, but reinforced concrete
pads are reserved for large type
of structures. They are generally
used to support isolated loads
such as those in columns, piers
and heavy machinery in factories.
Pile Foundation
This type of foundation uses piles to transmitting load from
a building to a bearing stratum where such a stratum
underlies a depth of weak upper soil.
Foundation Components
(to attach wood stud sill plate)
(moves water away from
building)
(to keep water off of foundation wall)
(separates slab from foundation wall)
(to keep water off of slab)
(moves water away from building)
(to keep water off of slab & moisture barrier)
Site Preparation
•Remove trees and any debris
•Remove top soil (4-6” below surface)
Site Layout
•Ensure lot lines are known & setbacks are complete
•Layout building perimeter
•Use batter boards
•Establish building corners & building perimeter
•Use surveying instruments
Excavation
•Excavate foundation along line created by batter boards
•Excavate remainder of soil inside perimeter
•Don’t excavate inside soil if slab on grade
•If deep foundation, taper edges to prevent collapse
•If soil unstable, or very deep - use shoring
EXCAVATION AND TIMBERING TO TRENCHES
Excavation
•
The method of excavation can either be manual or
mechanical. Manual excavation is used extensively
on small domestic structures. The manual process
requires hand tools such as Pick Axe, Shovel/Spade,
Digging Bars, Forks, Hoes and Diggers.
Mechanical
•
Machines now perform the bulk of excavation on
major building projects. The principal machines
are: Dragline, Bulldozer, Front end loader and Back
hoe
Timbering To Trenches
•
Timbering is the temporary support used at sides of
trenches to prevent caving in. The support given to
the sides of the trench depends upon the depth of
the trench and the soil conditions. Weak soils will
require more elaborate temporary support.
Types of Timbering
•
Open Boarding – this is used for moderately firm
ground such as sandy gravel, soft dry chalk and firm
clay.
•
Poles and Struts – these are used for moderately
firm ground, such as stiff clay, firm gravel and hard
chalk. The poling boards are spaced 1.8 m apart.
•
Close Boarding or Sheeting – this is used for
unstable ground such as loose sand; wet soils and
made up grounds.
54
Module D5: Walls
Definition
A wall is a continuous, usually vertical, solid structure of brick ,stone, timber or metal
which encloses and protects a building or serves to divide buildings into compartments
or rooms
They carry and transmit to the foundations the imposed vertical loads from other
Building elements(beams, floors, and roofs) and ensure the stiffness of the whole
structure. They also protect the structure from the horizontal actions of wind and
earthquake, acting as wind bracing.
Walls are defined as external or internal to differentiate functional requirements, and
also as load bearing or non-load bearing to differentiate structural requirements.
Load bearing walls, those that carry imposed loads, such as those transmitted by
floors, roofs…;
Non-load bearing walls which can carry just their own weight and if they are made
of masonry are termed panel walls;
Non-load bearing walls supported by other structural elements, those related to a
framed structure
Functional requirements
• The function of a wall is to enclose and protect a building
or to divide space within the building. The main
functional requirements are:
• 1) Stability
• 2) Strength
• 3) Durability
• 4) Weather resistance
• 5) Fire resistance
• 6) Thermal insulation
• 7) Sound insulation
Bonding
• In building a wall of brick, it is usual to lay the bricks in some
regular pattern so that each brick overlaps partly two or more
bricks below itself. The bricks are said to be bonded, meaning
that they bind together by being laid across each other.
• Three types of bond, the patterns in which the bricks are laid,
are shown below:
English Bond
Flemish Bond
Stretcher Bond
Setting out openings in Walls
•
Once the wall reaches ground level thought must be given to the position of the
different openings. These openings are usually for doors, windows, frames and
arches.
The following terms are used when dealing with masonry:
1.
2.
3.
4.
5.
6.
Lintels: Steel reinforced- concrete beams used for support over
windows and doors
Laying Block: The process of mixing mortar, applying it to masonry
block, and placing the block to create walls.
Course: A row of masonry units
Masonry: Anything constructed of brick, stone, tile, or concrete unit held
in place with portland concrete
Concrete Sills: Used under windows and doors
Footer or Footing: A continuous slab of concrete which provides a solid,
level foundation for block or brick
Notes:
1.
2.
3.
4.
5.
6.
7.
Door openings will have 2" jambs on both sides and top.
Door will be a standard height (44" x 6'8").
Door sill will accommodate a concrete floor inside.
Window openings will accommodate standard size windows.
Space above the top of the door will accommodate appropriate trim under the eaves of the roof.
Reinforced concrete lintels carry the weight over door and window openings.
There are no cut block in the wall. Therefore, the wall can be built with a minimum of cost and labor.
A building front laid out using only whole and half block.
Procedure for laying blocks
•
•
A.
B.
•
C.
•
D.
E.
•
F.
•
G.
Spread a layer of mortar called a mortar bed as the footer.
Position the block on the mortar bed so that its outside corner rests
there the outside corner of the wall should be. Level the block by first
placing the level across the block and then lengthwise along the block.
Turn several stretcher blocks on end and apply mortar to the ears
with a wiping or swiping stroke of the trowel.
Lay several stretcher blocks in place by working away from the
end or corner block.
Use the end of the trowel handle to tap the block until each block
is plumb, level, and the course is straight.
Apply a mortar bed on top of the first course in preparation for the
second course.
If extra strength is needed in the wall, install reinforcement in the
mortar bed.
Procedure for laying blocks
•
•
H.
I.
•
J.
•
K.
•
L.
•
M.
As the block laying progresses, cut off excess mortar with the trowel.
Use a line to keep the courses straight. The line is positioned to
be level along the top of the block.
When a block must be cut, use a mason=s hammer and make
multiple strikes along the line to cut; then make one sharp strike
on the web.
Check the height to be sure each new course is an additional 8
inches high.
After the mortar dries and hardens slightly, finish the joints by
rubbing it with a broken piece of block.
If a joint other than a flush joint is desired, use a jointer to
compress the mortar and create a watertight joint. Tools are
available to create joints that are concave, v-shape, flush or
raked.
Showing procedure in laying concrete
block walls
The usual practice in applying mortar to
concrete blocks
A method of laying concrete blocks. Good workmanship
requires straight courses with the face of the wall plumb
and true.
Wall Framing
Wall framing is built upon the same sheathing module that
floor framing used – covered with sheets 48” by 96”. The
standard spacing for wall studs is 16” o.c. 15 1/4” must be
used at the beginning of marking out a wood frame wall.
Wall Framing
Wall framing is done with standard members for
the areas around openings, at corners, and at
intersecting partition walls.
What are the parts of a framed wall?
(Figures 1)
1) Sole plate
2) Stud – usually placed 16” or 24” o.c. (on
center
3) Cripple & trimmer studs – used in corners,
window and door openings
4) Header
5) Top plate
Material information
• What lumber sizes are used for the studs and
plates?
- 2 x 4’s or 2 x 6’s, depending upon climate
or desired insulation
• What lumber sizes are used for the headers?
- 2 x 10 or 2 x 12
Wall framing members
- cripple studs are shortened
studs that end because of
an opening
- trimmer studs are shortened
studs that support rough
openings and the weight of
the header
- headers carry the weight of a
building across rough
openings
Wall framing members (cont.)
(Figures 2)
- header length = rough
opening + width of trimmer
studs
- headers are required across
openings in load-bearing
partition walls
- headers are usually two
framing members nailed
together (w/ plywood or
insulation in between) to
equal a wall’s thickness
Plate Layout
(Figure 9 – 12)
• What is the first step of plate
layout?
- marking the location of
the studs
• Before the wall is nailed in
place, what needs to be
checked for?
- Always check for
square!
- Temporary bracing should be
installed to hold a wall in place
until it is sheathed
Interior wall partitions
• What can construction of interior walls begin?
- After completion of the exterior walls
- Load bearing partitions are installed first
Special considerations in framing
- The rough-in process will
require the drilling or notching
of studs – wooden bracing
may need to be installed

Why is the top plate doubled
in wall framing?
- Extra ceiling and rafter
support
- Other special framing may take
place with large windows or
cabinet soffits
Wall sheathing
- Should be completed before roof framing begins
 What materials are used in the sheathing of
exterior walls?
- plywood, house wrap, masonry materials
- House wrap is designed to cover cracks in wall
joints where air may travel through a building
Wall sheathing (cont.)
• What materials are
used to cover the
interior walls?
- drywall, paneling,
masonry materials
Partition Intersection
• Where partitions meet outside walls, it is essential that
they be solidly fastened. This requires extra framing
The framing must also be arranged so inside corners
provide a nailing surface for wall-covering material.
Several methods can be used to tie walls together and
provide the nailing surfaces needed.
1. Install extra studs in the outside wall. Attach the partition
to them
2. Insert blocking and nailers between the regular studs
3. Use blocking between the regular studs and attach
patented back-up clips to support inside wall coverings at
the inside corners.
Wall Framing
Openings for doors and
windows are built large
enough for the window or
door to be plumbed and
shimmed after installation.
A 36” wide door is typically
installed in a 38 ½” “Rough
Opening”. An 80” high door
is typically installed in a 83”
R.O. R.O. sizes are typically
shown on plans
Wall Framing
Walls are laid out by
marking the openings
(centerlines) and wall
intersections
(centerlines) first, and
then indicating the
opening edges. Then
16” (or 24”) lay out
lines are drawn. Any
full length studs which
fall inside the opening
become cripple studs
Wall Framing
Walls are held square
using either wood letin bracing, metal
bracing, or structural
sheathing. Choice
depends on how the
walls will be
assembled and lifted.
Wall Framing
When top wall is
complete, ceiling joists are
installed if the roof is built
with rafters. If the roof is
built with trusses, the
truss bottom chord will
serve as the ceiling
framing. Strongbacks
commonly used to keep
ceiling joists aligned.
Module D9: Stairs
Function of the stairs:
Stairs provide access from one floor of a building to another, they are also used for
emergency escape
Functions:
1. Riser – encloses the space between two consecutive treads in a flight. It also
gives support to the tread.
2. Tread – provides a platform for climbing the stair.
3. Headroom – the clear vertical height measured from the ceiling to the nosing of
the step which provides unobstructed access from floor to floor.
4. Handrail – provides support to the user when climbing or descending the stair.
5. Balustrade – provides protection to the sides of the stair so persons do not fall
off at a height.
6. Newel post – provides support for the handrail and the staircase.
Parts of a Timber Stairs