Table of Contents

PRELIMINARY SITE WORKS ................................................................................................. 1

Factors Affecting the Choice of a Site ........................................................................................ 1 Reasons for Stripping and Clearing a site ................................................................................... 4 Purpose of Hoarding ................................................................................................................... 5 Laying Out of a Small Building .................................................................................................. 7 Purposes of Temporary Shelter ................................................................................................. 11

The Building Site .................................................................................................................. 11 Reasons for Temporary Services .............................................................................................. 14

THE MANUFACTURING OF PORTLAND CEMENT ........................................................ 16

Portland Cement........................................................................................................................ 16 Characteristics of different Types of Cement ........................................................................... 16

The five common types of cement ........................................................................................ 16

Notable Behaviour of Concrete ................................................................................................ 17 Characteristics of Aggregates ................................................................................................... 18

Requirements of Aggregates ................................................................................................. 18 Types of Aggregates ............................................................................................................. 18

Importance of Proportioning or Batching ................................................................................. 19

The total weight of water in the concrete.................................................................................. 20 Some common mixes ................................................................................................................ 20

TIMBER AND TIMBER PRODUCTS .................................................................................... 23

Softwood and Hardwood Trees ................................................................................................ 24

Conversion of Timber ............................................................................................................... 26 Seasoning of Timber ................................................................................................................. 27 Moisture content ....................................................................................................................... 28

Timber Defects.......................................................................................................................... 29 Wood Preservation .................................................................................................................... 32

Production of Manufactured Boards ......................................................................................... 33 Lumber Classification ............................................................................................................... 36

FOUNDATIONS ......................................................................................................................... 36

Types of Foundations ................................................................................................................ 38 Excavation and Timbering ........................................................................................................ 44

Types of excavations............................................................................................................. 44

Reduced Level Excavation ......................................................................................................... 44

Trench and Pit Excavations ....................................................................................................... 44 Types of Excavation Machines ............................................................................................. 45

Timbering to Excavation ............................................................................................................ 47 Precautions .................................................................................................................................. 51 WALLS ........................................................................................................................................ 52

Definition .................................................................................................................................. 52 Categories of Walls ................................................................................................................... 52 Functional Requirements for Walls .......................................................................................... 52

Types of Walls: ..................................................................................................................... 52 Definition of a Scaffold ............................................................................................................ 59

Two Main Systems of Shoring ................................................................................................. 63

Functional Requirements .......................................................................................................... 65 Categories of Floors .................................................................................................................. 65 Floor members .......................................................................................................................... 68 Important Steps in Constructing a Timber Floor ...................................................................... 73

ROOFS ......................................................................................................................................... 74 Definition: ................................................................................................................................. 74 Functional Requirements .......................................................................................................... 74 Factors Determining Roof Shape & Design ............................................................................. 74 Roof Classifications .................................................................................................................. 74

Types of Roofs .......................................................................................................................... 74 Advantages of using Roof Trusses ........................................................................................... 78 Parts of a Roof .......................................................................................................................... 79

Technical Words for Parts of a Roof ........................................................................................ 79 DOORS ........................................................................................................................................ 80

Types of Doors .......................................................................................................................... 80

Door Ironmongery .................................................................................................................... 83 Door Dimensions ...................................................................................................................... 84

WINDOWS .................................................................................................................................. 85 Functions of Windows .............................................................................................................. 85 Building Regulations for Windows .......................................................................................... 85

Technical Terms for parts of a window and frame: .................................................................. 85 Types of Windows .................................................................................................................... 86

Some common terms associated with Stairs ............................................................................. 89

Building Regulations regarding Stairs ...................................................................................... 89

FINISHES .................................................................................................................................... 91 Rendering .................................................................................................................................. 91

Plastering................................................................................................................................... 91 Types of paints .......................................................................................................................... 92 Properties of Paints and Varnishes ........................................................................................... 93

Methods of Application ............................................................................................................ 93 The Purpose of Solvents ........................................................................................................... 93

RELATED SERVICES .............................................................................................................. 96 The Principles of Plumbing Pipes ............................................................................................. 96

Methods of Jointing and Fittings .............................................................................................. 97

The Principles of Drain Runs .................................................................................................... 99

THE BUILDING TEAM AND BUILDING TRADES .......................................................... 101 The Building Team ................................................................................................................. 102 Various Building Trades ......................................................................................................... 103

HISTORY OF BUILDINGS .................................................................................................... 104 Factors Influencing Building Designs .................................................................................... 104

Influence of Other Culture on Local Building Styles ............................................................. 104

1

PRELIMINARY SITE WORKS

Factors Affecting the Choice of a Site

Zoning

Zoning is the legal identification of land for a specific use. The general categories of

zoning are:

1. Residential

2. Commercial

3. Industrial

4. Agricultural

Zoning helps to assist land developers or owners in recognizing land for use as well as

provide information about the character of the neighbourhood. Lands within a zone may carry

different unit cost.

Land use

The owner or client must be sure that the land can be used for the intended purpose.

Although an area might be appropriately zoned, specific plots of lands may have certain

restrictions placed on them as a result of buried services or proposed development, e.g. roads,

gas lines etc.

Ownership

This is certified by a deed (legal document) which must be established before any final

decision is taken regarding any purchasing of land. Ownership transfer can only be made

between the rightful owner and the purchaser.

Boundaries

Boundaries must be established and supported by a survey drawing before the actual size

of the property can be ascertained. This task is usually carried out by a legal chartered surveyor.

Boundaries are normally marked in such a way that they can be easily identified or re-

established. References for markers are called Datum- Points.

Topography

Topography is the shape of the surface of the land. This shape is sometimes referred to

as ―contour‖ and can be classified as follows:

- flat

- undulating

- gently sloped

- steeply sloped

Access

All lands not immediately adjoining a street or public pathway requires some means of

access. This access influences movement on and off site during the construction stages as well

as during normal occupancy. Where the possibility of trespass exists, access should be legally

established and be adequate.

2

Shape

When purchasing a piece of land, the shape of the land should reflect the proposed shape

of the structure within the framework of the legal restrictions. Examples of problems commonly

encountered with lands are:

1. Too narrow

2. Corners may be too acute or there may be too many corners.

reinforcing steel

street possible building

limiting

position

(a) Narrow Lot

legal limits

(b) High unusable Land Space owing to a

number of and sharpness of corners

Size

Minimum sizes of building lots are usually specified in order that:

- Legal requirements of setback and off set distances are satisfied

- The building should occupy the maximum percentage of the total land area as specified

by the authorities for the prescribed zone.

- A reasonable sized building is produced.

History

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:

1. Water- whether a natural water course, springs or flooding are associated with the site.

2. Dump- whether the site was ever used as a dump.

3. Original topography- whether the land was ever filled.

4. Other problems e.g.

o Whether trees were recently removed to accommodate development or

o Underground lines such as electric, gas or telephone.

5. Development- This is a measure of clearing and preparation activities associated with a

site. It may also indicate the availability of services to the site.

Unit Cost

Unit cost is the price per metre or foot of the land. Unit cost is normally associated with:

1. Level of development

2. Available amenities

3. Available Services

3

4. Location

5. Zone

6. Demand

7. Topography

Amenities refer to the degree of comfort associated with the location, and are related to the

available utilities, health and educational facilities as well as other features such as public

transport, shopping centres and recreation facilities.

Location may influence the unit cost by providing certain advantages such as prevailing winds,

scenic views and general neighbourhood.

Sloping sites

4

Reasons for Stripping and Clearing a site

Stripping

This is the removal of the topsoil from the construction area. This area is usually stripped

to a depth of 150 mm, using a bulldozer.

Stripping helps to provide a sound level platform as well as the removal of vegetable

matter as well as the removal of termite‘s nests.

Soils containing high levels of vegetable matter tend to:

1. Support plant life

2. Be very unstable

3. Affects some building materials

Clearing

Clearing is not necessarily part of stripping but for undeveloped sites, clearing is

essential. Trees which sometimes obstruct the building process, those found to be in the way and

at a time obstruct the flow of traffic and must also be removed. The roots that would pose a

problem to the building process or even affect the foundation must be removed as well.

Other obstacles like derelict buildings should be removed, because they too hinder the

building process and can cause problems with the foundation.

5

Purpose of Hoarding

Hoarding is a part of the temporary facility installed on a construction site. Its primary

function is the enclosure of the construction area to serve as a form of protection to passers by.

This enclosure has other purposes and is developed accordingly.

Public Protection

The local authority has the responsibility for the protection of the public against injury

during any construction work. As such, there are laws requiring the installation of hoarding,

particularly where pedestrian traffic is common. Hoarding should provide protection from the

vertical side and overhead as well as permit or provide adequate lighting and ventilation if

required.

Security

The construction site must be secured, especially during evenings, on weekends and

public holidays.

Material Protection

Hoarding is an ideal way of ensuring some degree of protection against theft and

vandalism of materials and installations.

Control

The control of the movement of workers and avoidance of unwanted interruptions and

distractions assist in increasing productivity. All activities should be carried out with

minimum inconvenience. The movement of supply vehicles and receipt of goods should

be planned and controlled at all times.

To keep out stray animals

It is important that stray animals be kept off of the construction site since they can cause

disruptions to the building works as well as harm to the workers.

6

7

Laying Out of a Small Building

8

Building Layout

The Setting out of a building can be divided into two specific operations:

Establishing a datum peg and transferring required levels to various positions

Establishing the position of the building and setting up profiles (batter boards)

Establishing the position of the building and setting up profiles

The basic requirements for establishing the position of a building are linear measurement

(length), the setting out of right angles and the setting out of curves.

Linear Measurement

A 30m steel tape is most often used for setting out; linen or plastic tape should be

avoided as they are likely to stretch, and this could result in serious errors. If steel tapes are not

fully stretched out they can give inaccurate readings. Wherever linear measurements are made

the tape should be held horizontal. For sloping sites the possibility of error is far greater. For

slightly sloping grounds pegs of different lengths may be used. For steeper slopes the tape is held

horizontally and the measurement is plumbed down to the peg.

Setting out Angles

Right angles can be set out using any one of the following methods:

1. Using a builder‘s Square

2. Using Pythagoras‘s 3:4:5 rule

3. Using Site square

Setting out Curves

The methods used to set out a curve will depend on its size and whether its centre point is

accessible or not.

The four main methods are:

1. Timber template

2. The radius Rod

3. Triangular frame

4. Calculated ordinates

9

10

Layout Procedures for a Small Building

It is essential to obtain a working drawing of the proposed building before any work is

started. After careful study of this, the builder can then proceed with the layout of the building.

The procedures for setting out a small building are as follows:

1. The building line is established with reference to the setback distance from the centre line

of the road. The line is established by driving in 50mm x 50mm softwood pegs A and B

on or near the side boundaries. Position a nail in the top of the pegs to represent the exact

position of the building line. Strain a line between these two nails.

2. Drive two pegs C and D along the building line to indicate the front corners of the

building and with reference to the side setbacks as indicated on the Working drawing.

Drive nails into the top of the pegs to indicate the exact position of the corners on the

building line.

3. Set out lines at right angles to pegs C and D and establish pegs E and F. Drive nails into

the tops of pegs E and F to indicate the exact positions and strain lines between the four

pegs.

4. Measure along lines CE and DF to establish pegs G and H, the remaining corners of the

building.

Check lines should be used at this point to determine the accuracy of the layout and adjustments

made where required.

Profile boards can now be set up just clear of the trench runs at all corners and wall intersections

of the building. Ensure that there is adequate clearance space between the position of the trench

and profiles to prevent obstruction to profiles due to excavation procedures. Transfer positions

from the setting-out lines on the pegs to the profile boards. Step-off all trenches and block wall

widths and drive nails in these positions. Saw cuts can be used as an alternative to nailing.

Lines can be strained on the nails to indicate trench width and block wall width when

excavation and blocks are to be layed.

11

Purposes of Temporary Shelter

The Building Site

Site Preparations

Before any preparation work can commence the Building regulation/code should be

checked. This is necessary to ensure that the building (commercial or residential) to be erected

complies with the standards laid out in the code. There are zoning laws to be adhered to as they

relate to:

1. The building line

2. Distance Separation

3. Lot line

4. Premise

5. Property Line

6. Setback

7. Do a check on the Site Deed

8. Obtain a Building Permit

12

The Building Line-This is a legally determined boundary that no part of the building can cross.

Distance Separation- This describes the amount of open space between buildings. Open space

helps to keep fire from spreading from one structure to another and enable good ventilation.

Lot/Property Line- A surveyed and recorded boundary (or monument) that separates one piece

of property from another. In essence, it is the legal boundary that marks a lot or parcel of

property.

Premise- A term used to describe collectively a piece of property as well as any buildings or

structure on it.

Setback-This is the open space required between a building line and the street centre line. It

could also be used to describe the distance between the sides of a building the lot or rear

boundary lines of a property.

Site Investigation

The purpose of a Site Investigation is to determine before hand:

Existing trees and buildings on the property or adjacent property

Details such as full data of existing services or the lack of it

Contour lines- natural grade elevations

Details of above ground obstruction such as transmission lines

Topography of the site and existing fording (water running under ground)

Sewer system availability or the lack of it

The geographic location (with respect to the orientation)

Required Security and Staffing

Layout (General site conditions such as soil nature, height of water table, flooding risks, and

neighbouring properties, among others).

These factors will to a large extent help the builder in the design and construction processes

of the proposed work.

Soil Investigations

Determines the suitability of the site for the proposed project

Determine an adequate and economical foundation design.

Determine the difficulties that may arise during the construction process and period.

Determine the occurrence and /or causes of all changes in subsoil conditions

Site Preparation Principles

In Site Preparation the builder will require operatives, materials and plant, which must be

carefully controlled so that the operatives have the right machines in the most advantageous

positions, the materials stored in such a way that will allow for easy access and little or no

interference with site circulation, and adequate storage space and site accommodation.

When Planning the Site Layout the following must be taken into consideration:

13

1. Site activities;

2. Efficiency;

3. Movement;

4. Control ;

5. Facilities for health, safety and welfare provision, and

6. Accommodation for staff and storage of materials.

Usually before the proposed site is planned and drawn the prevailing conditions should

be considered these are; the condition and positions of existing roads and the setting out of any

temporary roads considered necessary should be noted and planned. Information regarding the

soil conditions, height of water table and local weather patterns should be obtained preferably

from the meteorological office or from the local authority.

Temporary Shelters

These are required on a building site for the housing of personnel, services, processes and

materials for the expediting and control of building works, and to cater for illness and accidents

among workers. Consideration should be given to the following:

Statutory Requirements

The construction site is under the control of the factory inspectorate and as such should

carry provisions for amenities to workers. Amenities usually include a change room, a lunch

room and sanitary facilities.

Activity Areas

Offices: Normally for large projects site offices and briefing rooms are provided to assist in the

daily administration of the project.

Workshops: Carpenters, steel benders and some other tradesmen require workshop facilities to

assist in their work. Workshops should be so located as to ensure good control and effective

handling of materials.

Storage

Warehousing: Warehouses are normally required for storage of delicate components and

fittings. Items normally stored in a warehouse include doors, windows, ceramic receptacles,

light fittings, electrical and plumbing appliances etc.

Tools and Equipments Stores: Tradesmen are usually required to carry and secure their own

tools. The main contractor, for special processes may find it necessary to carry a supply of

special tools and equipment which would be available to workmen. The store may also carry

other items that can only be had on special issue. Some of these items are paints, locks and small

tools. Such stores are controlled by a storekeeper or a timekeeper.

Material Stores: Material stores may be provided to protect materials from theft or damage. The

material stores are usually close to the appropriate workshop or activity area. Such stores would

carry materials such as reinforcing steel, rough lumber and cement. Special provisions must be

made to ensure that materials are not spoiled or damaged during storage and handling. In

addition, brittle materials such as tiles require provisions.

14

Reasons for Temporary Services

Temporary services relate to the provision of utilities for the purpose of facilitating

construction activities as well as providing conveniences for workers. The supplies normally

include gas, water, compressed air, electricity and telephone.

Conveniences

These include conveniences for personnel and work process.

Personnel: Provision under the factories act allows for provision of certain conveniences for

workers. Temporary services assist in the provision of drinking water, adequate lighting and

toilet facilities. Drinking water and toilet facilities should be positioned for quick access thus

reducing idle time.

Work processes: Utilities supplied 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:

A. Air- Pneumatic tools and equipment

B. Oil and Gas- Turbine and hydraulic tools and equipment

C. Electricity- electric tools and equipment

Heat, water and air are used in the following processes:

1. Heat- asphaltic processes

15

2. Water- making concrete

3. Air- Spray painting, excavating, compacting

Communication

Communication includes physical and verbal contact between the agencies and processes

during the life of the project. Factors to be considered in communication are temporary roads for

access to the site and storage areas, as well as possible telephone or two way radio contacts for

placing orders and dealing with routing administration and contingencies which are important.

16

THE MANUFACTURING OF PORTLAND CEMENT

Cement is a substance that binds aggregates together into a very dense material that possesses

great compressive strength.

Portland Cement

Portland cement is used in the manufacturing of concrete and mortar. It may also be used

as a bed for clay and cement tiles. Ordinary Portland Cement is made by mixing ground chalk or

limestone and clay with water to form a semi-liquid mixture, or slurry. Local materials such as

shale may be used instead of clay in the manufacturing of Portland Cement. The slurry is

screened and is passed into a storage tank where it is kept agitated in preparation for passage into

a kiln, which is a rotating cylinder, approx. 90 meters long, inclined at an angle and fired by

pulverized coal or oil.

The slurry is fed into the upper end of the kiln and flows down to the direction of the

heat. As the kiln revolves, it dries the slurry. Water evaporates under this intense temperature

heat (raised to about 1500 Celsius) fusing the materials into a clinker or cement noodles. The

clinker is cooled and ground to a fine powder. A small amount of gypsum is added to retard the

setting time of the cement.

Characteristics of different Types of Cement

Portland Cement is the most commonly used cement since it hardens rapidly. There are

several other cements that can be used for special purposes.

The ratio of Portland Cement to aggregates varies with the strength requirements for the

concrete. Additives may be put into the mixture or cement to enhance the strength or provides

additional qualities such as quicker drying, waterproofing, resistance to sulphate corrosion etc.

During the manufacturing of cement, various chemical components are produced. This

compound which influences the properties and behaviour of the cement includes:

(1) Strength Development:

(2) Setting Time and Heat Production

By varying the components, the properties can be modified. These properties can

influence the ability of the cement to resist sulphate attack, which is the rate at which cements

sets and heat is produced.

Some types of cements are low heat (used for concreting large masses) and some high heat (for

cold weather conditions).

The five common types of cement used in construction are Types 1, 2, 3, 4, 5

Type 1- Normal

This type is ordinary Portland Cement. It has normal qualities, a reasonable setting time

and is used for general concrete work, when conditions are normal. Such example include:

masonry work, filling of pockets, and ordinary strip foundation.

Type 2 – Moderate

This type of cement gives off less heat than type 1, and has a moderate resistance to

sulphate. It is suitable for use in foundations where there are low levels of sulphate but

17

offers good resistance to soils with high sulphate level such as those adjacent to chemical

plants.

Type 3 - Low Heat

This type is ideal for use in mass concrete work, such as large foundations or dam

retaining walls. It develops strength slowly and generates less heat, thus reducing

cracking.

Type 4 - High Early Strength/Rapid Hardening

This type is used when the weather is bad (rainy season), or when formwork has to be

removed early. It develops strength earlier than types 1 and 2.

Type 5 – Aluminium

This type contains aluminium ore. It is darker in colour than Normal Portland Cement. It

hardens very rapidly and has great strength.

Notable Behaviour of Concrete

Climatic conditions can influence the setting time of concrete and its‘ used. For

maximum strength development, concrete should be wetted down for 28 days.

18

Characteristics of Aggregates

Aggregates generally make up the bulk of the concrete. These are available in fine and

coarse grades. For mortar the size of aggregates is very small ranging from 0-4mm, and for

general concrete work the size varies from 5-20mm.

Requirements of Aggregates

All aggregates should be:

clean

free from sediments

sound

strong – not easily crushed

well graded

well shaped

Types of Aggregates

Coarse Aggregate

Gravel – This consist 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 banks, river beds).

Crushed Stones – Trap rock is the hardest and most durable stone that can be crushed and used

for making concrete. This stone is dark, heavy and close-grained, and is of igneous origin.

Granite makes good crushed stone and is less expensive than trap rock. The stone should be

graded in sizes 6mm-20mm.

Fine Aggregates

For concrete work these are sand, crushed stones or gravel screening. The most important

of these is sand. Sand is a fine divided material of rock which will pass through a standard 5mm

sieve. Sand is not subjected to disintegration, decay or expansion.

19

Importance of Proportioning or Batching

Proportioning aids in determining the strength, durability, permeability, workability and

economy of the concrete. Proportioning is essential to ensure a good mix.

Batching is the determination of the exact amount of each ingredient that is placed into a

specific concrete mix.

The following are some results of Batching.

Strength– In order to obtain maximum strength, the aggregates must produce little or no

voids in the concrete. This increases the density of the concrete thus increase its strength.

Economy– Cost is a major factor in concrete work. Cost is influenced by careless use of

ingredients. The most costly ingredient is 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 worked with ease. This

property is enhanced by the correct proportioning of the cement and aggregates and water-

cement ratio.

Volume Batching

This is generally used but it is a less accurate method of mixing concrete. A measuring

box is used to determine the amount of cement and aggregates. A change in the moisture

content will impact upon the volume of the materials and affect the quality of the concrete.

Figure 2 showing a diagram of a Gauge or Measuring Box

Batching by Weight

In this method the materials are measured by weight. This is a more reliable system of

batching than that of volume. Variation in volumes owing to compacting is eliminated when

using this method.

20

Water

The water used in the making of concrete must be clean and free from impurities which

could affect the quality of the concrete. A proportion of water will set up a chemical reaction that

will harden the cement. The rest is required to give the mix workability and will evaporate from

the mix while it is curing. An excess amount of water will give a porous concrete or reduced

durability and strength.

The water/cement ratio is the amount of water used in the mix and is expressed as:

The total weight of water in the concrete

Weight of cement

For most mixes, the ratio is between 0.4 and 0.7. Concrete mixes can be expressed as volume

ratios, thus:

1:2:4 = 1 part cement 2 parts fine aggregates and 4 parts coarse aggregates

1:5 = 1 part cement and 5 parts all in aggregates

Some common mixes –

1: 10 = not a strong mix but it is suitable for filling weak pockets in excavation and for binding

layers 1:8 = slightly better – suitable for paths and paving

1:6 = a strong mix suitable for mass concrete

1:3:6 = the weakest mix

1:2:4 = the strongest mix suitable for reinforced concrete

Concrete is a mixture of fine aggregates, coarse aggregates, cement and water that possesses

great compressive strength.

Mortar is a mixture of cement, sand and water in definite proportion.

Slump test

21

PROPERTIES OF PLASTICS

Plastic is one of the new building Materials being widely used in the Building Industry

and for Domestic Purposes. Such purposes include: - plumbing, electrical fittings and sanitary

appliances. Plastics are usually by products of Petro-Chemicals.

Plastics are usually:-

light weight

easily handled

durable

strong for their weight

readily adapted to various situations

Properties of Plastics which make them suitable for usage in Construction Work are:

1. strong

2. light weight

3. durable

4. pliable/flexible

5. easily joined

6. glazable

7. elastic

8. water proof

9. rust proof

10. cheap/economical

11. soft

Some disadvantages of plastics and precautions to be observed in their use are they:

Can be easily damaged if not properly protected

Have a low melting point

Are easy to crushed under weight

Must be supported when suspended

Have poor chemical resistance to thinners and solvents

Becomes brittle under continuous exposure to variations of weather

Types of Plastics

Application

1. Thermo-Plastics

Conduits, pressure and non-pressure pipes

2. Polyvinyl

Tiles, mouldings

3. Polythene

Sheeting, bags

4. Nylon

Ropes, coverings, garments

5. Thermo-setting Resins

22

Uses of Plastics in the Building Construction Industry are:

1. Electrical insulation

2. Conduits

3. Guttering

4. Tiles/Floor Finishes

5. Damp Proof Membrane

23

TIMBER AND TIMBER PRODUCTS

Bark - Every species of tree has its own bark which is a means of identification. The

bark is the outer layer of a tree that protects it. Without it the tree cannot survive.

Cambium layer - This is the growing part of the trunk. Here new cells are constantly

developing. Some becoming bark while others become wood.

Medullar Rays - Food is distributed to all parts of the tree by means of these small cells. These

wood cells grow in length radially and can be easily seen in oak, beech, and mahogany.

Annual Rings - The age of the tree can be determined by the counting of these rings, as each

ring represents one year of growth.

Pith or Medulla - This is the core of the tree. It may be sound or solid, but in many cases it is

filled with a cork like substance. It has a dark, brown colour.

Sapwood - Light coloured outer concentric rings of woody tissue that is found next to the

cambium. It contains only a few living cells and functions mainly in the storage of plant food.

Its thickness varies from 13mm to as much 150mm in some species.

Heart wood – The inner concentric rings of woody tissue which consists of inactive cells.

These cells of heartwood may contain many minerals which contribute to its darker colour, great

beauty and resistance.

Bast - The channel that is found between the cambium layer and bark which transport food from

the root to the leaf.

24

The tree can be regarded as one of nature‘s gift to man. It provides food, shelter and fuel.

The tree is a living organism, the components parts performing specific ―life‖ functions.

Timber is the oldest building material. The growth process of certain species encourages

the production of various by-products.

To those studying botany a tree is just another plant. To the carpenter and the joiner it is

the plant which produces the material with which he is mainly concerned namely wood or

(timber). The growth of a tree is affected by the soil and by the climate in which it grows.

Softwood and Hardwood Trees

Commercial timbers are classified into soft woods and hard woods. The most common

method of identifying them is by their leaf. Soft woods have narrow needle like leaves where as

hard woods have a broad leaf.

Softwoods

Soft woods (gymnosperms) are not all soft; some soft woods are very hard e.g. Yew,

pitch pine strong and durable. Soft woods are all for practical purposes, derived from a group of

trees called conifers. Coniferous trees are mainly evergreen and grow chiefly in the northern

cold to temperate zone. Soft woods comprise about 75% of the timber used in the U.K.

Soft woods are non- flowering and have needle shaped leaves and naked seeds contained in

cones, their branches normally arises in whorls with more than two at the same level. Even after

the tree is converted, most lumber can be easily identified as hard wood or soft wood. Conifers

are simpler and more uniformed in structure than broad leaved trees. They have mainly one type

of cell, the tracheid. These cells appear as regular rows of holes, with the cells formed during

spring and summer (wet seasons) having thin walls and those formed during autumn and winter

(dry seasons) have thick walls. It is this difference in the formation of cells that indicates a

year‘s growth or annual rings.

Soft woods main features include:

1. They have an open grain texture, which is easier to work on than hard wood.

2. They have a lighter colour than hard wood.

3. They do not shed their leaves seasonally.

4. Their leaves are usually needle or cone shaped.

5. They grow quite quickly.

6. The timber produced needs to be protected from the weather by applying paint, varnish or

preservatives.

7. They need to be protected from insect attack.

Examples of soft woods are:

Douglas fir

Western red cedar

Pitch pine

White pine

Red wood

Red pine

Sugar pine

Southern pine

Yellow pine

Caribbean Pine

Alaska cedar

Honduras cedar

25

Hardwoods

Hard woods (angiosperms) are not all hard, some hard woods are very soft e.g. balsa.

Most hardwoods are deciduous or broad-leaved trees. Hard woods include densest, strongest,

and most durable timbers. Some hard woods contain resins and oil which interfere with the

hardening of paint such as teak. The cheapest hard woods approximate in cost to the more costly

soft woods.

Hard woods can be recognized by their broad leaves on their branches which usually

grow out at different levels, at the most two at the same level. These trees produce flowers from

which their seeds come enclosed in a fruit. These trees grow in cool to tropical climates and may

be deciduous or evergreen.

Hard woods unlike soft woods have a more complex structure with mainly two distinct

cells. One type is fibrous and similar to the tracheid and the other type is known as vessel or

pore cells. The latter appears as pores or holes in the end grain, and as vessel lines on

longitudinal surfaces.

Cell structure in both soft woods and hard woods affect the grain, texture, density and

figure in these woods. The grain in soft wood is generally straight, the texture is fine and the

figure is plain to pleasing. In hard woods, the grain may be straight, sloping or interlocked. The

texture is fine to coarse because of the size and arrangement of the pores and the figure plain to

highly figured. These are dense hard boards and more difficult to work with tools.

Hard wood’s main features include:

1. They are harder to work with hand tools than soft wood trees.

2. They are darker in colour or have distinctive colours.

3. They shed their leaves seasonally.

4. They are slow growing and cannot be cultivated.

5. They are more expensive to use for timber.

6. They are selected for decorative appearance.

Examples of hard woods are:

Mahogany

Tamarind

Teak

Mora

Green heart

Bullet wood

Satin wood

Mahoe

Crab wood

Wallaba

Cedar

Oak

Birch

Beech

Balsa

26

Conversion of Timber

Conversion is the process of cutting up timber in marketable sizes. It is a common

feature that ―decorative‖ cuts are made during conversion. The two general methods of selling

lumber are plain sawing, (flat or slash sawing) and quarter sawing.

Plain Sawing

The log is slabbed on either two or four sides to form a cant from which other plain

sawed lumber is cut. Plain sawed lumber has several advantages over quarter sawed:

1. More lumber is produced when grain figures are not considered.

2. It dries more rapidly.

3. It is cheaper to cut.

4. It has lower unit cost.

Plain sawing (1,2,3,4) and quarter sawing (5,6)

27

Quarter Sawing

Quarter sawing can be done any of four methods: radial, tangential, combined radial

tangential and quarter tangential.

Quarter sawing has the following advantages:

1. Fewer tendencies to warp or twist.

2. Fewer tendencies to cut or twist.

3. Less shrinkage.

4. More durability strength.

5. More attractive grain pattern.

6. More rapid kiln drying.

It is used in the manufacture of high class joinery, furniture and quality work. It wears more

evenly when used as flooring.

Disadvantage

The method of conversion is time consuming and produces much waste.

Seasoning of Timber

Timber cannot be used for carpentry and joinery immediately after it is converted, since

there is a lot of moisture present in the wood. A large portion of this sap must be removed, if

distortion resulting from shrinkage is to be avoided. The process of moisture removal from the

wood is called seasoning. This can be done in either one of two ways: natural or artificial terms

known also as curing or conditioning. It is realized that, the lower the moisture content in the

wood the greater its strength.

Natural Seasoning

After conversion, the wet timber is stacked with strips of wood, usually of the same kind,

or stickers separating each layer. This allows proper circulation of air which removes the

moisture. A suitable roof is needed to protect the timber from sun and rain. Air seasoning

reduced the moisture content to about 17% under ideal conditions and even takes up to two

years. The moisture content must be in equilibrium with that of the atmosphere. The weather

and thickness of the material will vary the length of time required for seasoning. End splits may

be controlled by tacking on straps or metal or wood, or by putting paint wax or oil on the ends of

the boards.

28

Advantages

- High quality of lumber.

Disadvantages

- Length of time, limited availability of large quantities.

- May be more costly

- Needs more space for drying

- No control over drying process.

Artificial Seasoning

Artificial seasoning has improved greatly and the kiln which is the storage house for it

can now be completely computerized to control the drying process even without attendance or

human inspection. Accurate moisture content readings are readily available at any time. The

materials are stacked in a similar manner of that of the natural.

Advantages

- Relatively short time

- Early use of material

- May result in greater availability and reduced cost.

- Some wood worms are destroyed by the heat

- Moisture content can be controlled to as low as 12%

Disadvantages

- Case Hardening

- Rapid drying can cause it to check or become honey combed.

Moisture content

When a tree is felled it contains a great deal of moisture. The timber will need to have

some moisture content, whatever its commercial use is to be. The purpose of drying the timber

is to minimize the subsequent movement when it is used; which means, different uses demands

different moisture content levels. The timber for internal use should have lower moisture content

than timber which is used externally. This is because internal timber would be reduced by the

29

warmth of the atmosphere. This can cause excessive shrinkage and possibly other more serious

defects.

Moisture content is always expressed as a percentage of the dry weight of the timber.

The formula used to calculate this formula is:

Wet weight- Dry weight x 100

Dry weight

= moisture content (%)

A sample of timber is cut and weighed. This is the wet weight. It is placed in a kiln 100°C and

taken out at intervals until no further weight is loss. This is the dry weight. A piece of timber

weighs 132.5g

Its dry weight is 108.7g

Moisture content weighs 23.8g

% of moisture (23.8/108.7) x 100= 21.9%

Example:

132.5- 108.7

23.8 x100

108.7

= 21.9%

Timber Defects

A defect is a fault in the timber that will result in some reduction in strength, appearance

which is usually cause by natural elements during growth or during conversion and seasoning

which could and should be avoided.

Natural defects

Knots are caused by branches growing out of the tree in which case the grain in the tree

trunk becomes twisted. Forest grown tree usually have less knot because of lack of sunlight.

The branches always start at the centre of the tree at the pith.

Sound Knots

They will not fall out of the position they occupy but they tend to crack. This allows the

inlet of fungus to attack the wood. Provided that they are not too large or close to the edge they

don‘t posed a problem.

30

Dead Knots

These are a source of real weakness, whatever is the size. They are produced when a

branch is broken off before the tree is finish growing. The tree starved this broken off part of the

trunk causing it to die. It is identified by a very dark colour around the decayed knot, making it

liable to fall out eventually leaving a knot hole. Such a timber is classified as low grade and is

unsuitable for structural use.

Shakes- Take the form of splits in the wood and detracts from its strength quite considerably.

Heart Shake- These occur in the heart wood of a tree when it is left too long after it has matured

before being felled for use. It is due to lack of food.

Checks- These are separation of the wood fibres along the grain. They usually occur along the

ends of lumber. In artificial seasoning checks are caused by rapid drying.

31

Ring Shake- These follow the contour of the growth ring. They usually result from excessive

swaying of the tree in high winds bringing about separation of the fibres.

Cup Shake- These are brought about by similar conditions as ring shakes, but without results.

They also position themselves in the growth rings.

Star Shake- These are fine cracks in the appearance of a star as a result of the sun drying up the

cellular tissue, when the bark has been damaged or when the timber has been season too quickly.

Dry Rot- This is caused by a fungus (merious lacrymans) a growth which lives in the wood and

destroys it. It thrives on wood in dark, damp unventilated conditions causing it to dry up and

disintegrate into dust.

Wet Rot- Wet rot (cellar) fungus attacks only wet timber, and is found in damp, poorly

ventilated cellars. The disintegration of timber is due to exposure to alternate wet and dry

weather which is favourable conditions for growth of fungus.

Up Sets- This is a form of shake, the cause of which is uncertain. The effect of it is in a zigzag

crack across the grain, where the affected boards are likely to snap very easily under little

pressure. Probable causes are:

1. The tree being struck by lightning during growth.

2. The tree falling awkwardly when felled causing a fracture to run through the log.

32

Bowing- This often results when the boards are stacked with too much distance between the

sticks.

Warp- This is any distortion from the true form and may include any one or a combination of the

following: cup, bow, twist. This is caused by the exposure to the elements and poor stacking in

the process of seasoning and usage.

Cupping

Spring Twist

Wood Preservation

Timber for construction work should be treated in order to increase its ability to resist

fungal and insect attack. Insects break down the cellular structure of the wood and destroy it‘s

strength and appearance. Timber being exposed needs to be protected.

Timber preservation is costly, extending to the life of the timber. Preservation is cheaper in long

term.

Some preservatives, such as creosote are used exclusively underground or in roofs where

the material will not be visible. Other types have pleasing effects, example: Cuprinol, ‗Atlas A‘

which change the colour of the wood to a light green.

Application requires some care since preservatives are highly toxic and others may attack the

skin.

There are three groups of preservatives:

1. Tar- oil type

2. Water solution type

3. Organic solvent type

Tar-oil

These preservatives are distilled from coal tar. Creosote is probably the best know. They

are very efficient but have a strong odour. This can be done by steeping or can be brushed on,

where the lumber becomes saturated after a period of time. It becomes resistant to insect attack

and moisture penetration.

Water Solution

33

Water is used as a vehicle to take the chemical into the timber and afterwards it evaporate

leaving the chemical to fight off attack from sodium fluoride, zinc chloride and copper sulphate

solutions which are commonly used as preservatives but are odourless and can be painted over

quite easily.

Organic Solvents

This can be done as non-pressure and pressure impregnation.

Pressure Treatment

This is done by forcing liquid Wolman Salt under pressure into the timber- this ensures

better penetration.

Non-Pressure

Brushing- A suitable material is brushed on the lumber. This is a simple process but slow to

allow the liquid to soak in.

Spraying- This is used in areas difficult to get into, such as roof spaces. It is much quicker and

effective than brushing while using a spray gun.

Dipping- The timbers are submerged in a bath of preserving liquid for 5-15 minutes. Excess

preservatives are allowed to drain into the bath which can produce fairly good results.

Steeping- Similar to dipping, however, the timbers are left submerged for at least (2) weeks

especially with solution types of preservatives.

Production of Manufactured Boards

Ranges of sheet material are widely used in woodworking and building industries. Some

are made from solid timber while others are made from low-grade timber. Standard size for

building boards is 1220 x 2440 mm. Thickness varies according to use.

34

1 laminboard

2 core

3 blockboard

4 battenboard

5 cellular board, cellular plywood

6 composite board

7 hardwood plywood

8 mixed plywood

9 softwood plywood

35

10 multi-ply

11 crossbanding

12 star formation

13 parallel-grain plies

14 single layer chipboard, standard grade chipboard

15 multilayer chipboard

16 peg board, perforated hardboard

17 hardboard

Plywood

Plywood is one the most extensively used boards which is made up of an unequal number

of sheets and veneers called plies. Three- ply plywood consists of three veneer of equal

thickness glued together with the centre or core veneer, having its grain running at right angles to

the outer veneers. This gives it considerable strength. It has extensive uses which may include

panelling and lining as well as other forms of covering. The grade is usually stamped on the

board by the manufacturer and these must be recognized when deciding the usage of the board.

Int - Denotes for internal use only and indicates that is has been glued together with glue having

low moisture resistance. If such timber is exposed to moist conditions there would a separation

of the veneers.

MR - Fair resistance to moisture.

BR- High resistance in exposed conditions because it is boil resistant.

WBP- Indicates that it is weather and boil condition and also in the boat building industry.

Laminated Panels

These panels are constructed of thin layers of material glued together to form special

effects. These panels will resist warping and shrinkage.

Hard Boards

This is yet another of the wood waste product. Hard board are made from wood chips

and logs. The wood is pulped by machine, and bonded with adhesive and finally pressed to a

thickness of 3mm- 6mm. With such a thickness they usually have a width of 1.2m. With lengths

of 2.4 – 3 m. Their usage includes panelling, wall and floor covering.

Bagasse Board

Bagasse is the residue left after milling cane during the manufacture of sugar. The

material is crushed to a pulp, mixed with adhesive and compressed with a heat treatment. This

results in a hard durable board suitable for interior work.

Chip Board

This board makes use of machine chips of wood, glued and compressed into large sheets.

The core section consists of larger chips than the surface. A disadvantage is that it is unable to

take a screw. It is used for cheaper range of furniture as well as wall coverings.

36

Lumber Classification

Lumber is sold by standard cubic measurement, board measure.

Any size over 30mm and 100mm is boards. (31mm thick and 100mm wide)

37mm thick is planks

Measurement in length is called linear.

Measurement in length and breath is called square measure.

Measurement in length, breadth and thickness is called cube measure.

―N‖- Number of pieces in stock.

―T‖- Thickness in mm.

―L‖- Length in metre.

Note:

- 1 inch=25.44mm

- 1 foot = 304.8mm

- 1 metre = 3.281ft

Formula to calculate board in m is:

Foot board measure 10 pieces of 2‖ x 6‘ x 12‘0

= 10 x 2 x 6 x 12‘ 0

12

= 120 FBM

L (M) x W mm x T mm = m3

1000 1000

If L = 5m W = 175mm T= 5mm

Then volume of board or lumber =

5 x 175 x 25

1000 1000

= 0.02m3

37

FOUNDATIONS

The purpose of the foundations is to adequately transfer the load of a structure to suitable

ground and to spread building loads over a sufficient area of soil to avoid undue settlement,

particularly unequal settlement.

Foundations should meet the following requirements;

(1) Building loads must be supported and transmitted to the ground,

(a) safely; transmit and sustain to the ground the total dead and imposed loads so as

not to cause any settlement or

(b) without causing deflection or deformation of the building;

(c) without affecting adjacent buildings.

(2) They must be of such depth or be so constructed as to avoid damage by shrinkage of the

subsoil.

(3) They must be capable of resisting chemicals in the sub-soil.

The explanation of common terms associated with soils in foundation work is given below:

Settlement: Ground movement, which may be caused by:

(a) deformation of the soil due to imposed loads.

(b) volume changes of the soil as a result of seasonal conditions.

(c) mass movement of the ground unstable areas.

Made Ground: Refuse, excavated rock or soil deposited for the purpose of filling in a

depression or for raising the site above its natural level.

Bearing Pressure: The pressure produced on the ground by the loads.

Bearing Capacity: Safe load per unit area which the ground can carry.

Back Fill: Lateral excavated from site and if suitable used to fill in around the walls and

foundations.

Sub-Soil: Sub-soil lies below the topsoil to a depth about 300 mm.

38

Types of Foundations

The types of foundations normally used in construction include strip, raft, short bore pile

and pad. Various types of foundations are used in domestic buildings. The type of foundations

selected depends main~ on two factors:

(1) The total load of the building ("live‖ and "dead" loads).

(2) The nature and bearing capacity of the subsoil.

(3) The design of the building.

Strip Foundation:

The majority of domestic structures have a strip foundation in which a continuous strip of

concrete provides a continuous support under load-bearing walls. This type of foundation is

composed of plain concrete usually to a mix 1: 3: 6 volumes (1 part cement, 3 parts sand 6 parts

coarse aggregate). The thickness of the foundation must not be less than the projection (P) and in

no case less than 150 mm. Reinforcement bars are sometimes used in small domestic building.

These bars strengthen the structure, and make it less vulnerable to earth tremors.

Strip Foundation

39

Wide Strip Foundation

Where the load bearing capacity of the ground is low, as for example marshy ground, soft

clay and made-up ground, wide strip foundations may be used to spread the load over a large

area of soil. It is usual to provide transverse reinforcement in the base of the footing to withstand

tensions that will arise. This is usually placed near the bottom of the footing. The depth below

ground level should be the same as for normal strip foundations. All reinforcements should be

lapped at the corners and junctions.

Deep-strip Foundations

These foundations are used in shrinkable clay soils (to reduce the cost of normal strip

foundation) in depths of 900 mm or more, and to counteract the variable soil conditions in

different seasons. In reducing the width of the foundation trench, the quantity of excavation,

backfill and surplus, soil-.removal is also reduced. The deeper foundation also provides greater

resistance to fracture from unequal settlement (by increasing the load bearing strength of the

section).

Deep Strip Foundation

40

Raft Foundation

Raft foundations cover the entire area of the building and usually extend beyond it. They

consist primarily of a reinforced concrete slab up to 330 mm thick, which is often thickened

under load bearing walls. The level of the base of the raft is usually within 300 mm of the surface

of the ground and the reinforcement is often in the form of two layers of fabric reinforcement,

one being near the top and one near the bottom of the slab.

The reinforcement helps to spread the loads and resist tensile stress, which could cause

cracking of the raft.

Raft foundations are best suited for use on soft natural ground or fill, or on ground that is

liable to subsidence as in mining areas. The ground at the edge of the raft should be protected

from weather, which can cause erosion or slippage. This can be overcome by:

(1) Laying concrete paving around the building

(2) Deepening the edge beam

(3) Laying a field drain in a trench filled with suitable fill as shown

Raft foundation

41

Stepped Foundation

On a sloping site the most economic procedure is to use a stepped foundation thus

reducing the amount of excavation, back fill, surplus soil removal and trench timbering. The

foundation is stepped to follow the line of the ground and the depth of each step is usually 150 or

225 mm (multiple of brick courses).

The lap of concrete at the step should not be less than 300 mm. The damp proof course

may also be stepped in a similar manner. Where the slope exceeds one in tenth it is desirab1e to

use short bored pile to overcome the sliding tendency.

Stepped foundation

42

Short Bored Pile

Short bored piles were devised to provide economical and satisfactory foundations' for

houses built on shrinkable clay. They consist of a series of short concrete pile cast in holes bored

in the ground and joined or connected (for load bearing walls) by light beams usually of

reinforced concrete. They have several, advantages over strip foundations:

i. speed of construction

ii. reduced quantity of surplus excavated soil

iii. ability to proceed with construction in bad weather

Problems do, however, arise on stony sites or where there are many tree roots.

Holes are normally bored to a depth of 2.5 - 3.5 metres by hand or mechanically operated

auger keeping the holes vertical and on the centre 1ine of the beams. The depth will be

determined by the stability and bearing capacity of the clay.

The piles, generally about 300-350 mm in diameter, should be cast immediately after the

holes have been bored. A mixture of 1:2:4 concrete is generally used. Short lengths 20 mm

diameter reinforcing bars should be set in the top of each corner pile and bent over to cast in with

the beams. The reinforced concrete beams often 300 x 150 mm' in section, are usually cast in

formwork, but in some cases are cast in trenches.

The placement of piles is influenced by the shape of the building, the load to be carried

and the load-bearing capacity of the piles. With load bearing walls, piles should be provided at

corners and junctions of walls, with intervening piles placed to give uniform loading and, as far

as possible, to keep ground floor door and window openings mid-way between piles.

Short bored pile foundation

43

Pad Foundation Pad foundations are isolated foundations designed to support columns. The area of

foundation is determined by dividing the column load plus the weight of the foundation by the

allowable bearing capacity of the ground. The thickness of the foundation must not be less than

the projection from the column (unless reinforced) and must, in any case I not be less than 150

mm. The size of foundation can be reduced by providing steel reinforcement towards the bottom

of the foundation running in both directions.

Pad foundation

The area of the pad for a foundation may be calculated by determining the ratio of the load to the

bearing capacity of the soils under laying the structure.

Terminology

Three terms used regularly with foundation construction are explained.

Footing: offsets at the base of a wall to provide a greater bearing area.

Damp proofing: making waterproof by special materials or processes.

Hardcore: broken bricks block or stone consolidated as a foundation for concrete in solid floors.

44

Excavation and Timbering

Excavation Works

The excavation for foundations follows after the setting or laying out the building and

fixing of profiles. Excavations take various forms depending upon the type foundation to be laid.

Excavation

The term excavation means to hollow out. In building terms it means to remove earth to

form a cavity in the ground.

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, digging bars, forks and wheelbarrows.

Types of excavations

1. Over-site Excavation that involves the removal of topsoil up to 300mm deep.

2. Reduced Level Excavation which is carried out below the over-site level to form a level

surface on which to build and can consist of both cutting and filling operations. The

level to which the ground is removed is called the formation level.

3. Trench Excavations are narrow excavations that are primarily used for strip foundations

and buried services. Excavation can be carried out by either machine or hand.

Types of Trench Excavations

Battered faced

Vertical or straight faced

Battered Excavation Vertical/Straight Excavation

Reduced Level Excavation

This is necessary because very few sites are level in their natural state.

On small sites the process is similar as for Site clearance. Bulldozers are used for cut and fill

operation and a mechanical shovel plus Lorries are used for cut only operations.

Trench and Pit Excavations

On small sites the hand process can be used but if the depth of excavation exceeds

1.200m some method of removing spoil (soil) from the excavation will have to be employed. In

this event a trenching machine such as a Back actor could be employed.

Advantage: Advantage:

No temporary support is required to the

sides of the excavation

Minimum amount of soil is removed and

therefore minimum of backfill is required

Disadvantage: Disadvantage:

It incurs extra cost for over excavating and

extra backfilling

The sides of the excavation may require

some degree of temporary support

45

Types of Excavation Machines

46

Typical excavation machines include:

1. Bulldozers

2. Scrapers

3. Graders

4. Tractor Shovel

5. Skimmer

6. Face Shovel

7. Back actor

8. Dragline

9. Multi-Purpose Excavators

10. Trenchers

Mechanical - The bulk of major building projects is now performed. The principal machines are:

Dragline: A bucket dragged towards the machine, and it generally excavates below ground

level.

Face Shovel: This digs in deep faces above the level of its wheels or tracks.

Skimmer: This is used for shallow excavation up to 1.5 m deep and is particularly useful for

levelling and roadwork.

Drag Shovel or Back Actor: This digs below its own level and towards itself and is primarily

used for trench excavation.

Drag and Clamshell: This is for moving loose materials.

The Scraper: Operates like an earth plane and carries its scraping with it.

Bulldozer: This is used for, bulk excavation and grading.

Front End Loader and Back Hoe: This is for excavating and moving loose materials.

47

Timbering to Excavation

This is the term used to cover temporary supports to the sides of excavations and is

sometimes called planking and strutting. The sides of some excavations will need support to:

Protect the operatives while working in the excavation

Keep the excavation open by acting as a retaining wall to the sides of the trench.

The type and amount of timbering required will depend upon the depth and nature of the

subsoil, weather conditions, type of soil, and the duration of the operations.

Types

1. Timbering in firm soils

2. Timbering in dry loose soils

3. Timbering in loose wet soils

4. Timbering in hard soils

Safety

When excavating foundations and. drains in soil that is liable to fall away from the sides

of the trench, timbering should be used to prevent this (the soil from falling into the trench).

The builder must ensure all trenches are safely timbered or pile sheeted. Apart from the

death or injury, it will result in additional cost to the builder to re-excavate and new damaged

work in the trench should the sides collapse. Proper attention should be given to safety at all

times. The construction industry has a very high accident rate and every one in the industry must

be more safety conscious.

Timbering

Timbering is the temporary support used at sides of trenches to prevent caving in. The

support given to sides of the trench depends upon the depth of the trench and the soil conditions.

Weak soils will require more elaborate temporary support.

Terminology

Poling Boards: are vertical members that usually measure 175 mm x 31 mm x 1 m.

Walling Board: Horizontal members placed against the poling boards with cross section

measurement 150 mm x 75 mm. The length varies.

Struts: Horizontal supports placed across the trench to hold the other members in position. They

are spaced at centres between 1.5 m and 2 m along the length of the trench and are usually 100

mm x 100 mm in cross-section.

Wedges: Sometimes pairs of folding wedges are used between the walling boards and the struts

to take up slackness.

Types of Timbering

1. Open Boarding This is used for moderately firm ground such as sandy gravel, soft dry chalk, clayey, gravel.

2. Poles and struts

These are used for moderately firm ground, such as stiff clay, firm gravel and hard chalk. The

poling boards are spaced 1.829 m apart.

48

3. Close Boarding or Sheeting

This is used for unstable ground such as loose sand, wet soils and made up grounds.

Timbering in hard soils

49

Timbering in loose dry soils

50

Timbering in loose wet soils

Safety

Construction regulations state that:

1. Heavy loads or machinery likely to cause the collapse of the sides must not be moved close to

the excavation.

2. Open excavations must be fenced off to prevent persons falling into them.

3. Approaches to excavations must have warn1ng lights prominently d1splayed at night.

4. No vibration likely to bring about collapse of the sides must be caused close to the excavation

Curing

When concrete is poured it begins to set/cure and as time passes it becomes solid, and at

the same time increases in strength.

The chemical reaction which accompanies the setting of cement and hardening of

concrete is dependent on the retention of water is known as curing. Exposed concrete should

therefore be sprayed and covered with bubble plastic sheets or quilts of plastic with fibres or

straw or cement bags (sandbags), until it attains maximum strength (cures). To develop

maximum strength concrete requires the correct conditions and a certain minimum time,

depending on the temperature. Time ranges from 7 - 28 days for normal Portland cement.

Placing

All form work should be checked, cleaned and oiled before concrete is placed against it.

Concrete should not be permitted to fall freely more than one metre. When transported by a

barrow over rough ground segregation of the materials may occur as larger particles settle to the

51

bottom of the barrow. This will result in weakened concrete. To prevent or reduce this, use

pneumatic wheels to help cushion the shock.

Precautions

1. The area of concreting should be free from all debris.

2. The area of concreting should be washed.

3. The mixing bed should be as near as possible to concreting area.

4. The approach of the concreting should be free from all obstruction.

5. Oil the form work to allow ease of striking.

6. Do not allow concrete to fall freely more than one metre.

7. Use barrows with pneumatic wheels to reduce segregation of materials.

52

WALLS

Definition

•This term refers to a unit that is used to sub-divide or partition space.

•It is also considered to be a unit that encloses a space thus giving it a degree of protection from

the elements.

Categories of Walls

There are essentially two categories of walls namely:

• Load bearing walls and

• Non-load bearing walls.

Load bearing Walls

These are walls that are designed to transmit imposed and super-imposed loads in

addition to their own weight to a suitable foundation. They can either be external or internal

walls.

Non-load bearing Walls

These walls are designed to accommodate their own weight in addition to fixings placed

on them. Most often these are used internally.

Functional Requirements for Walls

A wall should be:

•Fire Resistant;

•sound insulated;

•weather resistant;

•thermally insulated;

•design to accommodate fixings such as doors and windows or openings, and

•designed to safely transmit all loads encountered to a suitable foundation.

Types of Walls:

•Rubble walls

•Brick walls

•Parapet walls

•Party walls

•Block walls

•Cavity walls

•Timber Framed walls

•Dwarf walls

•Concrete walls (In-situ and Prefabricated)

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Brick walls

The materials used in the manufacture of bricks is clay or it may be from sand or lime

and are available in a wide variety of strength, types, textures, colors, and special shaped bricks.

In the manufacturing process, the raw material (usually clay) is dug and then prepared

either by weathering or grinding before being mixed with water to the right plastic condition. It

is then formed into the required brick shape using a mould / form before being dried and fired in

a kiln.

•Bricks are generally manufactured to a length of 337.5mm, a width of 225mm and a height of

112.5 mm.

•However, the usual size of bricks for common use is 215 mm in length, width 102.5 mm and a

height of 65 mm where 10 mm of mortar joint thickness is added to 3 faces.

Bonding

This is an arrangement of bricks in a wall, column or pier laid to a set pattern to maintain

an adequate lap. The bond is set along the length of the wall working from each end to ensure

that no vertical joint is above another in consecutive courses.

Purpose of Bonding

Bonding is required:

•To ensure that maximum strength is obtain whilst the load to be transmitted through the

wall, column or pier is being distributed.

•To ensure that there is lateral stability and resistance to side thrusts.

•To create an aesthetic (acceptable) appearance.

Types of Bonds English Bond

This bond is formed by laying alternate courses of stretchers and headers. It is one of the

strongest forms of bonding pattern used.

English bond details

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Flemish Bond

This bond is formed by laying headers and stretchers consecutively in each course. It is

not as strong as English bond but is considered to be aesthetically superior.

Stretcher Bond

This bond consists of alternate courses of stretchers and is used extensively for block wall

construction.

Stretcher bond details

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Parapet Walls

This is a low wall projecting above the level of a roof, bridge or balcony forming a guard

or barrier at the edge. Parapets may be exposed to the elements on three faces namely front, rear

and top and will therefore need careful design and construction if they are to be durable and

reliable.

Party Walls

Party wall is an interior lot line used or adapted for joint service between two buildings.

Cavity Walls

These consist of an outer brick or block leaf or skin separated from an inner brick or

block leaf or skin by an air space called the cavity. These walls provide better thermal

insulation and weather resistant than block or brick wall. The two leaves of a cavity are

tied together with wall ties at not less than 900mm width and vertical heights of 450mm. (See

page 312 – 313)

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Cavity wall details

Timber Constructed Walls

Types: -

•Balloon Framed

•Platform Framed

Members:-

Foundation Footing, sill plate, sole plate, studs, Noggins, Top plate, wall plate, trimmer

stud, cripple stud, header, window sill.

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58

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Block walls

These are walling units exceeding in length, width or height the dimensions specified for

bricks. They are made from a mixture of cement, sand and marl/crushed stone to specific

proportions.

•The size of blocks varies depending on their use, but the standard length is given as length 400

mm, width from 75 mm up to 215 mm and a height of 200 mm.

•Blocks suitable for external solid walls are classified as load bearing and are required to have a

minimum average crushing strength of 2.8N/mm2.

Block walls

Characteristics

•Adequate strength

•Good insulation

•Low cost

•Good load bearing capabilities

Block walls

The core of blocks assumes more than 25% of its total area/volume. According to the

American Society for Testing and Materials (ASTM), blocks are graded based on compressive

strength and range from:

•600 psi – to be used above grade

•800 psi – used for all exterior walls

Definition of a Scaffold

These are three definitions of a scaffold:

1. A temporary platform either supported from below or suspended from above, on

which workers sit or stand when performing tasks at heights above the ground.

2. A raised wooden framework or platform.

3. A temporary structure of timber, boards, etc., for various purposes, as for

supporting workmen and materials in building.

Suspended Scaffolds

Supporting outrigger beams must be able to support 4 times the intended load. To keep a

scaffold from falling to the ground, it must be attached to the roof, tied to a secure anchorage, or

secured with counterweights. The suspension ropes and rigging must support at least 6 times the

intended load.

1. Counterweights must be attached to secure and strong places on a building so they

won‘t move.

2. Do not use bags of sand or gravel, masonry blocks, or roofing materials that can

flow or move.

3. Do not use gas-powered equipment or hoists. A hoist must have an automatic

brake for emergencies.

4. A 1-point or 2-point suspended scaffold must be tied or secured to prevent

swaying.

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Protection

There must be a 3½" high toe boards to prevent things falling off a scaffold. If things on

the scaffold are taller than 3½" (above the toe board), other systems, like debris nets, can be used

to catch falling tools or materials. If things can fall off a scaffold, people must be prevented from

walking under or near the scaffold.

Fall Protection

On most scaffolds, guard rails must be on all open sides and ends. On supported scaffolds

and some other scaffolds, guardrails or personal fall protection is enough. On most suspension

scaffolds, both are needed. Use a harness, not a body belt for personal fall protection.

You do not need a guard rail on the working side when the platform is less than 14" from the

work (18" for plastering and lathing). The open side of an outrigger must never be more than 3"

from the face of the building.

On supported scaffolds most of the time, the top rail must be 38" to 45" above the

platform. A top rail must be strong enough to hold 200 lb. (or 100 lb. on single-point and two-

point suspension scaffolds). A mid-rail must be about halfway between the platform and the top

rail; most mid-rails must be able to hold 150 pounds. If mesh, screens, or panels are used, a top

rail is needed (unless mesh was designed and installed to meet guardrail requirements). Scaffold

walkways must have no more than a 9.5" gap between planks and a guardrail. Don‘t let junk

collect on the scaffold. You can trip and fall.

Guidelines for checking a scaffold

If a scaffold is more than 2 feet above or below a level, there must be a way to get on or

off — such as a ladder, ramp, or personnel hoist. The way to get on or off must not be more than

14" away from the scaffold.

Put a standing scaffold on a firm foundation (with base plates attached to feet)for

instance, with one piece of wood under each pair of legs (across the shortest distance),

extending at least 1 foot past each leg.

Uprights must be vertical and braced to prevent swaying; platforms must be level

A scaffold that is more than 4 times higher than its base is wide must be tied to supports.

Scaffold setup and use

Scaffolds must be capable of supporting at least four times the maximum intended load.

Provide a ladder or equivalent safe access to all levels. The ―ladder-like‖ rungs on some brands

of commercial scaffolding are not to be used as a ladder. Note that a ladder leaned against

scaffolding on unlocked casters could cause the scaffolding assembly to roll away from the

ladder.

1. Ensure planks extend between 6 and 18 inches over their end supports unless they

are secured from movement, such as being attached with wire to the metal

supports.

2. Use a tag line when hoisting equipment onto a scaffold.

3. Do not allow tools, materials, and debris to accumulate and cause a falling hazard.

4. Wire or fibre rope used for scaffold suspension must be in good condition and

capable of supporting at least six times the intended load.

5. Install guardrails and toe boards at all open sides more than 3 m (10 feet) above

the ground or floor. Guardrails are not less than 5 x 10 cm (2 x 4 inches) cross

section, or the equivalent, and 0.9 to 1.1 m (36 to 42 inches) high. Diagonal or X-

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bracing can only be used as part of a guardrail system in some specific situations.

The minimum height for a toe board is 4 inches (10 cm).

6. Working on scaffolds is not only potentially hazardous for workers on the

platforms, but for people working below. Objects can fall on them despite the

presence of toe boards and the best intentions of the workers on the scaffold.

7. Restrict access and/or require hard hats for those below.

8. Ensure all wheel brakes are engaged except when movement is required.

Basic Safety

Most scaffold platforms and walkways must be 18" wide or more. If a work area is less

than 18" wide, guardrails and/or personal fall-arrest must be used.

Ten-foot planks must extend at least 6" past the end supports, but not more than 12"; no more

than 1" between planks or between planks and uprights.

Wood planks must be unpainted, so any cracks will show.

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Diagram of a scaffold

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What is Shoring

Shoring is a form of prop or support usually temporary that is used during the repair of

original construction of buildings and in excavations. Temporary support may be required, for

example, to relieve the load on a masonry wall while it is repaired or reinforced. The support

may be supplied by shoring the wall with the heavy timbers sloping upwards at about 65◦ to 75◦.

The top of the timber is so arranged that part of the wall load is transferred onto it while the

lower end of the timber is framed on to a base transfer the load to the ground with minimum

deformation. Wedges may be used to bring the shore snugly into contact with the wall. If the

wall is several stories high, vertical series of shores may be required. Shores are also used to

support the forms of cast-in-place concrete slabs, beams and girders in reinforced concrete

frames.

Another explanation of shoring is described below:

Shoring is often used to stabilize a building when it is to undergo structural modification

or repair. Commonly made of timbers measuring 12‖ (30.5 cm) by 12‖ shores are placed in an

inclined position bearing against the external wall of the building. The upper ends which are

sometimes capped with steel fit into niches cut in brick work and the lower ends rest on bases or

platforms. The application of wedges or steel jacks between the lower ends of the shores and the

platforms shift part of the weight of a building from its foundation to the shoring. Shores are

frequently used as supplemental support for buildings damaged by fire or by underpinning

failure. When employed horizontally e.g. when a building is removed from between two others

the shores consist of wood struts suitably braced and exerting pressure on wall plates in order to

distribute the thrust over a wide area. Shoring is also used widely in shipbuilding to support

hulls that are under construction.

Two Main Systems of Shoring

Dead Shores

This type is used to carry the dead load of the brick work etc. whenever an opening is to

be formed or when an existing opening needs to be widened.

Timbers of a square section are positioned above the line of a lintel or BRC. These are

therefore called needles because they pass through the wall. They are supported by timbers or

similar size called shores. The shores must be stood upon sole plates which in turn must stand on

firm ground preferably concrete. Shores should not normally exceed 1200 mm centre to centre

but the size of the opening and the amount of load to be supported above will dictate their size

and spacing. Cleats are nailed each side of the shore at sole plate level to prevent it becoming

dislodged while the other end metal dogs are used to secure the needle to the shore. Whatever

number of shores or needles are used they should be linked together by the sole plates and

bracing where necessary. The main consideration for the positioning of the shores is that they

should in no way interfere with placing the lintel or the beam into position. They should also

give the bricklayer room in which to work.

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Raking Shores

These are used for very different reasons from the dead shore. There may be occasions

when the two are used in conjunction with each other. Raking shores are designed to give

external support to a building which may have become in danger or collapse. They are rarely

used when the building is adjacent to a site where construction work is about to be undertaken

which could cause serious movement or vibration and the shoring is erected for precautionary

reasons. The system may consist of one or more rakers depending upon how many floors the

building possesses. A single raking shore consist of a wall piece of 225 x 75 mm secured flat

against the wall with metal wall hooks against which the shore is positioned. At the head of a

150 x 150 mm raking shore, a needle of 100 x 100 mm passes through the wall plate about half

way into the wall thickness. The angle of the shore should be about 60◦ and in no case should it

exceed 70◦. Particular attention must be paid to the position of the raking shores in relation to the

floors.

The foot of the shore is seated on to a sole plate which should be placed on a very firm

soil or weak concrete mix. An angle of 80◦ between the raking shore and the sole plate will

assist in allowing the raker to be eased into position without undue hammering.

A notch is formed in the foot of the raker to enable a nail or crow bar to be used for

easing the shore into position.

All shoring systems should be eased in the same way as arch centres before being totally

dismantled.

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FLOORS

By definition, the function of any floor is to provide a level surface that is capable of

supporting all the live and dead loads imposed.

Functional Requirements

The primary functions of floors are to:

• Provide a level surface with sufficient strength to support the imposed loads of people

and furniture.

• Exclude the passage of water and water vapour to the interior of the building.

• provide resistance to unacceptable heat loss through the floor

• Provide the correct type of surface to receive the chosen finish.

• be reasonably durable.

Categories of Floors

There are basically three types of floors widely used in the building industry, these are:

• Solid Ground Floors

• Suspended Timber Ground Floors

• Precast Concrete Floors

Solid Ground Floors

A domestic solid ground floor consists of three components:-

1. Hardcore

2. Damp Proof Membrane

3. Concrete Bed

Hardcore

This should be a suitable filling material to make up the topsoil removal and reduced

level excavations. It should have a top surface, which can be rolled out to ensure that cement

grout is not lost from the concrete. It may be necessary to blind the top surface with a layer of

sand or fine ash especially if the damp proof membrane is to be placed under the concrete bed.

Damp Proof Membrane

This is an impervious layer such as heavy-duty polythene sheeting that is used to prevent

moisture passing through the floor to the interior of the building. Other materials are,

• cold/hot poured bitumen,

• rubber solutions, and

• Asphalt or pitch mastic.

Concrete Bed

This is the component providing the solid level surface to which screeds and finishes can

be applied. The thicknesses that are generally specified are:

• Plain in-situ concrete (no reinforcement) 100-150mm thick

• Reinforced concrete, 150 mm minimum.

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Suspended Timber Ground Floor

This type of floor consists of timber boards or other suitable sheet material fixed to joists

spanning over sleeper walls. They are:

• Susceptible to dry rot (a fungus that attacks damp timber).

• Adequate ventilation under the floor coupled with damp proof courses at an appropriate

position will control or alleviate this problem.

• The use of airbricks is employed to allow for ventilation and should be spaced at 2 m

centre around the perimeter of the building.

Concrete Floors

The over site should not be less than 100mm thick although it is often 150 mm thick. The

mix of concrete should be at least 1:3:6 with a maximum size of coarse aggregates of 38 mm, but

a mix of 1:2:4 is to be preferred incorporating coarse aggregates with a maximum size of 19 mm.

the concrete mix of 50 kg of cement to not more than 0.11 m3 of fine aggregates and 0.16 m3 of

coarse aggregates. It should be noted that the edges of the slab are not to be built into the

surrounding walls to allow the two elements with their differing loads to move independently of

one another.

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Concrete floors

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Timber Floors

A timber floor finish laid directly on the bedded in a material which may also serve as a

damp proof membrane. Timber fillets laid in the concrete as a fixing for a floor finish should be

treated with an effective preservative unless they are above the DPM. The DPM must not be

lower than the highest level of surface of the outside ground and it must be continuous with, or

joined and sealed to, the DPM in any adjoining wall, floor pier, column or chimney.

Floor members

Joists-A steel or timber beam that supports a floor or roof

Sill- A ledge below a window or door

Sub floor- an underlying or rough unfinished material supporting a finished floor.

Header-A brick laid in a wall so that the smallest surface is visible

Bridging- are small metal pieces placed diagonally between floor joists.

Skirting- narrow boards around the margin of a floor sometimes called the baseboard.

Floor Members

Sleeper wall

• (Honeycomb built)

• Hardcore

• Over site concrete

• Wall plate

Floor framing members

Joists:

• Common, trimmed, trimming, and trimmer types

• Floor boarding

• Skirting

• Air bricks

Joist supports

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• Strutting

The honeycomb built sleeper walls

• These are usually built two or three courses high to allow good through ventilation.

• They are spaced at 2,000 mm centres which give an economical joist size.

• Wall plate is secured to the sleeper wall along with a DPC material. The joists are then

toe-nailed to it.

Floor Joists

The floor joists are pieces of timber that span between the wall plates and support the

floor boards. The size of the joists depends on the spacing of the sleeper walls. The table is a

guide to the appropriate lengths for joists that are spaced 400mm apart. Judging the length of the

joists correctly will reduce waste and time spent cutting the timber.

Span(mm) Joists size(mm) Joists length( mm)

1200 38 x 75 3800

1800 38 x 100 3100 or 4800

2000 50 x 100 4100

Trimmer, Trimming and Trimmed

A stair case will go through the first floor. Since you must form an opening, you will

need to cut into the joists. The joists around the opening are called (1) Trimmed Joist- they are

shortened by the opening, (2) Trimmer Joist- they support the trimmed joists, and Trimming

Joist- they support the end of the trimmer joists. This type of work is expensive and must be

done very carefully to minimize damage to the joists. The main principal is to join the end of the

trimmer joists firmly to the end of the trimming joists because the load is greatest at that point.

You can use a metal hanger or a house joint in the upper half to avoid cutting into the trimming

joist.

Joist Supports

The ends of the joists are supported or fixed to the load bearing walls by building them in or by

using special metal fixings called joist hangers among other methods, which are rarely used.

Strutting

• Timber is known to be hygroscopic, i.e. it is made up of cells, which will absorb moisture

readily.

• Significant changes in temperature and humidity may cause timber to expand, contract,

deform or twist.

• Shrinkage in timber joists will cause twisting to occur which can cause movements of the

ceiling below and surface cracks to the finishes applied.

• This problem can be overcome by inserting strutting between the joists if the span

exceeds 2,400 mm. The strutting is usually placed at mid-span.

• Typical arrangements of strutting are herringbone (metal or wood), inline solid and

staggered solid strutting.

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Joist Sizing (depth)

The sizing of joist can be determined by BC tables or

by formulas:

Formula 1

Rule of thumb:

Span in mm + 50 mm = depth of joist in mm.

24

It is assumed that the breadth joist is 50mm and is spaced at 400 c/c

Formula 2

Rule of thumb:

• BM = Wl/8 = fbd2/6

• Where;

• W = span x spacing of joist x floor loading kN/m2

• f = fibre stress of the material

• b = breadth (width) of joist (assumed to be 50mm)

• d2 = joist depth

• l = length of span

In-situ RC Suspended Floors

These are reinforced concrete slabs that incorporate beams spanning between columns.

The beams may span in one or two directions.

Slab variations are:

• One way spanning slab

• Two way spanning slab

• Two way spanning flat slab

• Other arrangements

Precast Concrete Floors

These floors are available in several basic formats and provide an alternative form of

floor construction to suspended timber floors and In-situ reinforced concrete suspended floors.

Advantages

The main advantages of precast concrete floors are:

• they eliminates the need for formwork inmost cases.

• curing time for concrete is eliminated therefore the floor is available at an earlier stage to

be used as a working platform.

• superior quality control of product is possible with factory-produced products.

Disadvantages

• Higher degree of site accuracy is required to ensure that the precast concrete floor units

can be accommodated without any alterations.

• Less flexible in design terms

• Formation of large openings to accommodate ducts, shafts and stairwells usually have to

be formed by casting an in-situ reinforced concrete floor strip around the opening

position.

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Types of Precast Floors

• PCC Beam and Pot Composite Floor

• PCC Channel Units

• PCC Plank and Pot Composite Floors

• Waffle Floors

Floor Finishes

These are finishes usually applied to a structural base but may form part of the floor

structure as in the case of floor boards. Most finishes are chosen to fulfil a particular function

based on several factors.

Types of Floor Finishes

• Quarry tiles

• Tongue and Groove Boarding

• Timber strip Flooring

• Wood Blocks

• Ceramic Tiles

• Floor Screed

• PVC Tiles

• Carpets and Carpet tiles

Factors of Floor Selection

• Appearance – chosen mainly for their aesthetic appeal or effect but should however have

reasonable wearing properties. Examples are carpets, carpet tiles and wood blocks.

• High resistance – chosen mainly for their wearing and impact resistance properties and

for high usage areas such as kitchens. Examples are quarry tiles and granolithic paving.

Hygiene – chosen to provide an impervious easy to clean surface with reasonable

aesthetic appeal. Examples are quarry tiles and polyvinyl chloride (PVC) sheets and tiles.

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Important Steps in Constructing a Timber Floor

Steps:

1. A timber joisted floor maybe covered with timber boards, or sheets or strips of

clipboard pr plywood. The majority of timber floor are finished or furnished with salt

wood board between 100mm and 150mm with a thickness of 25mm.

2. The boards are laid at right angles to the joists with two floor brads, of a width of the

brads being 40mm in length than thickness of the boards and the heads of the brads

well punched down below the top of the surface boards.

3. When constructing a timber floor the floor boards are normally joined together in

tongued and grooved joints, although in other expensive work, plain or square boards

can be used.

4. With a timber covered solid floor it is important to pressure impregnate the battens

and to apply a brush coat of preservative as a safe guard to prevent decay.

5. Where it is considered desirable to avoid punch holes for brads, boards may be secret

nailed and by using splay rebated, tongued and grooved joints, to help reduce the risk

of splitting the tongue when nailing. This method of nailing and jointing is really

suited for floor boarding.

6. Floor boards should preferably be rift sawn, when are cut as near radially from log as

near radially from log as practicable on conversation.

7. The edges of floor boards should be kept 13mm away from the surrounding walls to

allow movement and reduce the risk of damp penetration.

8. The gap is closed by skirting at the base of the wall or partition, which also masks the

gap between the button edge of the wall plaster and the floor, provides adequate

resistance to kicks.

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ROOFS

Definition:

A roof is a unit which covers the top of a building. It serves to protect the structure from

the weather and adds beauty to the design. Roofs are built with wood, concrete or steel

frames that are covered with decking and then a weather resistant roofing material.

Functional Requirements

• It should provide adequate weather exclusion

• It should be designed to provide the required degree of sound insulation

• It should be structurally sound so that maintenance can be done

• It should be providing light and ventilation

• It must be able to support its own weight, attached fixings, wind loads and imposed loads

• It should be thermally insulated

Factors Determining Roof Shape & Design

The shape chosen by architects and engineers depends upon factors such as:

• The size of the structure

• The design of the structure

• Climatic conditions

• Cost

• Appearance

Roof Classifications

• Roofs can be classified as either a Flat roof or a Pitched roof.

• A flat roof is one whose angle of slope lies between 0.0˚. to 10.0˚.

• A Pitched roof has a sloping angle over 10.0˚.but less than 70.0˚.

Types of Roofs

Lean-to Roof

This type is not often used on large spans, but more often found as a covering for a rear

or side extension to a larger building. The lean-to varies to suit requirements and the upper end

of the rafter is fixed to a wall piece which can be corbelled or bolted to the wall. The foot of the

rafter is normally birds-mouthed (notched) over a wall plate.

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Couple Roof

This is a double pitched roof of the simplest kind, consisting of common rafters birds-

mouthed over the wall plate and fixed to a ridge board at the apex. In general the birds-mouth

notching should not cut into the rafter any more than one third of the depth of the rafter. The

maximum span for this type of roof is 2.5 m.

Closed Couple Roof

This type is suitable for spans up to 4 m. It is stronger than the couple roof, having a

ceiling joist spanning the wall plates. This new Span member prevents the spread created by the

forces distributed to the wall plates by the rafters, thus making it suitable for the larger span.

Collar Roof

This type of roof is suitable for spans greater than 4 m, but up to a maximum of 5.5 m.

There is no specified position of the collar, but its effectiveness would be reduced considerably if

it was placed any more than half-way between the wall plates and ridge The most common

position used is one third of the height of the rise above the plates. If the collar is halved into the

common rafter with a dovetailed halving, as shown, the full strength of the tie will be achieved.

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Gable-end Roof

This is a double-pitched roof having two sloping surfaces and which terminates at the end

with a triangular section of block, wood, or brickwork.

Hipped-end Roof

This is a double-pitched roof where the roof slope is returned around the shorter sides of

the building to form a sloping triangular end.

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Eaves

The portion at the foot of the rafters which overhangs the wall face is called the eaves. It

serves various purposes which include:

1. protection of roof members

2. protection of walls

3. it offers good ventilation

4. it shows attractiveness

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Types of Ceilings

There are generally two types (suspended and close boarded) of ceilings, which serve the

following purposes:

1. tying together opposite walls and roofs

2. supporting upper floors

3. it offers good insulation

4. it offers aesthetics appearance

Advantages of using Roof Trusses

1. time

2. cost

3. strength

4. materials saving

5. weight reduction

6. quality control

7. ease of prefabrication

Types of roof coverings are:

1. Asphalt

2. Bituminous felt

3. Thatch

4. Plain tiles

5. Interlocking tiles

6. Corrugated sheet metal

7. Slates

8. Wood shingles

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Parts of a Roof

Technical Words for Parts of a Roof

Covering- is the external material that is laid over the roof structure to protect the inside of the

building. Coverings can be: asphalt; bituminous felt; thatch; plain tiles; interlocking tiles;

corrugated sheet metal

Eaves- the bottom end of the roof where it meets the wall

Fall – the slope required on flat roofs for water run-off

Fascia– a thin timber board that is fixed to the end of rafters or roof joists to support the gutters

Hip – the point where two inclined roof surfaces meet over an external angle

Jack rafter – a short rafter that spans the hip and eaves or valley and ridge

Pitch – the angle formed by the slope of the roof

Purling – A purling can be:

1. a horizontal timber that provides support to the rafters

2. a timber member spanning between roof trusses that supports roof sheets

Rafter – the timber member that spans from the eaves to the ridge in a pitched roof

Ridge Tile – a tile that caps the top of the roof

Ridge – a timber at the apex of the roof that takes the tops of the rafters

Soffit – the horizontal distance between the supports of structural members such as the rafters

Valley – the point where two inclined roof surfaces meet over an internal angle

Verge – the edge of a roof that meets a gable wall

Wall plate – is the timber member fixed to the top of a wall to secure a flat roof joist or rafter.

80

DOORS

A door is a movable barrier that separates internal and external spaces. It is usually attached

to a frame on one side by hinges. As it is, it performs various functions which include:

1. Protection

2. Security

3. Privacy

4. light

5. access/exit

6. ventilation

Types of Doors

Panel Doors

These can be described as one-panel, two-panel three panels etc. up to as many as twelve

panels. Panel doors consist of panels, stiles, top, bottom and middle rails and sometimes

muntins, which are vertical intermediate pieces tenoned to the top, bottom or middle rails.

Panels to doors can be glass, plain plywood, and plain solid timber or raised solid timber.

These doors are suitable for both internal and external use.

The Parts of a Panelled Door

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Flush Doors

Flush doors are very popular, on the account of their plainness, low cost and ease of

construction. A flush door consists of a core of either laminated solid timber or skeleton

framework with a facing of plywood. The strongest type of flush door is the solid core, which is

constructed using strips of timber that are laminated to form a solid board, with a facing of

plywood on both sides.

Ledged, Braced and Batten Doors

This is a very simple door for internal or external use; which is cheap to make.

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Framed, Braced and Batten Doors

This door is stronger than the ledged, braced and battens because the battens are set

inside a timber frame. The framed, braced and battened door consists of these pieces:

- battens that form the surface of the door

- a frame with a head rail, bottom rail and two stiles

- a ledge

- braces

83

Door Ironmongery

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Door Dimensions

Doors for domestic buildings are usually about 2 metres high. Their width varies.

Type of Doors Thickness (mm) Width (mm)

External 40-50 760-900

Internal 40 680-760

Fire-resistant 44 760-900

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WINDOWS

Functions of Windows

Windows on a building provide natural light and ventilation to the interior while excluding

rain and insects. Windows are usually made of steel or timber, but other materials such as

plastics or aluminium are also popular. As such windows serve various functions which are:

(1) Provides lighting and ventilation

(2) Sound reduction

(3) Appearance

(4) External viewing

(5) Emergency exit

(6) Security

Building Regulations for Windows

Windows are usually put together in combinations of openings and fixed lights to comply

with the regulations for health and hygiene in habitable rooms. The standard requirements in

most buildings regulations are usually:

(1) The minimum area of window in a habitable room should be 10 per cent of the floor area.

(2) The minimum opening area of the window in a habitable room should be 5 per cent of the

floor area

Glazing

The glazing is the glass part of the window. Glass is essential to let in daylight, but to

exclude wind and rain.

The thickness of the pane depends on its height, width and the amount of likely wind

pressure. These types of glass are commonly used in small buildings:

1. Clear Glass, which is about 3 to 4 mm thick;

2. Obscure Glass, which is used in private areas such as toilets and bathrooms. It is usually

4mm thick and comes in a variety of patterns;

3. Special Glass, which is used in internal or external doors that require stronger safety glass

There are two main types of special glass:

1. Wired Glass, which can be clear or obscure. It is about 6 mm thick and is reinforced with

wire;

2. Toughened Glass, which is manufactured to a specific size and cannot be cut. When this

glass breaks it shatters into harmless pieces. Car windshields are made from toughened

glass.

Technical Terms for parts of a window and frame:

Bottom rail – the bottom member of a sash or light

Head – the top piece of a window, which is fixed to the underside of the masonry

Casement – a side-hung opening window

Sill – the bottom piece of a window, which is fixed to the bottom of the opening

Jamb – the vertical sidepiece fixed to the surface of the window opening

Mullin – a fixed vertical piece in the window framework, which separates the fixed and moving

parts

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Opening light – another word for sash

Sash – the whole moving part of a window including the glass

Stile – the side member of the sash

Top rail – the top member of the sash

Transom – the fixed horizontal piece that separates the fixed and moving parts of the window

Ventilator – a small sash, which is often top-hung to provide secure ventilation

Types of Windows

Awning –An awning window unit has a frame with one or more sash which swings outward at

the bottom. This window can keep rain out even if this is open. Awning windows usually come

with weather stripping and storm sash and screens.

Hopper – This type of window has a sash that swings inward at the top. This window can keep

the rain out even if they are open.

Sash – Sash windows are those in which the sashes slide up and down and they are normally

consist of two sashes, placed one above. Where both sashes open they are termed as double-hung

sash windows.

Casement – With wood casement windows, a solid frame is fixed to the edges of the opening

and this receives the glazed casements which may be side hung, top hung or bottom hung. Small

top or bottom hung casements are used for controlled ventilation, whereas the larger side hung

casement can be opened for greater ventilation in warmer weather. Side hung casement can

create a safety hazard with young children and where above ground level is very difficult to

clean.

Figure Showing a Typical Wood Casement Window Assembly

Pivot – These are windows that are hung at the top and side by hinges, and the sashes are pivoted

in their frames.

Louvre - This is individual pieces of glass held in clips and opened by a lever arm, which locks

the louvre in position.

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1. side-hung casement window

2. side light

3. top light

4. sliding folding window

5. top-hung casement window, awning window

6. bottom-hung casement window, hopper window

7. horizontal pivot window

8. vertical pivot window

9. top-hung sliding window

10. vertical sliding sash window

11. horizontal sliding window

12. louvered window

13. centre hinge, centre pivot hinge

88

WINDOW IRONMONGERY

89

STAIRS

Buildings have stairs so that people can:

(1) Gain access from one floor to another

(2) A way to make emergency escape

(3) Decorative purposes

(4) Means of transportation of goods from one floor to another

(5) Join two or more floors together

Some common terms associated with Stairs

Rise - The vertical distance between the top of adjacent treads

Tread - The horizontal surface of a step where you place your feet

Stringer/String - A structural member that supports the tread and riser

Going/Run - The horizontal distance between the nosing of the adjacent treads

Step - A combination of treads and risers

Flight - A series of steps between floors

Handrail - A rail fixed in a position to give assistance to the user of the stair, which is

either fixed a wall or supported by a Balustrade

Balustrade - The protection erected on the other edge of the staircase to prevent anything falling

off the edge

Baluster - Rails between the hand rail and the string

Stair well/case - The opening in which stairs to be constructed

Newel- The post at the end of a flight of stairs to which the stringers and handrail are fixed,

usually 100 x 100m

Building Regulations regarding Stairs

(1) Maximum pitch must be 42‖

(2) Going of any step must not be less than 220mm

(3) The rise of any step must not be more than 220mm

(4) For any flier the sum of going plus twice the rise must not exceed 700mm or less than

500mm (2 riser + going = 500mm

(5) Headroom must not be less than 2m above the pitch line vertically

(6) Any stairway less than 1m wide should have one handrail or two handrails more than 1m

wide

(7) Handrails should not be less than 840mm vertical height on the pitch line and not less

than 900mm above the landing

Given a stair to construct, distance from the finished lower to the finished upper floor is the total

rise.

The ceiling height is 3m and floor thickness is 150mm.

The total rise is the sum of ceiling height and floor thickness which is 3.0m + 150mm = 3.150m

assuming that the total going is 3.60m.

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Calculate the tread and riser:

Total rise

Rise = Number of risers (an ideal height for a riser is 187mm) an formula used is

(2 risers + going) = 550mm – 700mm

Divide the total rise 3.150m by 187mm = 16.3 risers or 17 risers

Each rise = 3.150 = 185mm

17

Total going

Going = Number of treads (number of treads is always one less than the number of risers)

Going =3.60m = 225mm

16

Therefore – 2 risers + Going = 550mm – 700mm

(2 x 185mm) + 225mm =

595mm = 550mm – 700mm

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FINISHES

Rendering

External rendering is the process of applying a cement and sand plaster coat to the

outside walls of a building.

You render to:

(1) to improve the appearance of concrete block walls;

(2) provide a waterproof finish to porous blocks

(3) Provide a base for a colour finish.

Smooth render is a cement and lime mixed with sand and a 1:2:9 mixture. It is put on as a

finishing coat and trowelled to a smooth finish. If an undercoat is needed, then the proportions

should be reduced to 1:1:5. This is the least satisfactory finish because the trowelling can bring

too much cement to the surface, which causes cracks.

Roughcast render is a top coat of cement, lime and sand in a 1:2:9 mix over a 1:3 cement and

sand backing coat. While the top coat is soft, you throw 6-13mm cement-coated aggregate into it.

Scraped render is a 1:1:6 or 1:2:9 mix of cement, lime and sand. You scrape the top 2mm off

with a saw blade just before it hardens to remove the smooth skin.

Pebbledash render is a final coat in a 1:1:6 cement, lime and sand render with 6-12 mm pebbles

lightly pressed into it so that the aggregate is exposed.

Tyrolean (popcorn) render is produced by a machine that throws a 1:3 cement and mixture onto

the wall for a deeply textured finish. The cement can be coloured to produce a permanent

coloured finish. The background can be rendered or the Tyrolean render can be applied directly

to a raw wall and built up in layers.

Plastering

The term plastering means the application of a smooth coat of material to walls and

ceilings. The purpose of plastering is to provide a joint less, hygienic, and easily decorated

smooth finish to walls. Plaster is mixed with water to make a plastic mixture, which can be

spread directly on a surface in a thin 10mm layer. The surface absorbs the water in the mix by a

process called suction. The suction process stiffens the plaster rapidly so that you can level it

while it hardens and sets. When the plaster dries it leaves a hard, smooth finish for decoration.

The type of concrete that you might plaster would be the soffit of a floor slab. The concrete may

be quite smooth from the concrete was poured. To prepare concrete, you need to wash off all

traces of oil and hack the surface to provide enough key for the plaster. You may apply one, two

or three coats of plaster to achieve a smooth finish. Generally, you need to apply two coats

unless you using plasterboards, which need only one. Three coats are only used if the surface is

extremely uneven. The first coat in a three-coat finish, called a screed coat, is applied to level the

surface and to ensure that the plaster is the correct thickness.

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How to plaster a wall

(1) put mounds of cement and sand mortar across the wall in columns of three about

1200mm apart, smooth the mounds to a thickness of 10mm and leave them to hard.

(2) Apply 75mm vertical strips of plaster over the mounds and leave them to set

(3) Mix the plaster by hand or with a small mixer.

(4) Apply a rough plaster coat to the wall between the screeds by putting it on with an

upward sweeping movement.

(5) Move the screed board from the bottom to the top of the wall in a sawing motion to

smooth and level the plaster

(6) Scratch the first coat before it sets to provide a key for the second coat and leave to dry.

(7) Apply a finish coat of 2mm neat plaster with a steel float to produce a thick, smooth

finish.

Types of paints

The main types of paint are: gloss, undercoats for gloss, primers and water-thinned.

Gloss paints are based on resins produced in laboratories which have improved the quality of

gloss paints the two main types of gloss paints are paints thinned with white spirit and paints

thinned with water. White spirit is turpentine which is used to dilute gloss paint and to clean

brushes and paints spills. The gloss paints that are thinned with water are easier to use and clean

up after.

Undercoats for gloss paints are modified gloss paints that dry with flat finishes. This makes it

easier to rub them down and improves the adhesion of the gloss coat. Undercoat also fill in the

colour over the primer and consolidate the final colour.

Primers are applied to seal unpainted metal and wood surfaces, typical wood primers are: pink

primer, aluminium wood primer, acrylic primers.

Metal primers are calcium plumbate, zinc chromate.

Water-based (acrylic) these are less durable than gloss paints, but they are also easier to apply.

Because they don‘t seal surfaces, you can use these paints on new plaster. Water-thinned paints

have the primer, undercoat and finish in the same container. Two types of water-thinned paints

are: lime washes and emulsions.

Varnish is a transparent solution that solidifies into a protective coating. Opaque and coloured

varnishes are called lacquers.

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Properties of Paints and Varnishes

Paint

The properties of paint are: a pigment, a binder and a solvent or thinner to make the

mixture suitable for application. Paint pigment is a fine powder that either strongly scatters light,

to yield a white effect, or absorbs certain wavelengths of light, producing a coloured effect.

After application, the paint undergoes changes which convert it from a fluid to a tough film

which binds the pigment. The nature of these changes varies with different types of paint. Some

such as size- bound distemper and chlorinated rubber paint lose the thinner by evaporation. With

most paints containing drying oils, part of the change on drying results reaction of the oil with

oxygen from the air. In emulsion paints and oil-bound distempers, the binding material is

emulsified or dispersed as fine globules in an aqueous liquid. After application the water

evaporates and the globules coalesce to form a tough, water resistant film.

Varnishes

Varnishes are transparent solutions produced by heating a drying oil, resin, drier, and

solvent together. If applied as a thin film, varnish gives a hard transparent coating upon

evaporation, oxidation, and polymerization of the solvent. The numerous variations in

composition and preparation of varnish make its classification difficult. The so-called spirit

varnish, for example, is a resin dissolved in a volatile solvent that contains no drying oil, and

asphalt varnish is a solution of asphalt and a solvent that gives opaque, black coatings. Opaque

and coloured varnishes are called lacquers.

Stains

A stain is a chemical dye or pigment used to color glass, paper, textiles, or wood. The

staining substance, which uses alcohol, oil, or water as a vehicle, is transparent and thinner than

paint or coating, and it penetrates into the grain of material being dyed.

Methods of Application

Paints

Paints are applied to:

- Masonry by roller, air brush, hand brush or spray.

- Metal by roller, air brush, hand brush or spray.

- Wood surfaces by air brush, hand brush, roller or spray.

Varnishes

Varnishes are applied to:

- Wood surfaces by roller, air brush, spray or by hand brush.

Stains

Stains are applied to:

- Wood surfaces by airbrush, hand brush, spray or roller.

Brushes and rollers are used in many different sizes according to convenience.

The Purpose of Solvents

Solvents

The purpose of solvents is to dry paint when applied by causing it to evaporate, oxidize

or polymerize.

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Laying tiles on concrete sub-floors

Tiles are made from a variety of materials and laid on sub-floor in individual units to

form a complete covering. They are laid on an adhesive or mortar bed, depending on the tile

material. Some tiles are having wide joints, which are filled separately, while others are filled so

tightly that no joint filling is needed.

PVC Tiles

PVC tiles have precise measurements (300 300 3 mm). They must be laid on a

perfectly smooth screed because they are so thin and fixed with adhesive. However, they can be

fitted so closely that they do not have a gap in the joints.

PVC tiles are usually:

Resistant to grease and oil;

Waterproof;

Durable.

Although they come in a wide range of colours and texture, PVC tiles are one of the cheapest

floor finishes you can buy and lay. They are maintained by applying a surface coating of wax

and then washing with soapy water.

Quarry and Ceramic Tiles

Ceramic tiles are clay tiles with a hard semi-glazed finish. They are usually measure

about 150 150 mm or 100 100 mm and are 15-20 mm thick. Since they are fired in a kiln they

are not shaped as precisely as PVC tiles, so they have a 3-mm joint between the tiles.

Quarry are made of natural stone and cut from the slabs in quarries. These tiles are

bedded in mortar so a levelling screed is not necessary. The level of the finish floor is determined

by battens, which are the thickness of the tile, fixed temporarily to the floor and levelled. The

bedding should be a 1:10 mix of cement and sand mortar. You spread the mortar on the concrete

and the bed the tiles level to the battens. The joints should be grouted with 1:1 sanded grout.

Finishes on Timber Floor

It is usually not practical to lay any cement-based finishes on timber floor. Because

timber moves and flexes, it is liable to cause crack in the floor finish. The added weight of a

cement-based finish would also mean that the floor construction would have a heavier and

stronger.

The finishes that can be laid on timber floors are:

1. PVC tiles, which can be laid on the flooring as long as the boards are flush at the joints. It is

safer to lay a 3-mm hardboard cover over standard 100-mm strip flooring to avoid the joints

showing through;

2. Carpet, which can be from a wide range of qualities and styles. And underlay will protect the

carpet and extend its lifespan. You can lay carpet loosely as squares and rectangles, fit it from

wall to wall in seamless areas or lay carpet tiles on adhesive back.

Types of Tiles

Square tiles are the most popular. They come in three varieties to suit the expose ends of

the tile runs. The basic tile, which is glazed on the surface only, has unglazed edges. The surface

of the basic tile can be:

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1. Slightly rounded near the edges. This is a cushion-edges tile;

2. rounded on one edge;

3. Rounded on the two edges.

Tiling Techniques

To produce good tiling you need to know how to:

1. level;

2. cut tiles;

3. set out and measure;

4. Grout joints.

Glass Blocks

Glass blocks are very thick blocks of glass made with metal reinforces between them.

Glass blocks have been in use since the early 1900- they timeless projects that can be used in any

type of architecture.

Glass blocks are usually used as walls, windows, or floors. Imaginative new design

elements make for new more exciting looks for building projects. They also require very little

maintenance.

Glass blocks are one of the sound insulating materials. Compare with windows made from other

materials, glass block windows have a much better heat insulation making it somewhat fire

proof. The heat insulation plays a role in avoiding frosting in the winter

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RELATED SERVICES

The Principles of Plumbing Pipes

The principles of plumbing pipes are:

Types

Size

Materials

Methods of Joining

Fittings

Types

Drainpipes can be made from a variety of materials. Your choice of drain pipe will

depend on availability, price and suitability for the purpose. This list describes some of the most

common materials for drainpipes:

1. Vitrified Clay, which is clay that was fired at a very high temperature to make it

waterproof;

2. Cast Iron, which is a very hard metal alloy. This material is quite expensive and is

normally only used for commercial buildings.

3. Concrete, which is cast using the methods of production used for concrete.

4. Pitch Fibre, which is made from pitch fibres or waste fibres and bitumen or pitch;

5. Plastic, commonly known as polyvinyl chloride (PVC). This is a popular material

because it comes in long lengths, is light and makes joints easily.

Size

Common sizes are 50 mm for wash basins and WC flushing, cisterns and 50 mm for

multiple sinks and baths. A minimum 100 mm drain is usually adequate for a domestic plot.

About 20 small houses can be connected to a 100 mm drain because only one or two will

discharge water at the same time. If required, then a larger pipe one with a 150mm diameter is

available.

Materials

UPVC is the most popular material because it does not need decoration, it is light weight

and easy to fix. It does not rot or corrode. However this material is easily damaged and is not

suitable for areas where it could be hit by moving vehicles. Fibre cement is a durable and heavier

material than the plastic and requires more joints and supports.

A variety of materials is available for water supply pipes, of which probably the most

popular is light gauge copper tube, largely on account of its durability, flexibility, smooth bore,

neat appearance and ease of jointing. Polythene pipes are rather soft, not completely resistant to

ground gases, need ample support and cannot be used for grounding electrical instillations.

Polythene pipes are flexible and their smooth bore speed water flow and prevents the formation

of scale. Lead pipes are now little used on the account of their high cost, weight and suitability

with soft or acid water and their use in new dwellings is not permitted. Mild steel pipes are

relatively strong and inexpensive, and are made in three categories- light, medium and heavy.

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Methods of Jointing and Fittings

Methods of joining chosen depend on whether you are using:

Rigid Pipes with Rigid Joints

Rigid pipes made from clay, concrete or cast iron need rigid joints with sockets that are

wide enough to insert pipes with straight ends, called spigots. There should be enough space

around the jointing material.

Rigid pipes with Flexible Joints

Recent developments in pipe technology have made it possible to use rigid pipes with

joints that allow some flexibility. This is useful because rigid joints may crack with slight

movement. Two types of flexible joints are:

1. Spigot and socket combinations

2. Polypropylene sleeves.

These combinations can be used to make to make flexible joints for concrete pipes.

Flexible pipes with Flexible Joints

Flexible pipes distort under loads. This distortion should be limited to 5 per cent of the

pipes diameter to maintain the flow of water. Similarly, the flexibility of the joint should only

take up slight movement so that the pipe maintains the correct falls. You can join pitch fibre

pipes with polypropylene sleeves with gaskets or by tapering the ends of the pipe and driving

them into collars. PVC pipes are made with socket and spigot ends. They can be joined by using

a solvent weld the pipes together so that one pipe sits slightly inside the other or by inserting

rubber rings into the grooves of the sockets and spigots.

- The most common form of joining mild steel pipes is screwed and socket.

- In plastics compression is probably the best method of jointing.

- Soldered joints are normally used in lead pipes.

In the house the main sanitary fittings are:

- WC;

- Bath;

- Sink;

- Basin:

- Shower.

They should be made of materials that are easy to clean, durable and water proof.

The principles of roof drainage and disposal are:

Pitch/Slope

Gutters

Down pipes

Soak away

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Pitch/Slope

The pitch or slope is the angle of the slope of the roof measured from the horizontal. A

steeper pitch needs more roof-covering material, which increases the weight to be supported. The

surface is affected by wind so therefore the roof needs to be strong enough to allow for the

factors.

Gutters

A gutter is a channel fixed to the long edge of a roof. The bracket on fixings on the fascia

should be at 900mm intervals. A gutter will have an outlet which is a spout that points down to

connect with a rain water pipe. In most domestic buildings, one outlet is usually enough to take

the rainwater during normal wet weather. The distribution of water along the length of the gutter

pushes it naturally towards the outlet. Any residue of water usually evaporates.

Gutters are available in various lengths and are made from various materials such as:

- Cast Iron

- Asbestos and cement

- PVC-U

- Pressed steel galvanize

- Aluminium

- Wrought copper and wrought zinc

Down pipes

Down pipes convey rain water from roof gutters to underground drains, often through a

back entry water gully at ground level. When used with projecting eaves they generally require a

swan-neck consisting of a fitting with two bends to negotiate the soffit. Flat roofs parapet gutters

may discharge into may discharge into rain water heads at the top of down pipes.

There are various materials which down pipes are made form such as:

- Cast iron spigot and socket down pipes

- Asbestos cement spigot and socket down pipes

- PVC-U down pipes

- Pressed steel galvanized light gauge down pipes

- Aluminium down pipes

- Wrought copper and wrought zinc down pipes.

Wire balloons of galvanized steel, aluminium or copper should be inserted in gutter outlets to

prevent blockages occurring down pipes.

Soak-away (soak pit)

A soak-away is a rubber-filled pit in the ground which absorbs water quickly. Test for the

right type of ground are usually done. You can calculate the size of soak-away needed by

multiplying the size of the area to be drained, by the average annual rainfall in metres and

dividing by 3.

Example

The area to be drained= 200mm2

The average rainfall per hour= 75mm

200 x 0.075/3 = 5 m3

The Combine System of Drainage

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This is a system whereby foul water from sanitary appliances and surface water from

roofs and paved areas discharge through a single drain to the same combined sewer. This

simplifies and cheapens the house drainage system, ensuring that the drains are well flushed in

time of storm so that the house drain cannot be connected to the wrong sewer. On the other hand

silting may occur in large pipes and it may entail storm overflows on sewers and high cost of

pumping and sewage treatment. Building regulations describe foul water as waste water which

comprises or includes;

The Separate System of Drainage

A separate drainage system is one in which foul wastes pass through one set of drains to a

foul sewer, whereas surface water is conveyed to a separate surface sewer or soak- away. This

arrangement reduces pumping and sewage treatment costs to the main drainage authority but

result in additional expense in the house drainage system, eliminates the flushing action of the

surface water in foul drains and permits the possibility of an incorrect connection.

The Principles of Drain Runs

Methods of sewage disposal

Building regulations requires any cesspool, septic tank or settlement tank to be:

a) of adequate capacity and so constructed that it is impermeable to liquids;

b) adequately ventilated; and

c) so sited and constructed that-

it is not prejudicial to the health of any person,

it will not contaminate any underground water or water supply, and

There are adequate means of access for emptying.

Cesspool

A cesspool is an underground chamber constructed for the reception and storage of foul

water from the building until it is emptied. It is a requirement that cesspools should be

constructed so as to prevent leakage of its contents and ingress of subsoil water. Adequate

ventilation, is sited so as not to prejudicial to health nor to contaminate water supplies, as well as

permit satisfactory access from emptying and have a minimum capacity below the level of invert

of 1800 litres (18m3). Cesspools if they are to be emptied using a tanker, should be sited within a

30m of a vehicle access and at such levels that they can be emptied and cleaned without hazard

to the building occupants or the contents being taken through a dwelling or place of work. When

sitting a cesspool attention should be paid to the slope of the ground, direction of the prevailing

wind, access for emptying and possibility of future connection to a sewer. It should be sited a

minimum of 15m away from any inhabited building. Cesspools should only be used when no

alternatives are available.

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Septic Tank

A septic tank is a brick- lined tank set into the ground, which receives the discharges

from a building. After treatment from natural processes, the discharge leaves the septic tank and

filters into the soil. If a house does not have a pipe system for removing waste, a septic tank can

be installed. Depending on the size, septic tanks can serve one plot or a small community. The

smallest septic tank should have a capacity of at least 3000 litres or 3m3. A two metre deep tank

which is 2 x 2 x 1m has an internal volume of 4m3or 4000 litres. A septic tank works by using

anaerobic bacteria, which do not need oxygen, to break down solid sewage into liquid and

sludge. Raw sewage enters one end and emerges as liquid effluent at the other end. A drain

takes the liquid to a soak-away where it filters into the soil. Inside the tank, gases cause the

solids to liquefy and break up. After the solid settles as sludge, then anaerobic bacteria breaks it

down until it forms scum on the surface, which at six month intervals should be pumped out.

The residue in the tank starts the bacterial action again.

The location of a septic tank depends on these principles:

Access for pumping it out; it must be convenient.

It should be at least 3 m from a building.

It should be down wind

The effluent should not discharge into water supplies or streams.

Soak away (soak pit)

A soak-away is a rubble filled pit in the ground which absorbs water quickly and if

rainwater flowed off the roof of a building in an uncontrolled way, then it could flood the

building and inconvenience the occupants. Water can also flow off of shallow eaves and find its

way into a building through walls and windows. For these reasons, it is better to collect water at

eaves in a gutter and direct it down to the ground in a rain water pipe. The rainwater can then

drain away underground and discharge into the soak away.

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SOAK AWAY

Absorption Pits- An absorption pit is a critical component of the system and refers to the area in

which the water from the septic tank flows through.

A chemical Chamber- This chamber function is to detoxify the sludge sediment and make it

environmentally safe. This sludge may be neutralized for safe land application, and the metals

can be recovered from the water using existing conventional dewatering techniques separating

the detoxified, acidic sludge and the acidic, heavy metal containing water.

Disposal Fields- It is from here that the sewage after been collected to the septic tank the liquid

portion of it is then dispersed naturally into the surrounding area via underground.

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THE BUILDING TEAM AND BUILDING TRADES

The Building Team

Building is essentially a team effort in which member has an important role to play.

Building Owner/the Client; is the person who commissions the work and directly or indirectly

employs everybody.

Architect; is someone who is employed by the owner to draw and design the building.

Clerks of works; Employed on large contracts as the architect onsite representative. He can

only offer advice. He makes sure that the contractor builds the building correctly and safely.

Quantity Surveyor; prepares a bill of quantity for building projects so the contractor can

accurately price the work.

Engineers; make sure that the buildings are structurally stable. The engineer calculates the

weight of the construction materials, the weight of the people and equipment who will occupy

the house and the maximum pressure on the building.

Site Agent; is the contractor‘s representative on large contracts. He also manages the site on a

day to day basis.

Contractor; employed by the building owner to build the building according to the design

drawings, specifications and quantities.

Building Owner

Contractor Clerk Of works Quantity Survey Engineer

Site Agent

Architect

Contracts Mang. Surveyor

General Foreman

Trades Foreman

Operatives

Estimator Buyer

Administrator

Costing

Accounts

Office Staff

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Surveyor; lays out the shape of the building on the ground before construction starts. The

surveyor also checks the ground level.

Estimator- works out the cost of construction, the proposed buildings shown on the drawing.

Buyer; order materials, obtains quotations for the supply pf materials and services.

Accountant; prepares and submits account to clients and make payments to supplies and sub-

contractors.

Administrator - organises the general clerical duties of the contractor‘s office for the payments

of wages, insurances and all necessary correspondence.

Contracts manager - has overall responsibility for the site operations.

General foreman; employed on small contracts. This individual should have extensive

knowledge of all aspects of building construction. He should know how to organise the

materials, workers and schedules.

Trades foreman; is experienced at specific trades such as brick work, carpentry or plumbing.

They organize and control their workers in their own trade.

Operatives; the main work force onsite, including tradesmen, apprentices and labourers.

Various Building Trades

Carpentry (Carpenter) – installs doors, construct roofs, and construct formwork.

Electrical Wiring (Electrician) – installs electrical fixtures, carries out wiring work.

Masonry/Tiling (Mason/Tradesman) – works with concrete and mortar. Lays tiles, builds stone

walls.

Painting (Painter) – responsible for finishing the building by applying paint

- Finish Joinery Fitments with various types of finishes. eg. Varnish, stains etc.

Plumbing (Plumber) – lays pipes, installs taps, installs toilet bowls etc.

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HISTORY OF BUILDINGS

Factors Influencing Building Designs

History – History of site: flood prone, landslide, built up and previous use

Material – choice and availability of material

Culture – would have an influence on the shape and style of the structure

Climate – wet, cold, windy would determine where windows or balcony are placed in a building

Cost – would determine affordability

Influence of Other Culture on Local Building Styles

British

- Bricks

- Arches

- MDF

- Steep Roof

- Dormers

- Casement Windows

- Architraves

American

- High rise building

- Dry wall

- Steel frame building

- Split-level building with separate roofs for each

- Panel construction