UNESCO-NIGERIA TECHNICAL &

VOCATIONAL EDUCATION REVITALISATION

PROJECT-PHASE II

YEAR I- SEMESTER I

THEORY Version 1: December 2008

NATIONAL DIPLOMA IN

CIVIL ENGINEERING

TECHNOLOGY

CIVIL ENGINEERING CONSTRUCTION I

COURSE CODE: CEC105

TABLE OF CONTENTS

Week 1 Building Component

Week 2 Site Preparation

Week 3 Method of Setting Out

Wee 4 Excavations

Week 5 Foundations

Week 6 Damp Proofing, Sub-Structural Works, Rising and seepage of ground

and underground water

Week 7 Floors

Week 8 Walls

Week 9 Brick Bonding

Week 10 Partition Walling

Week 11 Stairs/Staircase

Week 12 Roofs

Week 13 Flat Roofs

Week 14 Slates

Week 15 Suspended Ceilings System

WEEK 1

COURSE: CIVIL ENGINEERING CONSTRUCTION 1

1.0 BUILDING COMPONENTS

1.1 Explain the term Building Component

To understand and to be able to explain the term building component.

It will be necessary to take cognizance of the following definitions:

BUILD – This is to make by putting elements, parts or materials

together to form something.

CONSTRUCTION – This is the putting together and assembling of

elements and material in other to erect or build a structure.

BUILDING – This is the act of constructing houses.

COMPONENT – This is a word that describes an element, part or

materials that contribute to the formation of a structure.

From the above definitions, it could be stated that Building

Components are structural elements or materials that can be

assembled, by the following approved construction procedures and

rules, to make up or form a building. The components to be used

depend largely on the purpose of the building (i.e. residential, factory

or recreations, etc.). high-rise building. Examples of building

components are foundation floor, wall ceiling, roof, doors, windows,

etc.

A building is so called because of the assemblage of most of these

components. Absence of some of these component parts depending

on the purpose of the building, will render it incomplete, structurally

waste and inhabitable. E.g. imagine a building without a foundation,

walls or roof, will be as good as piece of land with first farmers a tree

without root, man with

1.2 Enumerate the building components, e.g. foundation, floor, wall,

ceiling, roof, fenestration, doors, windows, stairs, etc.

Foundation Columns

Floor Slabs

Wall

Ceiling

Roof

Fenestration

Doors

Windows

Stairs

Chimney

1.3 Identify the different functional requirements of building

components

The component parts or materials that make up or forms a building

are normally designed to perform some specific function or for a

specific purpose in the building. Part from the beautification of the

structure, building components should perform some certain

functional requirements as identified below:

1. Foundation: To safety its objectives, foundation must be

designed to satisfy certain requirements as to provide suitable

support and stability for the structure.

To safety sustain and transmit to the combined deal, imposed

and wind loads in such a manner as not to cause any

settlement or other movement which would impair (weaken) the

stability or cause damage which or any part of the building or

any adjourning building.

- It must be taken down to such a depth as to safeguard the

building against the swelling shrinkage and or freezing of the

subsoil (especially on clay soil).

- It must be constructed to be capable of resisting any sulphates

attack and any deteriorate (harmful) matter present in the

subsoil.

2. Floor: The floor structure must fulfill several functions and

design considerations as follows:

- Provision of a uniform level surface; except in specified cases

for drainage purposes, floors are normally designed and

constructed to serve as a horizontal surface to support people

and their furniture, equipment and machinery.

- Sufficient strength and stability: The floor structure must be

strong enough to safety support the lead load of the floor and

its finishes, fixtures, parathions and services and the

anticipated imposed loads. This is largely dependent on the

characteristic of the materials used for the floor structure such

as timber, steel or concrete. It is also expected that the floor

should be stiff and remain stable and horizontal under the dead

half of the floor structure and the imposed loads. For stability

there should be adequate vertical support for the floor structure

and the floor should have adequate stiffness against gross

deflection under load. Providing reinforcement where

necessary.

- Exclusion of Dampness from the inside of a building

(Ground floor),

There is usually an appreciable transfer of moisture from the

ground to the floor. To prevent this depends on the nature of

the subsoil. A concrete slab could be used on a gravel coarse

grained sand base where the water table is relatively below the

surface. A water concrete slab, where the subsoil is clay base.

- Thermal insulation (properties): The ground floor should be

constructed to minimize the transfer of heat from the building to

the ground or the ground to the building. The hand core and

the damp proof membranes will assist in preventing the floor

being damp and feeling cold and so reduce the transfer of heat.

In some cases the floor could be insulated against excessive

transfer of heat.

- Resistance to sound transmission and absorption (sound

insulation), Timber floors will more readily transmit sound than

a mass concrete floor, so the floors between dwellings (upper

floors) are generally constructed of concrete. The reduction of

impact sound is best affected by a floor covering sound as

carpet that readers the sound of footsteps on either a timber or

a concrete floor sound absorption of floor can also be improved

by carpet.

- Resistance to fire:- Timber floor provides lesser period of

resistance to fire than a reinforced concrete floor. Upper floor

should be constructed to provide resistance to fire for a period

adequate for the escape of the occupants from the building

(normally 1 to 6 hours).

3. Wall: Classification and design conveniently divide into two

categories; external and internal construction. Most external

walls support the upper floors and roof and most external wall

are self-supporting only functioning as a means of dividing

space for the building into rooms and coo pertinent it must also

fulfill other design consideration as:

Strength and stability, the wall should sagged by carrying its

own weight and the structural loads placed upon it. The

strength of the wall will depend on the strength of the material

of the wall and the thickness it can carry. The stability of a wall

may affect by foundation movement, eccentric loads

(floors/roof) acting on the centre of the wall the thickness,

lateral forces (wind), and expansion due to temperature and

moisture changes.

To assist weather, particularly during cold and the

exclusion of rain

This depends on the exposure of the wall to wind. The

behaviour of a wall excluding wind and rain will depend on the

type of material used in the construction of the wall and how

they are bonded. This wall must be designed so that the rain is

not absorbed to the inside force of the wall, by making the wall

of sufficient thickness, and by applying an external facing of

rendering, or by building cavity wall.

Resistance to sound transmission and sound abortion, the wall

should be designed to resist the impact of noise. Sound is

transmitted as airborne sound and impact sound. Example of

airborne sound from radio and voices. Example of impact

sound is slamming of a door or footsteps on a floor. The

heavier and more degree the material of the wall, the more

effective it is reducing sound. Insulation against impact sound

consists of some absorbent materials that cushion the impact of

carpet on a floor.

Durability: The wall is designed with due regards to the

exposure of the wall to driving rain and with sensible….. it

should be durable for the anticipated life of the building and

should require little or no maintenance repair.

Fire Resistance and thermal properties: The wall should be

resistance to collapse, flame penetration and heat transmission

during a fire (normally 1 – 6 hrs). to maintain reasonable and

economical conditions of thermal comfort in building, walls

should provide adequate insulation against excessive loss or

gain of heat, have adequate thermal storage capacity –

lightweight materials are used where loss of heat will be

encountered. While dense materials are used in continually

heated buildings.

Roof: The structure is designed principally to prevent

penetration of inclement (severe) weather and to provide and

adequate barrier against heat loss. Other considerations

include an adequate appearance, the facility to absorb thermal

and moisture strength and stability to accommodate

maintenance and rain loads expatriate.

Door: the Fundamental purpose of a door is to provide access

into or out of a building and between the various compartments

within a building. Additionally, the following functions are to be

fulfilled, the extend depending on the building type and

purpose; the door should be designed to have sufficient

strength, shape and stability so as to provide adequate security

and privacy. A door should also function in excluding weather

(wind and rain), containing some waterproofing properties. Door

also act as barriers against fire, sound and thermal movement.

Window: The functions of a window are to admit daylight,

provide natural ventilation and to exclude wind and rainwater. It

also acts as thermal and sound insulators. In some

circumstances, the view from a window provides an important

function as relief and pleasant relaxation from daily internal

routine (view). It contains some fire resistance properties and

can act as a means of escape in case of fire outbreak.

Stairs: A stairway is initially designed to provide an effective

means of access between different floor levels. A secondary

function of considerable importance to provide a practical

escape route in the event of fire.

WEEK 2

SITE PREPARATION

Before the commencement of actual building construction, there is the

need to conduct certain preliminary site activities. This is to enable the

building team have foreknowledge of a site. Some activities which

preceded the actual building construction are

Site investigation ( ) and organization (layout)

Site welfare facilities

Storage and protection of materials

Site fencing and hoarding

Site clearance and excavation

Leveling and setting out

Ground water control.

1. Site Investigation and Organization – A preliminary examination or

survey of the job is made during the designing and post-designing

stages of a project. The survey enables the contractor or the engineer

to precisely have an idea about the site and assess if there are

peculiar problems to the proposed contract. It is this initial

understanding of these problems that the engineer will use to design

the building to suite the site. Similarly, the contractor could plan and

organize his activities, sufficiently to achieve success and minimize

time. This is done by producing a site layout plan and placing

equipment and materials in specific positions for easy reach, handling

and utilization.

Provision of services during site organization to a building site maybe

temporary where the work is transient (short period), e.g. construction

of highways. Elsewhere the services will be a permanent necessity

and should be installed accordingly to avoid repeating the work, e.g.

building construction. It is often advantageous to the contractor to

provide these services particularly electricity and water, from where

permanent installation could be mace. Other temporary services may

include access to site, watchman services, dust control (by watering

ground area), site clean (debris clearance), etc.

Some considerations to be given by the contractor during

reconnaissance and layout prior to constructional works are

(a) Availability and means of access to the site whether by road,

rail or waterway.

(b) Availability of suitable materials/equipment and spare available

for erecting plant and or storing materials around the site.

(c) Availability of space to erect temporary site offices and welfare

facilities.

(d) The effect of vibration on adjacent structure when the

construction involves using heavy/massive equipment (e.g. in

piling) should be considered.

Sub

-Roa

d

Acce

ss R

oad

SITE LAYOUT PLAN Existing Building

Main Road

Store and

Storage

Watchmen

PROJECT men

Mixer

Crane

Dumper

Ag

gre

gate

an

d S

an

d

Bu

sh

Toilet

Ca

nte

en

Watchmen

Dressing

Room Tech. Room

Engineering

Room Clinic

(e) The availability of water and power supply should be

ascertained and the rate of payment investigated.

(f) Knowledge of the nature and type of soil, and the level of water

table is important as the way necessitate subsoil drainage and

cause flooding.

(g) The local planning authorities should be approached to

ascertain whether there is any special or significant restriction

which could adversely affect the development of site (e.g.

underground cables).

(h) Valuable information can be obtained by talking with the local

inhabitants of the area.

(i) Any special condition that may limit work in anyway should be

noted and taken care of e.g. weather or climatic condition.

2. Subsoil Exploration (Trial boreholes) – Trial boreholes to determined

the nature of a subsoil is an important part of an early site

investigation. The building design and structural loading can be

related to the detailed and thorough examination of the subsoil bearing

potential (ability to withstand load). Preliminary examination may be

with trial pits excavated by spade or a hand anger. When more

detailed information is required, a powered anger is more effective.

The depth of boreholes can be several meters deep for high rise

buildings, and boring can be at random or regular intervals. Samples of

subsoil can be extracted loose or distorted, or undisturbed in steel

tubes. They are recorded on a borehole log, and samples are then

taken for laboratory analysis to establish the moisture content, bearing

capacity and chemical composition.

3. Site Welfare Facilities – The provision of shelter and accommodation

for taking meals and deposition of clothes is a basic requirement on

all sites. The builder should provide a hut for workmen so that meals

and short rest can be taken, and also for storage of clothing not

required for work during the day and protective clothing at night. The

mass room or canteen should be convenient for washing facilities.

Adequate wash basins, troughs and showers with soaps and towels

are required. (an isolated sanitary facility with water closets is also

required). Provision for first aid is also very important, and every

contractor must provide first-aid accommodation to include a couch,

stretchers, bandages, blankets, equipment, etc a trained person in

first-aid treatment is to be available on site during working hours.

4. storage and Protection of Materials – Materials such as cement,

timbers, bricks and blocks should be protected from weather by

storing in a shed or well stacked in a suitable position on the site,

where they will not be liable to damage and are adequately protected.

Electrical and plumbing (sanitary) fittings should be kept in a locked

shed to avoid theft or breakage. Proper storage is necessary

because saturated cement with time sets and becomes hardened

resulting to wastage. Saturation also affects the mortar or concrete

strength. Water is readily absorbed by timber causing deformation

and rot, this should be avoided. A saturated brisk or block will be very

difficult to handle. They should be well protected.

5. Site Fencing and Hoardings – A permanent fence or a temporary

hoardings will be required around the site. This is a barrier made of

block wall, wooden or mental stalk or rail or wire in some cases used

old zinc to provide security and protect equipment and materials, and

to keep out intruders. It also protections the ugly sight of construction

and preserves the beauty till completion. The hoardings are removed

after the completion of the project. The hoardings should be well

erected and in sage order so as not to cause injury to workers or

passé.

6. Site Clearance excavation to soil – The site should be cleared of the

bushes, shrubs, trees, etc. which are on the building position and

around the storage and temporary facilities area. The roads should

be grubbed up and completely removed.

Before any building is erected, it is essential that the area to be

occupied by the building has the vegetable top soil removed from site

completely or placed on one side, and spread level over areas after

completion of the project to provide gardens. The organic content of

the vegetable soil may be injurious to concrete, and so it should

never be used for backfilling, or making up levels under the building.

The path of excavation of topsoil is normally 150mm.

Leveling, land clearance and stripping of the topsoil are all easily

achieved with a bulldozer.

7. Ground Water Control: - Excavation and sample boreholes frequently

reveal and locate a level of saturation within a few meters below the

surface. This is known as the water table and it varies with season.

Excavation below the water table will be difficult and the strength of

any concrete placed in water will be seriously affected. A pre-

knowledge of this fact helps the contractor to be equipped and

prepare with his diesel powered water pump for the temporary

removal of water during excavation and concreting.

8. Setting Out and Leveling – After the stripping of the topsoil and

general site leveling, it is important that the structure is built in the

correct position as shown on the architect’s drawings. The position of

a building is marked out with string lines and pegs to indicate

foundation trenches and walls. The frontage line (building line) is an

imaginary line shown on the site plan, or determined by the local

authority, set back from the centre line of the road way.

WEEK 3

METHOD OF SETTING OUT

There are three main methods of setting out

345 method

Builder’s square and

Theodolite methods

(a) 345 Method - This is based on the mathematical principle

that any triangle with the sides in the ration of 345 is a right

angle. The method is as follows first you determine the building

line and established one corner of the building by driving a peg

at that point. A tape is used to measure a distance of 3m along

the building lien and a second peg is established with a nail on

top. The ring of the tape is held over the second peg with the

12m mark of the tape. With an assistant and with the 3m mark

of the tape around the corner peg, the tap is then stretched out

to give the position of the third peg at 7m mark. Now a line can

then be extended through third peg to give the width of the

building. The line extended should be perpendicular or 900 to

the building line. The above procedure is also carried out for

the rest corners and any possible intersection within the

building. To check the accuracy of the four-sided figure formed,

the diagonals should be measured to be equal in length.

(b) Builder’s Square Method This is similar to the 345 method, but in

this case instead of using a tape a steel builder’s square or a large

timber square and a line are used to establish the squareness of the

corners. Two pegs (P1,P2) with nails at their tops are driven along the

building line. One at the corner. A line is then held along the two

pegs tied at P1 going round the corner peg P2, the building’s square is

then held with its external angle point at nail of the corner peg, while

the line on P1, P2 is touching one entire side of the square. This line

is then pulled round P2 to touch the other entire side of the builder’s

square. Holding the line firm a third peg is the driven down where the

line touches the top of nail of P3.

The diagonals (a)(a) should be equal in length to ascertain the accuracy of the setting out operation.

Building line

a

a P2 P1

P3 7m

3m 0.12m

(c) Theodolite Method This is the most accurate method of setting out

of buildings. It involves using a surveying instrument called the

Theodolite. The theodolite is equipped with a telescope and cross

STEEL SQUARE

Ranging line

TIMBER SQUARE

String line

Nail

Builder’s Square

P3

P2 P1 P1 3 P2

4

P3 5

Building line

Timber peg

Diagonal should be equal

hair for sighting and ranging, with an internal graduated readings in

degrees for establishing bearings (horizontal and vertical angles).

The method is as follows

I. Mount and set the instrument at point A, sight the telescope, range

and peg out E and B to establish the building line.

ii. Turn the theodolite screws and adjust the degree readings to 0.00.

Turn the telescope of the instrument on the tripod stand towards the

right axis until you can sight 900 00” wide. The instrument clamp sight

the telescope and range to established and peg out points F and C.

iii. Transfer the instrument to point C, and follow the same procedure at

A, range A and F, set the angle 0.00”, turn towards the right axis to

sight and obtain 900 and to establish points G and D.

iv. Point H could be established by using a measuring tape.

B

H

E A

F

C G

Building line

WEEK 4

EXCAVATION

Excavation in building construction is simply the act of removing or digging

out earth (soil) from the ground for the purpose of laying foundation,

construction of floor, basements, etc. The earth is originally dug up to

specified depth, width and length.

The technique of excavation is largely determined by sensitivity of the site

to vibration, intensity of work, availability of plant and the subsoil

composition.

There are basically two methods of excavation, the manual method and the

mechanical method.

The manual method involves the use of hand tools such as spades

diggers, hand augers, pickers (rakes) and other manual implements for the

purpose of excavation. The manual method is regarded as a cheap means

of excavation, it is virtually obsolete and time consuming. The method can

be used only in very small buildings, e.g. garages or house extension,

where the site is inaccessible to excavating plant, and where archeological

remains are discovered and particular care is necessary. The method is

also used for trimming excavations by mechanically means where outward

projections and deviations are specified.

The mechanical method is a process of using mechanical plant and

equipment for excavation. This use of mechanical plant and equipment

saves considerable man-hours, and are standard features on all sites. The

type of plant varies with the nature of work and the different construction

stages. Plant can commonly be used for

a. Striping clearance and light demolition

b. Striping of top soil

c. Trench excavation

d. Basement excavation

The principal types of plant machine used for excavation are

a. Bulldozer

b. Loader/backhoe

b. Loader/Backhoe (Backacter) – The backachter/loader has on one

end a toothed bucket and hydraulic boom which extend out and

excavate towards the cab. This end is used mainly for excavation of

trenches, basement and ditches. The other is equipped with a

faceshovel loader for loading excavated loose earth into a dumper, a

tipper or lorry.

c. Scrapper – The scrapper contains a larger bowl with covered cutting

edge for stripping soil. It is used in very large sties, airfield of

highway.

Bowl Drop d.p.r

Cutting edge

d. Dragline/Grab Crane – Where the volume of excavation is large, the

crane- mounted dragline is preferred. The bucket is swinging forward

to penetrate the subsoil and dragged back towards the cab. Deep

excavation into granular soils is more effective with a grab or

„clamshell‟.

EARTHWORK SUPPORT

When excavations (trench) are dug in water saturated soils, it is important

to provide supports to the side of the excavation. This is done to prevent

the walls from caving-in (collapse) causing severe injury or death to those

required to work inside the trench. Apart from causing injury and death, it

will be additional cost to the builder to re-excavate and renew the damaged

work in the trench. Should the sides support collapse, timber and steel are

normally used for trench. The process of supporting trenches is generally

termed “planking and strutting”. The amount of support, side and system of

arrangement of the various timers depends on

a. The type and nature of subsoil to be supported

b. The depth of excavation.

c. The length of time the trench is to remain open

d. The time of year or climatic conditions prevailing when the trench

is excavated.

Timber is often the most convenient material for shallow trenches. Steel

interlocking polings are often used for deep water-logged subsoil.

Adjustable steel struts are also more convenient and have considerable re-

use value for all depths of excavation.

The timbering members used in trench support are as follows

i. Poling board – There are of 1.0 to 1.5m in length to suit the trench

depth, and they vary in cross-section fro 175 by 35mm to 225 by

50mm. They are placed vertically and against the soil of all the sides

of excavation.

ii. Wallings – These are longitudinal members running the length of the

trench and supporting the poling boards. They vary in sizes from 175

by 50mm to 225 by 75mm.

iii. Struts – These are usually squared timbers, either 100 by 100mm or

150 by 150mm in sizes. They are used to support the wallings, which

in turn holds the poling boards in position. Adjustable steel struts are

also in great use.

iv. Sheeting – These consist of horizontal boards abutting one another

to provide continuous barrier when excavating in loose soils and

common size for the sheeting is 175 x 75mm and there is overlap of

about 150mm at the point of connection between two stages.

Alternatively, steel interlocking poling with adjustable steep struts are

used.

Timbering in loose subsoil

Sheeting

Strut

Wedge Poling

Adjustable Steel Strut

In moderately firm ground, the timbering consists of a series of poling

boards which are widely spaced at about 60mm centres, supported by

wallings and struts. In shallow trenches, the poling boards would probably

only be needed at the about 1.8m centres with each pair of poling board

strutted individually with a single strut and no walling.

Timbering in Moderately Form Soil

In loose or saturated soil, a continuous horizontal sheeting supported by

pairs of poling boards and struts about 1.8m may be used. Alternatively, a

Walling

Poling Board

Strut

continuous length of poling boards or runners supported by walling and

struts may be used. If the trench exceed more than 1.5m in depth, it is

necessary to step up the timbering so that the lower stage fits inside the

upper section.

CONTROL OF GROUND WATER IN AN EXCAVATION

There are several methods available for controlling ground water during

excavation work. Some of the methods deals with lowering, while others

involves water exclusion from the site. Some of the methods employed in

the control of ground water during excavation work include

i. Plumbing Method ii. Dewatering

iii. Electro osmosis iv. Grouting

v. Soil stabilization

1. PUMPING FROM WELL OR (SUMP)

Pumping from sump is the most used for used of ground water

control since it is economical to install and maintain and can be

applied to all types of ground conditions.

The only problem is of the movement of the soil due to settlement

and there is also the risk of instability at the formation level of the

excavation. Where the excavation goes through permeable soil and

continued into impermeable soil, it is better to form a drain at the line

of interception to carry water in the sump. With this system a sump is

constructed at one corner of the site which forms a well point

continuous pumping of water.

The pump which is mounted on the ground level has one

disadvantage due to imitation in the design of suction lift to some

types of pumps. The suction lift of most pumps is at 7.5m – 9m. For

deep excavation where the depth exceeds 9m, the pump will have to

be placed in the excavation or on a level suitable for the suction lift.

2. DEWATERING

This consists of lowering the water table over the area of the site and

is satisfactory for depths up to 16m, it is particularly suitable where

running sand is encountered for once the water has been removed in

the ground, the sand become relatively stable. The equipments used

for the separation comprises of

i. Jetting pump, for driving down the well points

ii. Suction pump iii. Header pipe and

iv. Rises pipe.

The operation of dewatering is carried out by first jetting the well

points into the ground, this is done by securing each well points to

38mm diameter riser pipe at the top of which there is a connection by

a hose to the jetting pump. The assembled well points are held on

the ground and the pump operator delivers water under pressure until

the point penetrates the ground. The well points on reaching the

desired depths, the points are “sounded in” the hose of the top of the

well point is determined from the jetting point and attached to 150mm

diameter header pipe has coupling joint at 760mm 1m intervals so

that rises can be jointed at this spacing. For dealing with large volume

of water in loose ground or lose sand. The equipment can be used

for 2 main types of work.

i. The ringing system ii. The progressive system for

trenching.

i. Ringing System – In this system, the building site is encircled

with needle points and for single stage work, until permit

building work to be done at depth up to 6.5m where excavation

of 9m – 12m are required 2 stage work is adopted. For this, the

top are in dewatered and excavated first, the area is then

ringed at this intermediate stage for dewatering the corner

depth.

ii. Progressive System – This is suitable for dewatering along

the line of trenches before excavation. The wall points are with

draw when work is completed and filled in dead of the work.

The header pipe in laid along the ink of the proposed trench as

near as practicable. In different ground the pipe is placed in the

trench and supported on struts.

WEEK 5

FOUNDATIONS

A foundation is defined as, that part of a structure which is in direct contact

with the ground to which super imposed loads and dead loads are

transmitted or received. It is also an integral part of a building which

transfers the structural load from a building safely to the ground. Many at

times, during the construction of a building, the load on the foundation

gradually increases and eventually, this will result in settlement if the

settlement is slight and uniform throughout the area of the building, no

damage will occur to the building.

But if the settlement is extensive and unequal, serious damage may result

in the form of cracked walls, distorted doors and windows and in some

cases failure may be completed by the collapse of the building.

Selection of foundation types and design depends on the total building load

and the nature and quality of the subsoil. It is essential to achieve a

satisfactory balance between the building load and subsoil characteristics,

otherwise overstressing of the subsoil will lead to excessive building

settlement and serious structural defeats.

The purpose (importance) of foundation is to distribute the weight of the

structure to be carried over a sufficient area of bearing surface, so as to

prevent the subsoil from spreading and to avoid settlement of the structure.

A foundation should safety sustain (Carry) and transmit to the ground the

combined dead load, imposed load and wind load, without impairing the

stability of any part of the building.

A foundation is designed to support a number of different kinds of loads.

(a) The DEAD LOAD of the building, which is the sum of the weight of

the frame, the floors, roofs, and walls, electrical and mechanical

equipment and the foundation itself.

(b) The LIVE (IMPOSED) LOAD, which is the sum of the weights of

people in the building, the furnishings, sanitary fixtures and the

equipment they use, snow, ice and rain load on the roof.

(c) The WIND LOAD, which can apply literal, downward, and uplift load

to a foundation.

All foundation settle to some extent as the soil around and beneath them

adjust itself to the loads. Foundation settlement in most buildings is

measured in millimeters. If the total settlement occurs roughly at the same

rate from one side of the foundation to the other, no harm is likely to be

done to the building. This is because all parts of the building rest on the

same kind of soil. But if differential settlement occur (when the building

occupies a piece of land that is underlain by two or more areas of different

types of soil with very different load bearing capacities) in which the various

columns and load bearing walls of the building settle by substantial different

amounts, the frames of the building become distorted, floors may stapes,

walls and glass may crack, doors and windows may be difficult to open,

etc. the primary objective of foundation design is to minimize differential

settlement by loading the soil in such a way that equal settlement occur

under the various parts of the building.

SOILS IN FOUNDATION

Where the foundation of a building is on rock, no measurable settlement

will occur, whereas the building on soil will suffer settlement into the ground

by the compression of the soil under the foundation load. Some settlement

on soil foundation cannot be avoided, because as the building is erected,

the load on the foundation increases and compresses the soil. This

settlement must be limited to avoid damage. Bearing capacities for various

rocks and soils determined and should not be exceeded in the design of

the foundation to limit the settlement.

Soils are classified with regards to their size, density and nature of the

particles. Soil can be classified into three broad groups namely coarse

grained non-cohesive, fine grained cohesive and organic soils.

Coarse grained non-cohesive soil – This consist of coarse and larger

siliceous product under pressure from the loads on foundation. The soil in

this group compresses and consolidates rapidly by some rearrangement of

the particles and expulsion of water.

A foundation on this type of soil settles rapidly by consolidation of the soil,

as the building is erected, so that there is no further settlement once

building is completed.

Fine grained cohesive soils – This consists of natural deposits of the

finest siliceous and aluminous product or rock weathering such as clay.

Clay is smooth and greasy to touch, it shows high plasticity, dries slowly

and shrinks appreciably on drying. Under pressure of load on foundations,

clay soils are gradually compressed by the expulsion of water from the soil

so that the buildings settle gradually during building work and this

settlement may continue for some years after the building is completed.

Firm shrinkable clays suffer appreciable shrinkage on drying and expansion

of firm clay under grass extends to about 1 metre below the surface and up

to 4m or more below large trees. Building on shallow foundations should

not be close to trees, shrubs and trees should be removed to clear a site

for building on firm clay subsoil. This is because gradual expansion or

contraction (shrinkage) of the soil will cause damage to the building by

differential movement. This is as a result of the intake of subsoil water by

the tree roots.

Organic soils – Such as peat are not generally suitable foundation for

buildings. Foundation of this type soil are normally carried down to a

reliable bearing stratum.

TYPES OF FOUNDATIONS

There are four principal types of foundation strip, pad, raft and pile

foundations.

1. STRIP FOUNDATION

This type of foundation is a continuous level support for load bearing

walls. It is usually made of a continuous strip of concrete of 136 mix,

and may be reinforced (126) mix for poor subsoil or high loading.

The continuous strip serves as a level base on which the wall in built

and should be of such width as to spread the load on the foundation

to an area of subsoil capable of supporting the load without stress.

The width of a concrete strip foundation depends on the bearing

capacity of the subsoil, the less the width of the foundation for the

same load. The minimum width of a strip foundation is 450mm and

least thickness is 150mm. they are suitable for low-rise construction.

SECTION THROUGH A STRIP FOUNDATION

(a) Wide Strip Foundation

This type of foundation is used where the structural loading is very

high or relative to the subsoil bearing capacity. It is generally

cheaper to reinforce the concrete strip to reduce the equivalent

strength thickness to carry and spread the load.

2P + W

P x P

G.L.

Solid brick wall

(b) Deep Strip Foundation

This type of foundation has two applications

i. Narrow strip or trench fill

ii. Reinforced deep strip

The Narrow strip (trench fill) is designed to save considerable

structural construction time and where the nature of the subsoil such

as clay requires a considerable depth of 900mm, it is used to

excavate foundation trenches and fill them with concrete up to just

below the ground level say 2 brick coarse before the finished ground

level.

Wall G.L.

150m

1.2m

Reinforcement

Reinforce deep strip are acceptable alternative to wide strip

foundation for soft clay subsoil conditions. The depth should be at

least 900mm to avoid effect of shrinkage and swelling and about

400mm wide to provide sufficient support for the wall. Reinforcement

is required to take care of compressive stress as subsoil may develop

voids in long periods of dry weather due to volume change.

400

900

P

G.L.

2. PAD FOUNDATION

These are isolated pairs or column of brick, masonry or reinforced

concrete often in the form of a square or rectangle pad of concrete for

supporting ground beans, and in turn supporting walls. It is very

economical to use pad foundation where the subsoil has poor bearing

capacity for some depth below the surface, rather than excavating

deep trenches and raising wall in strip foundations. It is also used

where isolated columns are specified, especially in framed buildings.

The spread of area of this type of foundation depends on the load on

the soil and the bearing capacity of the subsoil.

400

900

G.L. Wall

Reinforcement

FOUNDATION PLAN SHOWING EXCAVATION WORK FOR PAD

CONSTRUCTION

SECTION THROUGH A PAD FOUNDATION

A B C

A 2

3

Reinforcement

column

Reinforcement

Pad foundation

3. RAFT FOUNDATION

In soft compressible subsoil, such as soft clay or peat subsoil. It is

necessary to form a raft foundation to spread over the whole base of

the building. Raft foundation consists of a raft of reinforce concrete

under the whole of the building design to transmit the load of the

building to the subsoil below the raft. Relative settlement between the

foundations of columns is avoided by the use of a raft foundation.

The two types of raft commonly used are the flat raft (solid slab raft)

foundation and wide toe raft (beam and slab raft) foundation.

Mat Reinforcement for pad foundation

building

Ground beam

Four members of starter bar

G.L.

(a) Flat Raft (solid slab raft) Foundation

This comprises of a reinforced concrete slab of uniform

thickness cast on a bred of blinding concrete and a deny proof

membrane, under the whole area of the building. This type of

foundation is used on loose subsoil with reasonable bearing

capacities for small buildings, such as houses. The slab

normally reinforced top and bottom.

(b) Wide Toe Raft Beam and slab rift ) Foundation

50 Blinding Damp proofing

membrane

Reinforcement

G.L.

Cavity wall

Floor finish

50 spread (cement

& sand)

100 mass concrete

floor

150 reinforced

concrete raft

This is like a reinforced concrete floor with down stand beams

called toe. It is used when the ground has poor compressibility.

The reinforced concrete edge beam is designed to support the

outer skin of the brick work or columns. The strengthened

beam collect loads from the walls or columns and transmit

these loads to the slab cast integrally with the beam, and the

slab in turn spread the loads over the whole area of subsoil

below the building.

Reinforcement

Damp proof membrane

100 hardcore

Blinding

Reinforced concrete raft

Screen

Floor finish

Cavity wall

G.L.

4. PILE FOUNDATION

Pile foundations are used where the subsoil has poor and uncertain

bearing capacity and in poor drained area where the water table is

high and there is appreciable ground movement. Piles are usually

employed because in these types of subsoil, it might be necessary to

excavate beyond 2m to meet a stable stratum. And it is uneconomical

to consider normal excavation beyond about 2m below the ground

level. The pile column of concrete either cast insitu or precast driven

into the ground to transfer the loads through the poor bearing soil to a

more stable stratum. Boring is undertaken by a powered auger. The

pile foundations are normally employed in the construction of bridges

and oil platforms on seas.

Short Bored Piles - These are used for small buildings on shrinkage

clays where adjacent trees could appreciate volume change in the

subsoil. Short bored (short length) piles are cast in holes by hand or

machine auger. The piles support reinforced concrete ground beams

on which wall are raised.

Reinforced

Concrete beam

Building

Poor grade

subsoil Piles

G.L. Sound bearing strata

Depth up

to 4m

G.L.

Reinforced

concrete beam

Concrete pile

Hardcore

Sand blinding

Ground floor slab

FOUNDATION ON SLOPING SITES

Walls foundation on sloping sites are normally constructed at one level or

stepped. Where the slope is slight the foundation may be at one level with

floor raised above the highest ground level. Where there is a greater slope,

it is usual to cut and fill so that the wall at the highest point does not act as

a retaining wall and there is no need to raise the ground floor above the

highest point of the site. The process of “cut and fill” is normally practiced

when providing foundation for walls on sloping sites. This is the operation

of cutting into part of the higher part of the site and filling the remaining

lower part with the excavated material or with the imported materials (for

Depth determined by resistance to

driving

G.L.

Reinforced

concrete beam

Steel sleeve

Hardcore

Sand blinding

Ground floor slab

Hollow fibre reinforced concrete shell

Solid concrete shoe

280

fill). It should be noted that cutting extends beyond the wall at the highest

point to provide a drained dry area behind it.

Where a building extend some distance up an appreciable slope, it is usual

to use stepped foundation to economize in excavation and foundation

walling.

Foundation at one level

Stepped Foundation

G.L.

Consolidated fill

under solid floor

Consolidated fill

under solid floor

Steeper slope

Ground

Shallow slope

STEPPED FOUNDATION

METHODS OF REINFORCEMENT IN FOUNDATIONS

1. GROUND BEAMS

Reinforced concrete

building slab

Ground

bearing slab

Selected soil

fill

Compacted

hardcore Existing G.L.

Top soil removed

Slab of raft reinforced top

and bottom

Section through reinforced concrete ground beam and slab raft with upstand

beams

R.C. Beams

Reinforcements

Floor construction with precast R. C. Beams bearing

on upstand beams on raft.

Raised timber or concrete floor

formed on raft

Reinforcements

R.C. Slab reinforced

top and bottom R.C. Beams

G.L.

Reinforcements

Helical building

hand

Lifting hole

Press steel forms

Corner for R.C.

Main reinforcement

Stirrups to

Lifting hole

Chilled cast iron

shoe

Cover

Forks

Links

Section of a

body of pile

Main reinforcement

Cast iron shoe

Cast iron shoe

End of tube

Cage of reinforcement

Steel

Concrete consolidates as

the tube is withdrawn Finished reinforcement

concrete pile

METHODS OF CONSTRUCTION OF VARIOUS FOUNDATIONS

1. STRIP FOUNDATIONS

Construction of strip foundation is carried out by first excavating the

ground to specified volume to remove soil to receive concrete. A

fairly dry weak concrete is the placed to specified depth inside the

foundation already containing a hardcore base (if necessary). This is

to act as a working base and to receive the oversite concrete. Where

a reinforcement or mesh are required, they are placed on mortar

blocks or concrete blocks (biscuit) on the blinding to give the cover for

concrete. A leveling instrument or a building plumb and short iron

pegs (off cuts) are then used to establish the tip level of the

concreting in the trench at intervals throughout the length of the

foundation trench. Concrete is then mixed and is poured into the

trench over the reinforcement until it reaches the established pegs.

As pouring is done a potter vibrator is used to vibrate the concrete to

remove the voids from the concrete. The concrete is then left to set

and harden and cured with water after one day of easting for at least

7 days.

2. PAD FOUNDATION

This is similar to the strip foundation construction, except that instead

of excavating in strips, deep hollow square or rectangular trenches

are dug. The provision of reinforcement for the base of the pad

interlock with the vertical reinforcement going up for the columns.

This is to ascertain a continuous interlocking support, strength and

stability between the pad and the concrete column. Where steel

stanchions (columns) would be placed on the pad foundation,

steel/iron bolts or steel plates are embedded in the foundation during

construction, where the stanchions or columns would be placed

(bolted or welded) on the pad foundations.

Concrete is then mixed, poured or placed, vibrated and cured as in

the strip method. In some cases formwork are sometimes used to

protect the sides and give shape to the pad.

3. RAFT FOUNDATION

The raft system involves the excavation of the whole base area of the

building and where ground beams are specified, is further excavated

below the raft slab foundation. Formwork is made to support the sides

of the foundation and insitu slab.

The placing of reinforcement for the slab and beam interlock or

overlaps. The placing of concrete and curing is as in the strip

method.

4. PILE FOUNDATION

(a) Bored Piles

This method is an insitu concrete construction. It consists of drilling

or boring a hole by means of earth drills or mechanically operated

augers which withdraws soil from the hole for casting of pile in

position. Usually steel lining tubes are lowered or knocked in as the

soil is taken out, to support the sides of the board pile.

Reinforcement are placed, concrete is then placed and compacted in

stages. As the concrete pile is cast the lining tubes are gradually

withdrawn

The disadvantages of this method are that it is not possible to check if

the concrete is adequately compacted, and there may be no

adequate cover to the concrete reinforcements.

(b) Precast Concrete Piles

As the name implies, these are precast either round, polygonal or

square concrete, steel or timber piles which are driven into the

ground by means of a mechanically operated drop hammer attached

to a mobile piling at a calculated predetermined „set‟. The word „set‟ is

used to describe the distance that a pile is driven into the ground by

the force of the hammer.

To concrete the top of the precast piles to the reinforced concrete

foundation at the top, 300mm of the length of reinforcement of the

pile is exposed, to which the reinforcements of the foundation is

connected.

Precast driven piles are not in general use on sites in built up area

(unrestricted area) due to

i. Difficulties in moving them through narrow streets

ii. Nuisance caused by the raise of driving piles and vibration

caused by driving the piles may damage existing adjacent

buildings.

WEEK 6

DAMP PROOFING

SUBSTRUCTURAL WORKS

RISING AND SEEPAGE OF GROUND AND UNDERGROUND WATER

If water is to rise of seep in a wall or floor, a constant supply must be

available at the base and side of the floor and wall. Water rise by an

upward capillary pull between the masonry pores. On building sites with

high water table and on slopping sites where water may run down to the

building, site concrete, floors and walls are likely to get damp by the

respective rising and seepage or moisture/water. The obvious indication of

rising damp and seepage is the dark staining above the skirting, bored on

the interior of a wall. This however, should be carefully checked to avoid

misconception of defective plumbing, leaking gutters/down pipes, and

defective chimney. Another indication of rising damp is the appearance of

white salty deposits on both faces of a wall called efflorescence. It is drawn

from the ground as the dampness rises, and they combine with any salt in

the masonry.

Rising and seepage into building is due to the lack of provision of damp

proofing materials, or may also be due to several possible construction

faults (i.e., in the cases where damp proofing materials are provided).

Some of these faults may include the following

The arrows ( ) indicate rising and seepage of ground

and underground water

IMPORTANCE OF DAMP PROOFING IN SUBSTRUCTURAL

WORKS

Damp roofing is the principle of preventing moisture entering buildings and

causing dampness which might be as a result of water/moisture rising up

the wall and floor from the ground forced through the structure, or seeping

through the forces of walls.

d.p.c

d.p.c

Bridging though

mortar painting

Paving or drive finished above

d.p.c

Earth stacked

against wall

Rendering

over the d.p.c

One chief essential requirement in building construction is to construct a

structure which is habitable and dry to live in. A dry building is unsightly

and causes damages to some components of the structure affected.

Most structural works are intended to be dry habitable. Any moisture

movement upwards from the ground through the substructural works to the

superstructure hampers the functional requirements of the affected building

components, and this reduces the quality of construction. The intended

purpose/use of the structure may also be defeated. Concrete is to some

degree permeable to water and will absorb moisture from the ground. A

damp oversite concrete slab may cause deterioration and damage in

moisture sensitive floor finishes such as timber or P.V.C. A damp oversite

concrete also will be cold and draw appreciable heat from rooms causing

cold.

Damp proofing helps the prevention of moisture rising up the floor or

seeping through walls, causing efflorescence and damage to the walls and

floor finishes.

Generally, damp proofing helps to maintain the quality, strength, stability,

durability and resistance to moisture/water of structures. It also helps to

maintain an appreciable room temperature. And to provide protection to

final finishing materials to concrete floors. A damp proofing materials must

be incorporated in concrete floors.

PROCESSES OF DAMP PROOFING

The process of damp proofing involves the provision of a continuous layer

of horizontal damp proof coarse (d.p.c) at about 150mm above finished

ground level in walls whose foundation are below the ground. And the

provision of a damp proof membrane (d.p.m) for the entire area on top is

between or under the oversite concrete slab.

The d.p.c should be impenetrable and continuous for the whole length and

thickness of the wall and be at least 150mm above finished ground level.

This is to prevent or avoid the possibility of a build-up of materials against

the wall acting as a bridge for moisture seeping through the wall.

A d.p.m should be impenetrable to water and touch enough to withstand

possible damage during laying of screeds or floor finishes. Application of

d.p.m. on irregular surfaces tend to puncture the membrane, so the

application of this materials should be done on a bed of sand or ash of

12mm thickness. The d.p.m may be on top, sandiviched in or under the

concrete slab.

All d.p.c, in external walls should unite with d.p.m in, on, or under the

oversite concrete. This may be affected by either laying the membrane in

the concrete at the same level as the d.p.c in the wall or by uniting the

membrane and d.p.c, laid at different levels with a vertical d.p.c.

Narrow trench fill foundation

d.p.c and p.p.m at same level

Concrete strip foundation

d.p.c and d.p.m at different level

150 concrete oversite

50 blinding

d.p.m

50 screed

d.p.c

Cavity wall

d.p.c abd d.p.m Overlaps

Hardcore

Hardcore

d.p.c abd d.p.m Overlaps

d.p.c

Cavity wall

Cavity wall

d.p.m

100 concrete oversite

Bed of sand or ash

d.p.m

FUNCTION OF A DAMP PROOF COURSE

Damp proof course is a layer of material capable of preventing the

penetration of moisture. It is laid on top of all walls at a distance of 150mm

above the finish ground level.

A d.p.c is an unbroken layer of impenetrable material on most foundation to

prevent the moisture absorbed from the soil rising and causing dampness

in the wall. Moisture penetration and rising dampness constitutes health

risks and cause discomfort to the inhabitants of the building.

Generally, d.p.c helps the preservation of wall finishes especially at the

base of the walls. d.p.c also provides protection against the dampness

arising from during rain. d.p.c reduces the tendency of the moisture to rise

up to the wall finishes, like rendering and painting at crack blister, peel,

flake, slow drying, etc.

TYPES OF DAMP PROOFING MATERIALS

1. Damp proof membrane materials

a. Hot, pitch or bitumen

b. Bitumen sheets/solutions/tar

c. Mastic asphalt

d. Polythene sheet

2. Damp Proof course

a. Flexible d.p.c materials

(i) Lead

(ii) Copper

(iii) Bitumen

(iv) Polythene sheet

b. Semi-Rigid d.p.c materials

(i) Slates

(ii) Bricks

BASEMENT CONSTRUCTION

METHOD OF CONSTRUCTION OF BASEMENT PROCEEDS IN

STAGES

1. Excavation begins at ground level and the sides are supported by

timbering.

2. This continues until the required dept is reached.

3. Foundation is cast and walls started. Timbering is removed

progressively and the space backfilled.

4. The wall reaches ground level all around the excavation.

5. The soil inside the walls can then be removed, if necessary.

BASEMENT EXCAVATION

The excavation for deep basements started at ground level, as the holes

becomes deeper a decision base to be made about the method to be

employed.

If ramp of earth is left in position, tipper tracks can use it to get into and out

of the hole. This depends on the length of the excavation, as it must be

able to accommodate a ramp of about 200 slope. Weather condition and

type of soil may also be considered as this may affect the use of the ramp

by loaded vehicles.

The ramp may be removed finally. If this is done by an excavator, with the

soil being removed by bucket and crane, the excavator will have to be

hoisted out on completion. If vehicles cannot drive out of the excavation,

the soil will have to be loaded into buckets, hoisted to the surface and

loaded on to trucks. The excavator is finally lifted out by crane. Where

excavation is not very deep, hand excavation may be used.

Various types of earth moving and excavation plant are available for use in

different circumstances, e.g. bulldozer shovel back actions and drag-line

grab crane excavators, loader and truck.

PRINCIPLE OF TANKING IN BASEMENT WORKS

Tanking is a system of forming a continuous waterproofing lining usually in

asphalt round the walls and floor of a basement as a barrier to rising and

penetrating dampness. The term tanking can also be used to describe a

continuous waterproofing lining to the walls and floors of substructures (e.g.

basement structures) to act as a tank to exclude water. This principle is

known as Basement taking.

The traditional material for tanking is mastic asphalt which is applied and

spread hot in three coats to a thickness of 20mm for vertical and 30mm for

horizontal work. Joints between each laying of asphalt in each coat should

be staggered at least 75mm for vertical and 150mm for horizontal work with

the joints in succeeding coats. Angles are reinforced with two coats of fillet

of asphalt.

Asphalt is usually applied to the outside face of structural walls and under

structural floors so that the walls and floors provide resistance against

water pressure on the asphalt, and the asphalt keep water away from the

structure.

Where the walls of the structure are on site boundaries and it is not

possible to excavate to provide adequate working space to apply asphalt

externally, a system of internal tanking may be used.

An internal lining is rarely used for new buildings because of the additional

floor and wall construction necessary resist water pressure on the asphalt.

Internal asphalt is sometimes used where a substructure to an existing

building is to be water proofed.

HARD CORE

This is an application of suitable material suck as broken bricks, stones and

tiles, clinker, gravel, quarry waste, which are required on the building site to

fill hollow oversite concrete work. On wet sites, it may be used to provide a

firm working surface and to prevent contamination of the lower part of the

wet concrete during compaction.

The particle materials should be hard and durable, not subject to decay or

breakdown by weather or chemical attack, and it should be easily placed

and well compacted. The hardcore should be spread until it is roughly level

and round until it forms a compact bed for the oversite concrete. The

hardcore bed is usually 100 to 300mm thick. It is spread to such thickness

as required to raise the finished surface of the oversite concrete.

Generally, the hardcore bed serves as a solid working base for building and

as a bed to receive oversite.

BLINDING

Is a process of providing a layer of dry concrete, coarse clinker or ash over

the hardcore before placing the oversite concrete. Before the concrete is

laid it is usual to blind the top surface of the hardcore. The purpose is to

prevent the wet concrete running down between the lumps of broken brick

or stone, as it would make easier for water to seep through the hardcore

and could be wasteful of concrete. To blind or seal, the top surface of the

hardcore a thin layer of very dry coarse concrete can be spread over it, or a

thin layer of coarse clinker or ash can be used. the blinding layer, or coat,

will be about 50mm thick, and on it the site concrete is spread and finished

with a true level top surface.

USE OF ANTI-TERMITE TREATMENT IN FOUNDATION WORKS

A problem in tropical climates is the possibility that timber maybe attacked

by termites. The common termite or white ant forms colonies in the ground

where a nest housing the queen is found. The termites can enter a building

through the ground looking for timber to consume. The junction of the wall

and floor is a particularly vulnerable point.

There are some precautions which can be taken to reduce the risk of

termite attack.

1. The area around the building should be inspected for termite nests,

which should b dug out and treated with insecticide.

2. During excavation work for the foundation and hardcore bed, the

exposed soil should be treated with insecticide, in an anticipation of

termite attack.

3. The ground floor concrete should be raised above the adjourning

ground level and should project beyond the outer wall face.

WEEK 7

FLOORS

Floors are structural parts of a building. They are usually designed to be of

either a timber or concrete work. Generally, in building construction floors

are designed and constructed for the flowing primary purposes (function):

a) Provision of a uniform level surface: - Unless otherwise specified,

floors are constructed to provide a uniform level surface, this is done

primarily to sufficiently provide adequate support, comfort, stability

and strength to carry people, their furniture, equipment and materials.

b) Exclusion of Dampness from inside of the building (especially

ground floors): - Floors also function as to prevent the passage of

moisture rising up/surpring through foundations/walls and causing

dampness and discoyort inside the building, this is normally attained

by using a d.p.m.

c) Thermal Insulation: - Floors minimize the transfer of heat from the

building to the ground of the building. A floor also serves to conserve

or reduce heat as the case (situation) may require. In this case

insulations or special finishing materials are used.

d) Sound Insulator: - Floors also serve as a barrios to transmission of

airborne sound and reduce impact sound, (especially upper floors)

normally concrete is preferred to timber because timber readily

transmit sound than concrete where timber are used they are

normally insulated with weight material (by filling the spaces between

the timber joists)

e) Fire Resistant: - in addition to the above functions, floors (especially

upper floor) are resistant, to fire to some considerable degree. They

provide resistance adequate for the escape of the occupants from the

building in times of fire outbreak.

f) Compatibility with the Surface Finish: - The purpose of a floor is

also to provide an adequate and acceptable surface finish to meet the

need of the user, with regards to appearance, comfort, cleanliness,

stability and safety.

GROUND FLOORS

There are primarily two types of ground floors solid ground floor and

raised timber ground floor.

A) SOLID GROUND FLOORS

There are normally constructed in-situ concrete. Solid concrete

ground floors have three principal components; hardcore, a damp

roof membrane and a layer of dense concrete. To construct these

types of floors, hardcore is compacted onto the reduced ground level

after excavation.

To prevent cement ground loss from the superimposed concrete

layer, or to protect a damp roof membrane from fracture, the hardcore

is blinded with a 25mm layer of sand.

The damp-proof membrane maybe positioned below the concrete

slab, upon the sand blinding polythene, sheet is the most popular

material, although bituminous sheet is acceptable. Alternatively, the

d.p.m. maybe sandwiched between the finishing their screed and the

structural concrete slab. In this particular case, cold or hot application

of bituminous solution in three layers with final layer sprinkled with

sand to bond to the screed overlay.

The concrete slab is of 100 – 150mm in thickness, composed of

cement, fine aggregate and coarse aggregates in the ratio of 1:3:6 to

provide a minimum strength specification of 1hr/mm2 at 28 days with

coarse aggregate of 38mm. A mix of 1:2:4 is preferred when using

coarse aggregate of 19mm size. A tamping bar is used to compact

and level the concrete to the specified depth-provided by short iron

pegs with finishing provided by cement/sand (1:3) screed.

B) SUSPENDED (RAISED) TIMBER GROUND FLOORS

This system of providing ground floors in buildings is now virtually

obsolete due to the escalating cost of the materials and skilled labour

required for their installation. Some few centuries ago houses were

constructed with timber ground floors raised 300 or more above the

site concrete or earth. This was done to have the surface of the

ground floor sufficiently above the ground level to prevent them being

cold and damp during winter.

Construction of this type of floor is made up of selected timber

platforms of hardwood floor boards nailed across timber joists, and

the joists in wall plate bearing on ½B thick sleeper walls, built directly

off the site concrete 1.8 apart. Sleeper walls are generally built three

courses of brick high, and are also built honey-combed to allow fire

circulation of air below the floor, to prevent wood decay. Air bricks are

also provided along external wall also to aid the circulation of air.

Component Parts of the raised timber ground floor construction:

a. Honey-comb sleeper wall: - sleeper walls are ½B thick built directly

off the site concrete about 1.8-2.0m apart. These sleeper walls are

generally built at least three courses of brick high and sometimes as

high as upto 600mm. The walls are built honey-combed to allow free

air circulation below the timber floor members.

b. D. P. C.: - This is spread and embedded on top of the sleeper walls

to prevent any moisture rising through the site concrete and sleeper

walls to the timber floor.

c. Wall Plate: - This is a continuous length of softwood timber which is

embedded in mortar on the d.p.c. The wall plate is bedded so that its

top surface is level along its length and also level with the top of wall

plates on other sleeper walls. This timber member is usually 100 x

75mm and is laid on one 100 face so that there is 100 surface with on

which the timber joists bear. The function of a wall plate for timber

joists is two-fold: -

(i) It forms a firm level surface on which the timber joists can bear

and to which they can be nailed.

(ii) It spreads the point load from joists uniformly along the length

of the wall below.

d. Floor Joists: - These are rectangular section softwood timbers laid

with their long sectional axis vertical and laid parallel spaced from

400 to 600 apart.

Floor joists are from 38 to 50 thick and 75 to 125 deep timber boards

are laid across the joists and nailed to form a firm level floor surface.

e. Floor Boards: - For timber, floor boards are usually 16,1921 or 28

thick and from 100 to 180mm wide and up to 5.0m in length. The

edges of the board maybe cut square or plain edged, though this

being the cheapest of cutting and fixing them, but boards tend to

shrink causing ugly cracks and the edges to open up. The usual way

of cutting the edges of floor boards is by providing a torque on one

edge and a groove on the opposite edge of each board, commonly

termed T and G. The boards are laid across the floor joists, cramped

together and nailed to the joists with two nails to each board bearing

on each joist.

f. Ventilation using air bricks: - In order to avoid deterioration of timber

under the floor board or suspended timber ground floor, there is need

to allow air circulation under the floor system. In order to achieve this

special air bricks must be provide at the external walls of the building

and adequately spaced. The purpose of these air bricks is to cause

air to circulate under the floor and thereby preventing stagnant air

which is likely to induce dry rot fugues to grow and causing word

decay.

In summary therefore, construction of the raised timber ground floor

can be achieved the assemblage of the above conform placed on a

concrete slab on a hardcore based.

SUSPENDED (UPPER) FLOORS

There are two main types of upper floors, timber upper floors and

reinforced concrete upper floors. Though timber upper floor

construction is about half the cost of a similar reinforced concrete

floor, concrete floors are still preferred because of their better

resistance to fire and to sound transmission and supports heavier

loads.

1. TIMBER UPPER FLOORS

There is no much difference in construction between the timber upper

floor and suspended timber ground floor. The only noticeable

difference is the elimination of sleeper walls in the upper floors, which

consequently involved the use of layer timber section for the floor

joists.

i. Strutting between Joists: - Timber floor joists spanning more than

3.0m are strutted at mind-span or 15m spacing to resist buckling and

deformity. This is done to safeguard and prevent cracking of the

plastered ceiling work due to excessive shrinkage and movement of

the joist. The herringbone strut arrangement using 50 or 38mm

square softwood struts is most efficient, but solid strutting is often

used for easier and quicker installation. Solid strutting consists of

short lengths of timber of the same section as the joist which are

nailed between the joists either in line or staggered. This is not

usually so effective as the herringbone system, because unless the

short solid lengths are cut very accurately to fit to the sides of the

joists they do not firmly strut between the joists. As with herringbone,

between the first and the last joists and adjacent walls folding wedges

are used to firmly locate the strutting.

ii. End Support for Floor Joists: - The floor is normally framed with

softwood timber joists, with maximum economical span of between

3.6 and 4.0.

The required depth of joists depends on the total load. For

stability, the ends of floor joists must have adequate support from

walls or beams. There are various methods of supporting the ends

of joists in order to sustain the imposed loadings.

a) The ends of the joists are treated with preservatives (to avoid

decay) and are built into the brick walls. This method requires

cutting and packing of trick work in order to bring the top of the

joist on the same plane, care must taken to prevent joist

protinding into the cavities of the cavity wall and providing a

bridge for moisture penetration. Alternatively timber floor joists

can be built into wall to bear on a wall plate of timber or metal,

which are along the length of the wall beneath the joists, this

assist in spreading the load from the floor along the length of

the wall and also as a level bed on which the joists are placed

and nail in position. The wall is then raised between and above

the floor joists.

b) End support for the joists can also be attained by the use of

galvanized steel floor hangers, which are built into brick or

block courses so that they project and support the ends of the

joists. This is the best method of providing supports to joist

from external walls as it avoids building timber into walls.

As an alternative to hangers, timber floor joist maybe supported by

a timber wall plate carried on iron corbels built into walls, or brick

courses corbelled out from the wall. The disadvantage of these is

that they form a projection below the ceiling.

iii. Floor Boards: - As with timber ground floors, the boards usually

19 or 21 thick have T & G edges core cramped up and nailed

across the floor joists, with the heading joints staggered.

(ii) GALVANIZED

STEEL FLOOR

HANGERS

Hangers built into wall

to support joists.

(iii) STEEL CORBELS BUILT

INTO SUPPORT WALL

PLATE

Wall plate

support joists

Corbels built into wall to

support wall plats/joists.

(IV) WALL PLATE SUPPORTED

OR TWO CORBELS OF BRICK

CORBEL WALL PLATE

Two-course brick corbel

brick wall plate

2. REINFORCED CONCRETE UPPER FLOORS

Reinforced concrete floors have a better resistance to damage by fire

and can safely support greater super imposed than timber floors of

similar depth.

(a) Monolithic Reinforced Concrete Floors: - As the name

implies a monolithic reinforced concrete floor is an unbroken

solid mass of concrete between 100 and 300 thick, cast in-situ

and reinforced with steel reinforcing bars.

Construction of monolithic reinforced concrete floor consists of

a temporary CONFERRING (consists of timber/steel platforms

erected at ceiling level supported on timber or steel beams and

posts) to support the concrete while it is still wet and plastic for

7 days. The top surface of the platform is then painted with

mould oil to prevent the wet concrete from adhering to the

platform, so that timber platforms can be removed easily. Small

tiles or blocks (biscuit) are then cast 15-25mm thick depending

on the specified concrete cover. These are placed at frequent

centres on the platform. These tiles (specer blocks or biscuits)

are tied to/and support the steel reinforcement, and ensures

that the mesh will have the specified cover for the concrete.

The concrete is the placed of cast on the centering to the

required thickness, and it is compacted, vibrated and leveled off

care must be taken that vibration is not overdone so that most

of the cement is hot brought to the surface, thereby reducing

the strength of the mix. The concrete is then cured for 7 days

before the centering is removed.

b) Precast Self-centering Floor System: - centering or formwork used

to support the monolithic reinforced concrete floors tend to obstruct

and delay building operations. So for emergency projects where time

is an important factor, self-centering concrete floors are used. This

1B wall Timber

support

Timber

chartering

½B

partition

Timber

formwork

Main bars with

bent-up ends

Distribution

bars

Biscuit 1B wall

Raised brick work

above floor cast

Concrete floor built in

Concrete floor

cast in-situ

type of floor is made of precasted concrete beams which are usually

manufactured in yards and are transported to the site for fixing. They

serve as floors when they are raised and placed in position with their

ends built into brick walls. Once in position they require is support

other than the bearing of their ends on walls or beams. There are a

wide range of precast self-centering floor systems:

i. Rectangular hollow cross-sectional beam floor units, closed

spaced.

ii. Inverted channel sections, closed spaced

iii. Solid precast ‘T’ section beams with hollow lightweight concrete

infilling blocks.

HOLLOW CONC. BEAN FLOOR

WEEK 8

WALLS

Walls are vertical and continuous solid structures, usually constructed from

materials such as clay, stone, concrete, timber or metal.

Walls can be classified with respect to their functional requirements as

internal and external walls. They can also be defined as load bearing

(carrying imposed loads from roofs and floors in addition to their own

weight) and non-load bearing (eg portion), non-load bearing is with respect

to the structural requirements. There are variably two types of walls, solid

wall and framed wall. A solid wall (Masonry wall) is constructed either of

blocks of brick, burned clay, stone or concrete.

These are laid in mortar to overlap to form a bond (bonding) or as a

monolithic (eg concrete wall). A frame wall is constructed from a frame of

small sections of timber, concrete or metal joined together to provide

strength and rigidity, and between the members of the frame thin panels of

some material are then fixed to the frames to fulfill the functional

requirements of the particular wall.

THE FUNCTION OF A WALL IS

(1)To enclose and protect a building, and also serve as a means of (2)

dividing space within a building walls serve (3) as protection against wind

and rain, and to (4) support floor and roofs and to some extent to (5)

conserve heat within the building. Walls can (6) serve to protect the

building against fire, excessive heat, and to resist or minimize the

transmission and absorption of sound especial solid block walls. Framed

walls usually of less weight than solid block walls are normally used for

partitioning existing structures so as to minimize the total load of the

building. The use of framed walls is preferred where there is little

consideration for sound transmission. Note that no material for wall

concrete fulfils all the functional requirement of a wall with maximum

efficiency.

BRICKS

Bricks are small blocks manufactured from burnt clay that can be handled

with one hand, and its length is twice the width plus one mortar joint. Blocks

made from sand and lime and blocks made of concrete manufactured in

clay brick size are also called bricks.

The standard size is 215mm x 102.5mm x 65mm which with 10mm mortar

joint becomes 225mm x 112.5mm x 75mm.

65

215

102.5

STANDARD

BRICK

FORMAT SIZE

There are various types of bricks of the same standard format are classified

with respect to the material used, composition, extent of mixing and curing,

duration and amount of forming applied. Some of these of bricks are:

commons, facings, engineering bricks, semi-engineering bricks,

composition of clay, flattons, stocks, marts, Gautts, clay shale bricks,

calcium silicate bricks, flint-lime bricks, and hollow, perforated and special

bricks.

Some special applications and features work require bricks to be reduced

in size or reshaped. Specials are either cut from a whole brick, or purpose-

made (manufactured) by hand in hardwood moulds.

KING CLOSER

¼ Brick

½ Brick

½ BAT OR SNAP

HEADER

¾ BAT

¾ BAT

½ Brick

1 Brick

BEVELED CLOSER

Queen Closer

¼ Brick

Some examples of purpose-made (manufactured) special bricks

Plink Header Plink stretcher

Squint Angle

Angle brick Dogleg brick

Birds month Cant Double Cant

Half round Coping Saddleback coping

Single bull nose

bull nose mitre Double bull nose

Perforated brick Cellular pressed brick

WEEK 9

BRICK BONDING

To build or construct a wall of brick or blocks, it is usual to lay the bricks in

some regular pattern. The brick courses or rows in a wall are arranged to

ensure that each brick overlaps or bear upon two or more bricks

immediately below it. The process of laying the bricks across each other

and binding them together is called bonding. The amount of overlap and

the part of the brick used determined the pattern or bond of brickwork.

Bonding of bricks can also be defined as the arrangement of bricks in

which no vertical joint of one course is exactly over the one in