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UNESCO-NIGERIA TECHNICAL &VOCATIONAL EDUCATION
REVITALISATION PROJECT-PHASE II
YEAR I- SE MESTER I THEORY/PRACTICAL
Version 1: December 2008
NATIONAL DIPLOMA INBUILDING TECHNOLOGY
BUILDING CONSTRUCTION I
COURSE CODE: BLD103
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TABLE OF CONTENTS
WEEK 1: BUILDING COMPONENTS(1.1) Building components
(1.2) Major building components(a) Foundation(b) Floor(c) Wall(d) Door(e) Windows(f) Roof
WEEK2: PRELIMINARY SITE ACTIVITIES(2.1) Site activities that precede Actual building construction
(2.2) Provision of facilities of on site
WEEK3: SITE ORGANISATION AND LAYOUT(2.3) Site layout and organization
WEEKK4: SETTING OUT OF BUILDING(2.4) Setting out of building
WEEK5: EXCAVATION(3.1) Method of Excavation(3.2) Tools used in manual Excavation
(3.3) Equipment used in mechanical Excavation
WEEK6: EARTHWORK SUPPORT(3.4) Method of Earth(3.5) Foundation
WEEK7: FOUNDATION(3.6) Importance of foundation to building(3.7) Types of foundation soil(3.8) Simple calculation of the area of concrete foundation
WEEK 8: TYPES OF FOUNDATION(3.9) Types of foundation and their application
WEEK 9: TYPES OF FOUNDATION (CONTINUED)
WEEK10: METHODS OF REINFORCEMENT IN SUBSTRUCTURES(3.10) Methods of reinforcement in Substructures
WEEK11: CONSTRUCTION OF FOUNDATION
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(3.11) Method of construction of foundation
WEEK12: DAMP PROOFING(4.1) Rising damp and seepage of ground water in building(4.2) Damp proof course (DPC) and damp proof membrane (DPM)(4.3) Function of damp proof courses
WEEK13: MATERIALS USED FOR DAMP PROOF COURSE(4.6) Materials used for damp proof course
WEEK14: BASEMENT TANKING(4.4) Tanking in basement work
WEEK15: HARDCORE(4.7) Hardcore layer(4.8) Blinding(4.9) Termite Treatment
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WEEK 1: BUILDING COMPONENTS
(1.1) Building Components
A building acts as an enclosure for the activities that of on within, it building will protect the
occupants, equipment or goods housed within from the various of he external climate (rain,
wind, sun etc). For a building to act as enclosure, it must have external walls and be covered by a
roof. The roof will normally rest on the walls and be support by them. The walls in turn, will
need a firm base or foundation to be built upon, which will transfer their weight and that of the
roof to the ground beneath.
To make the building usable, the internal space enclosed by the external walls and roof may need
to be sub-divided into room by the introduction of horizontal dividers between storeys, the
floors, and vertical dividers between rooms, the internal walls. Stairs or lift can provide accessbetween storeys. Doors can provide access to the building and to each room within the building.
Daylight and ventilation can be introduced into the building by the provision of windows in the
external walls or roof. All these part of the building are referred to as building component or
elements
(1.2) Major Building Components
The major building components are as listed below. Foundation Floor Wall Door Window Fenestration (Other openings) Roof Ceiling
Foundation
The function of the foundation is to transmit the load from the building finally to the soil. This, it
must do without excessive settlement and compression of the supporting soil layer.
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Functional Requirements of Foundation Ability to carry loads with a minimum movement Adequate width to safely transmit the loads on it to the supporting soil layer
Functions of Foundations Foundation provides suitable support and stability for building Transmits to the ground all the loads that come on the building over a sufficient area of
subsoil
Prevents the failure of the building or uneven settlement.
The selection of foundation types is influenced by
The type of building The nature of the loading The site condition
Foundations are of many types but the more common ones include
Strip foundation Pad foundation Pile foundation Raft foundation
Fig.1.1.Strip foundation
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Floor
Floor can be defined as the horizontal structure which carries imposed and live loads in a
building and divides a building into storeys. It plays an important role in a building.
The most common material used for the construction of floors that will meet the requirement of
building regulations and local bye-laws are concrete and wood.
Functional Requirements of Floor Adequate strength and stability to support the loads that comes on it. Resistance to sound penetration Resistance to moisture penetration Thermal resistance Fire resistance Durability Hard wearing
Wall
This is usually the vertical continuous part of a building which encloses or protects the buildingor divides the building into rooms and compartments. It is made up of blocks, concrete, mortar,
stones, metals etc. types of walls include: Internal, External, Buttress, Sleeper, party, parapet
partition and cavity walls.
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Fig 1.2 Internal and external walls
Functional Requirements of Walls Openings for daylight and ventilation Fire resistance to provide security and stability in the event of fire Adequate strength to resist being crushed by the loads from floors and roofs they support Durability to withstand the condition under which it will function Adequate stability to resist other forces such as wind pressure and roof loads.
Door
A door is a movable barrier placed across an opening in a building that provides access into the
building or between spaces within the building.
Functional Requirements of Door Weather resistance Durability Fire resistance It must be easy to slide open and close
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Fig 1.3 Example of a Paneled door
Windows
Windows provide natural light and ventilation to the interior of a building while excluding rain
and insects.
Windows are usually made of timber, steel. But other materials such as plastics (uPVC) and
aluminium are also popular. Each material has its own advantages and disadvantages.
Functional Requirements of Window The minimum area of window in a habitable room should be 10 percent of the floor area The minimum opening area of the window in a habitable room should be 5 percent of the
floor area.
Adequate security against intruders
Adequate resistance to external weather elements
Provide privacy.
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Fig. 1.4 Parts of a window
Roof
This is the topmost covering in a building. It is done during the finishing of a building. It
prevents a lot of sound (minimizing incoming sound), dust, wind and rain and also it helps the
occupants cover their privacy.
Fig. 1.5 The main parts of the structure of a pitched roof .
Functional Requirements of Roof
Strength : of roof depends on the characteristics of the materials from which it is constructed and
the way in which they are put together in the form of a flat or some form of triangular frame.
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Stability: a roof is constructed to support the dead load of the roof structure and its covering,
insulation and internal finishes, snow loads and pressure of suction due to wind without undue
deflection or distortion. The dead load can be calculated from the unit weight of materials with
which it is covered, varying from the continuous impermeable layer of asphalt covering that can
be laid horizontal to exclude rain, to the small units of clay tiles that are laid overlapping downslopes so that rain runs rapidly to the covers.
Weather Resistance: A roof excludes rain through the materials with which it is covered;
varying from the continuous impermeable layer of asphalt converging that can be horizontal to
exclude rain to the small units of clay titles that are laid overlapping down slop so that rain runs
rapidly to the covers.
Durability: The durability of a roof is dependant largely on the ability of the roof covering to
exclude rain and snow. Persistent penetration of water into the roof structure may cause or
encourage decay of timber, corrosion of steel or disintegration of concrete.
Fire Safety: The requirements for control of spread of fire in schedule of the building
regulations for dwelling houses limit roof construction relative to the proximity of boundaries of
the site of the building by reference to the materials of roof covering.
Thermal Resistance: The materials of roof structures and roof covering are generally poor
insulators against the transfer of heat. It is usually necessary to use some materials which are
good insulator. Examples of such materials include light weight boards, mats or loose materials.
This is to provide insulation requirements to meet the building regulation for the insulation of
roofs of dwellings is a standard value of 0.25 where the SAP ceiling is over 60.
Sound Insulation: The resistance of a roof to the penetration of airborne sound is not generallyconsidered unless the building is close to a busy airport. The mass of the materials of a roof is the
main constructions in the reduction of airborne sound.
Test Questions
i. List the basic building components.
ii. State the functional requirements of four building components.
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WEEK 2: PRELIMINARY SITE ACTIVITIES
When a builder takes possession of a building site, he it usually provided with a site lay-out plan
and the drainages necessary for the erection of the building. Having taken over the site, the task
of preparing for and setting out the building can be started. Taking over the site includes having
the providing access road to the site to allow the movement men, machines and materials to the
site.
(2.1) Site Activities that Precede Actual Building Construction
The following activities precede actual building construction on site
Provision of access road Site clearance Provision of site offices and storage facilities Provision of site services
Site Clearance
The preliminary works on a construction project site usually begin after the sit facilities have
been set up. Clearing the site is essential. First, the vegetation such as bushes and shrubs should
be removed. The roots of trees and bushes must be dug out and cleared away.
Site clearance also may involve the demolition of existing buildings . demolition is a skilledoccupation and should be tackled by experts in that area.
The top soil should also be removed up to a depth of at least 150mm to remove any plant life and
decaying vegetable. The presence of vegetation and decaying materials means that the top soil is
easily compressible and cannot support building foundation. Top soil is however valuable as a
top dressing for gardens and may be disposed of in this manner
The site needs to be cleared of rocks and boulders in the area where the building will be set out.
If they are too large, then the boulders or rocks must be broken into smaller pieces and taken
away.
Site clearance is done by a combination of manual and mechanical means. The method adopted
will be determined by the overall economics which may be influenced by the scale of
development ant consideration for any adjacent buildings.
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(2.2) Provision of Facilities on Site
A well managed site should have facilities and services which will make the site functional and
convenient. On a building construction site, the following facilities and services should be
provided.
Temporary services : These include the provision of such services as water supply and,
electricity supply. Water is required on construction site for drinking and for the works. Where
the site is close to the public water mains, the water can be connected directly from the public
water mains to the site. The stand pipe should be located close to where the mixing of concrete
and mortar will take place. Where the site is far from the public water mains, water can be
supplied to the site with use of water tankers. The water can be stored in reservoir provided on
the site for such a purpose especially for the works.
An electrical supply for power tools, electricity can be supplied from the mains or a petrol
generator.
A telephone line should be provided which is secured so that it can only be used for official or
authorized calls.
Temporary access road: This should be provided to the site for the purpose of providing access
to vehicular traffic that will be bringing men and materials to the site. The access should be
constructed so that vehicles can enter the site in all weather. The access road can become part of
the permanent site services in the final design.
Site accommodation
A site should have an office and sheds for the workers on site to change their clothes and to take
rest on site during breaks from work and also have their meals.Site accommodation and similar facilities provided on a site depends on the number of people
that are working on the site.
Units of accommodation come usually in two forms
Sectional timber huts Mobile caravans or cabins
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Sectional timber huts are prefabricated for ease of dismantling and assembly to facilitate the re-
use on other sites. Huts of this nature should be designed, constructed and maintained with the
same care as permanent buildings to ensure their use for many years on a number of different
construction site. A well designed sectional hut should permit the addition of more bays to
increase the modular size by length and/or width. The anticipated use of each hut will govern theconstruction and facilities required. Offices need to be weatherproof, provided with artificial
lighting, equipped with furniture that might be required on the site. Similar basic construction
can be used for other units of accommodation such as meal rooms, and toilets should be provided
and equipped with the basic facilities.
Caravan and mobile cabins are available in a wide variety of sizes, styles, and application. The
construction is most times of a plywood clad timber frame suitably insulated and decorated.
They are usually made of modular system so that by using special connection unit any
reasonable plan size and shape is possible. The caravan and cabin are fully equipped with all the
necessary furniture light and heating units. The toilets can be connected to site services or be self
contained.
Material Storage: The type of storage facilities required on a construction site for any material
depends on the following factors
Durability ie whether it will need protection from the elements Vulnerability to damage Vulnerability to theft
Cement, plaster and lime supplied in bags form require a dry store free from draughts which can
introduce moist air and cause air set of the material. These materials should not be stored on the
site for long period of time on site; therefore provision should be made for rotational use so that
the material being used comes from older stock.
Aggregates such as sand and gravels require a clean firm base to ensure that foreign matter is not
included when extracting materials from the base of the stock pile. Different materials and
grades should be kept separated so that the ultimate mix batches are consistent in quality and
texture. Care must be taken to ensure that the stock piles are not used as refuse dump. The
moisture content of the aggregates should also be taken into consideration if it is exposed to the
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elements like rain, so as to allow for it in deciding the water cement ratio of the mix.
Bricks and blocks should be stacked in stable piles on a level and well drained surface in a
position where double handling is reduced to a minimum. Facing bricks and other coloured
bricks should be covered with tarpaulin to protect them from being discoloured by the weatherelements. Blocks should be stacked in such a way as to allow for air to flow freely through the
stack.
Timber absorbs water easily. To prevent undue moisture movement it should be stored in such a
manner that its moisture content remains fairly constant. A rack scaffold tubulars with a sheet
roof covering should be used to store timber. The sheet roof protects from rain and the various
sizes allow for free flow of air round the timber.
Ironmongery, hand tools and paints are some of the most vulnerable materials on site. Some
materials such as locks, power tools and cans of paint should be kept in a locked shed or inside
any of the completed rooms in the building under construction.
Test Questions
i. List the activities that precede actual building construction on site.
ii. What are the temporary services needed on construction site?
iii. How is storage provided for the basic materials on construction site?
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WEEK 3: SITE ORGANISATION AND LAYOUT
(2.3) Site Layout and Organisation
The building site can be considered a temporary factory, where the building is produced this
activity to take place the builder requires men, materials and plants. All these have to be
carefully controlled so that the men have the right machine in the most adequate position, the
materials stored so that they are readily available and not interfering with the general site
circulation a building and the total size of the site on which the building is to be erected.
Therefore is no standard size ratio between the free site spaces required considered as a
separation problem in terms of allocating space for men, materials and plant. To obtain
maximum efficiency there is an optimum way of laying out the site and also a correct amount of
expenditure to support the proposed site layout. Any planned layout should be reviewedperiodically and adjusted to suit the changing needs of the site activities. A careful consideration
of planning and control of this aspect of the building construction will reflect in the progress and
profitability of the building project.
Factors to Be Considered in Site Layout
Before any specific considerations and decisions can be made regarding site layout a general
appreciation should be obtained by conducting a thorough site investigation to formulate how the job will be executed. This will involve the assessment of the plants and equipment that will be
utilized to execute the work. Specifically the considerations include the following:
Access Consideration: this must be considered for both on and off site access. Routes to and
from the site must be checked as to the suitability for transporting all the requirements for the
proposed work. Access on site for deliveries and general circulation must also be carefully
considered so that vehicles delivering materials to the site will do so without difficulty or
delay. If is anticipated that large vehicles will be operating on the site it will be necessary to
consider the road surface required. If the road and the paved areas will form part of the
permanent work there should be constructed earlier in the work. If the anticipated traffic at
the end of the work is lighter than the one expected during construction enough protection
should be given to the road against the effect of the heavy traffic load.
Storage Considerations: the amount and types of material to be stored, security and weather
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protection requirements, allocation of adequate areas for storing materials and allocating adequate
working space around storage areas required, siting of storage areas to reduce double
handling to a minimum without impeding the general site circulation and/or works in
progress.
Accommodation Consideration: number and type of site staff anticipated, calculate size
and select units of accommodation and check to ensure compliance with the minimum
requirements of the relevant construction regulations. Select siting for offices to give easy
and quick access for visitors and at the same time giving a reasonable view of the site. Select
site for resting sheds and toilets to reduce walking time to a minimum without impeding the
general site circulation.
Temporary Services Considerations: what, when and where are they required? Possibility
of having permanent services installed at an early stage and making temporary connections
for site use during the construction period. Coordination with the various service providers is
essential.
Plants Considerations: the type and nature of plants and where they will be required on the
site are important. Whether the plants will be static or mobile. If static the most appropriate
position should be selected and hard standing should be provided. If mobile the circulationroutes should be checked for optimum efficiency and stability. Provision of space and hard
surface for plant maintenance should also be considered.
Fencing and Hoarding Considerations: distinction should be made between what is
mandatory and what is desirable. These will depend on vandalism record in the area, type of
fence or hoarding required possibility of using fencing which will form part of the permanent
work by erecting it at the early stage of the work.
Safety and Health Considerations: it should be ensured that all the above considerations
comply with the relevant construction safety regulations.
On taking over the site one of the first jobs is to layout the site boundaries as they are marked out
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on the drawings. The security fence should be set up around the site so as to control the
movement of people and materials. The boundary fence should have only one access so that
someone can check people in and out of the site. The site office should be located close to the
entrance into the site together with the site sheds where meals will be taken. The toilet on the site
should be located at one corner away from where it will constitute a nuisance and to alsoenhance privacy.
The aggregates should be stored close to where the mixing will take place which in turn should
be located close to where provision has been made for water storage. Generally materials should
be stored to close to where they will be put to use.
The site should be laid out in such a way that there will be free movement of vehicles around the
site in case it will become necessary to move materials using vehicles around the site.
Lay out of Construction Site
The layout of every site could be divided into
Administrative areas Construction areas
Administrative area: this will be the location of offices, stores, sub-contractors huts, canteen
and similar accommodation.
Construction area: this is the actual site of the building to be constructed, and it will be located
close to the consumable stores adjacent to the various buildings and equipment required for the
construction purpose. The layout of both these areas form an essential part of the early planning
in every construction work, the neglect of which will lead to delay in the initial progress of the
job leading to extra wastage of resources on the
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Fig 3.1 A typical site layoutTest Question
i. Discuss the factors considered in a construction site layout.
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WEEK 4: SETTING OUT OF BUILDING
(2.4) Setting out of Building
This is the transfer of information on the building drawing to the ground with high degree of
accuracy. When the site clearance is completed the setting out of the work may begin. It is
necessary to have a good knowledge of geometry in order to ensure accurate work. The first
tasked in setting out a building is to establish a base line from which the whole of the building
can be set out. The position of this line must be marks on site so that it can be re-established at
any time. The building line is frequently determined by the highway authority and in urban areas
it is often 8m from the back of the public foot path. If other buildings have been erected at the
area the building line can be determined from these existing buildings.
After the base line has been established, marked and checked the main lines of the building can
be set out, each corner being marked with stout peg. A check should then be made of the setting
out lines for right angles and correct lengths. The method of establishing of the right angle is
what the setting out sets out to establish in addition to the correct length.
Setting out Equipment
Measuring tape : before setting out any work the tape would be carefully checked for accuracy.Metallic lines tapes tend to stretch after they have been in use for sometime. The tape is to mark
the measurement on the profiles. It should be ensured that each measurement is taken from the
extended ring at the end of the tape.
Profiles : When setting out a building, it is an advantage if the line can be secured so that they are
well clear of the building line. The trenches can then be dug without interfering with the lines.
Timber profiles erected for this purpose consist of pegs driven into the ground and boards nailed
across them. The lines can then be stretched above the ground level well clear of any obstruction
and may easily be checked for accuracy.
Datum Pegs : Before starting the actual setting out of the building, it is essential to establish a
level on the site to which references pertaining to the levels of elements of work may be made in
the course of executing the work.
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In planned cities and town ordinance bench marks are established where a bench mark is far
from the proposed site, a levelling instrument such as covering, level can be used to transfer the
datum level to the site from where it can be distributed around the proposed site,
Datum pegs must be located where it would not be disturbed by the operation on the site.
Methods of Setting out a Building
There are three methods of setting out on small building sites. These are
Using 3,4,5 method Using the builders square Using the theodolite
Setting Out Using the 3,4,5 Method1. Mark out the building line from the road by measuring the required distance or by
stretching a line along the existing buildings to the proposed site. The building line is
then represented by the line shown as the ranging line, GG1 (in figure above).
2. Mark out the over all length of the building by driving in pegs at A and B along the
ranging line.
3. Produce two steel tapes measured and mark out four equal distances on the ranging line
starting from the corner peg at B (4m).4. Pull a tape measure from point B to C and ask an assistance to hold it ready with a
hammer and peg.
5. Pull the second tape from the fourth mark at D on the ranging to point E on the first tape.
6. The distance 5m on tape DE should coincide with point 3m to tape BEC to prove that the
angle B is 90 O (from Pythagoras theorem).
7. Repeat the same procedure to obtain the right angle from BAF, and mark out the overall
width of the building.
8. Establish corner pegs and erect profiles.
9. Mark the position or partition walls on the profile with either nails or saw cuts. Ranging
lines are stretched through these nails and the corner peg to establish the ground to
indicate the line of excavation for the foundation trenches.
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Fig. 4.1 Setting out of a building using the 3,4,5 method
Setting out a building using the builders square method
1. Find out the distance from the site boundary to the building line on the working drawings.
Use the tape measure to measure the same distance from the site boundary to the location
of the building line on the ground. Select a corner on the ground to be corner A.
2. Place a peg in the ground at corner A and hammer a nail into the top of the peg.
3. Repeat these steps to place a peg in the ground for corner B
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4. Tie the string between pegs A and B. Measure the distance between A and B. Check that
the distance on the ground is the same measurement as the distance on the drawing.
5. Repeat these steps for corners C and D
6. Measure the diagonals A-D and B-C (the two diagonals should be equal)
7. Use the builders square to check that the corners are at right angles.
Fig.4.2. Setting out using the builders square
Test Questions
1. List the three methods of setting out a building
2. List the equipment used in setting out a building
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WEEK 5: EXCAVATION
(3.1) Methods of Excavation
Excavation is done to receive the foundation that will be constructed for a building. This is done
after the setting out and marking out. Excavation can be done using two methods:
Manual method and Mechanical method
The choice of the method of excavation depends on the size of work. In small construction, it is
more economical to use the manual method, while large works will be economical to be executed
using the mechanical method of excavation.
(3.2) Tools Used in Manual Method of ExcavationThe manual method of excavation involves the use of the following tools
pick-axes used to dig up the soil shovels to remove the dug up soil spades to level the bottom of the excavation and to load into the wheelbarrow, Wheelbarrows to convey the excavated soil away from the excavation area.
(3.3) Equipment Used in Mechanical Excavation The mechanical method of excavation involves the use of mechanical plants which are capable
of doing more than one task. Examples of these are as follows:
Bulldozer : This is used to push the soil layer by layer to one side and pile it up nearby. A
bulldozer does not dig out or lift out the soil.
Backacter : This equipment digs down with a bucket on a jointed boom and scoops the soil
towards itself. Since the bucket is narrow it is useful for forming trenches. It can alsodeposit soil on trucks or Dumpers.
Mechanical Auger : This digs pile holes. It is a large piece of equipment which has a large
drill mounted on a platform. The auger drills a hole in the ground and lifts out a column of
soil.
Dump Truck : Used for the movement of soil over short distances. The body of the dump
truck tips forward and deposits the soil in the required position.
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Tipper Truck : This is a road vehicle used to remove large amounts of excavated materials
to locations away from the site. The body of the tipper truck tips up and empties the soil at
the back of the vehicle.
Fig 5.1 Plants used in mechanical excavation
Test Questions
1. What are the factors that determine selection of excavation method.
2. State the uses of two mechanical excavating plant.
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WEEK 6: EARTHWORK SUPPORT
(3.4) Methods of Earthwork Support
It is important to access how long an excavation can safely remain open without support for the
sides. If the weather is very dry then the lack of moisture may cause the soil to shrink, crack and
fall in. Generally the looser the soil the more it needs to be supported.
If the soil is very wet then the sides of the excavation may become unstable. In both cases it is
better to provide temporary supports to the sides of the excavation. Excavation on a confined site
may also need support in case heavy loads are placed or driven too close to the edges of the
excavation. Earthworks supports retain the size of excavation collapsed during the time the
excavation will remain open. The process of providing temporary support to the sides of anexcavation is referred to as timbering. It is sometime planking and strutting.
Timbering is to:
Protect the operatives while working in excavation Keep the excavation open by acting as a retaining wall to the sides of the trend. Prevent drainage to adjacent structures that could be caused by excavation Enable work to proceed within the excavation without interruption.
Components of Timbering
Timbering is made up of the following parts:
Polings: These are vertical planks supporting the soil. In sand or gravel, they should be
placed close enough to form a continuous timber wall. Depending on the soil type and
working conditions, they may be placed about 900 mm apart. The purpose of the wailing is to
keep the soil on the sides of the excavation from falling in.
Wailings: They are horizontal timber strips supporting the polings Struts: These are the timbers that span across the trench between the wailings. The struts
hold the opposite walls of the excavation in place.
Wedges: These are the pieces of timber used to maintain the pressure of the polings against
the soil. If the soil expands or shrinks while the work is carried out, the wedges may need to
be adjusted again.
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Factors to be Considered in Providing Supports to Excavation The nature of the soil Generally non-cohesive soils require more support than cohesive soil The depth of the excavation Shallow excavations need less support than deep excavation The width of the excavation The wide excavation needs to be supported in a different way
than narrow excavation.
The type of work to be carried out- Operation within the excavation will require working
space the amount required will depend on the operation involved.
The moisture content of the soil- soils require different amount of support as changes in their
moisture content occur.
The length of time the excavation will be left open- cohesive soils, in particular may dry out
and star to crumble if the excavation is left open for long periods of dry weather
The method of excavation hand excavation will require more support than machineexcavation
The support system used- different methods of excavation support can be installed before,
during or after the excavation.
The removal of the support system- different support systems can be removed either before
or after the excavation.
Moving materials into excavation the working space will need to consider the materials
being moved into and out of the excavation as well as the operating being carried out withinthe excavation
The proximity use of the land adjacent to the excavation for stacking materials over loading
of the ground by stacking materials close the excavation can cause stress on soils at the side
of the excavation. Similarly, large vehicle should be prevented from driving too close to the
excavation
Vibration of soils from construction operation or vehicle using adjacent road- excessive
vibration can cause soils to move, making the sides of excavation potentially less stable.
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(a) Timbering in hard soils (b) Timbering in firm soil
(c) Timbering in dry loose soils (d) Timbering in loose wet soils
Fig 1.7 Timbering in various types of soil
Another means of retaining the sides of an excavation without support by sloping the sides of the
excavation to the angle of repose of the soil, which is the natural angle at which the soil willremain stable without additional support. When a soil is tipped into a mound it settles to its
natural angle of repose. This angle will alter according to the type of soil and its moisture
content. Because the angle of repose can rather be shallow, this method of excavation support
does, take up a large amount of space on site and is therefore not frequently adopted. However,
this technique can be use on talk excavation.
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(3.5) Foundation
The function of any foundation is to safely sustain and transmit to the ground on which it rests
the combined dead, imposed and wind loads in such a manner as not to cause any settlement or
other movement which would impair the stability or cause damage to any part of the building.
Test Questions
1. List 4 consideration for providing earthwork support
2. Draw a typical earthwork support to a loose soil.
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WEEK 7: FOUNDATION
(3.6) Importance of Foundation to Building
The foundation
provides anchorage for the building carries the load of the building and safely transmits it to soils of better bearing capacity. provides a wide surface area to spread the load evenly across soil that can support the load.
(3.7) Types of Foundation Soil
The choice of foundation depends among other factors on the type of soil in which the
foundation is to be constructed.
Rock this is a very hard foundation soil. This kind of soil has a high load bearing capacity.
It can support strip foundation for a load bearing wall and a pad foundation for isolated loads
as those transmitted by columns and similar components.
Gravel and sand compact; suitable for pad, and strip foundation Clay stiff; suitable for pad and strip foundation. The depth of the foundation should be
taken to a depth where it will not be affected by swelling and shrinkage which sometimes
occur in clay soil.
Sandy clay Firm; suitable for strip and pad foundation. The foundation should be madewide enough taking into consideration the load bearing capacity of the soil.
Clay and silt Soft; suitable for raft foundation because of the low load bearing capacity of
the soil.
Soils are also classified into two categories which are
Cohesive soils in which the particles stick together and examples include silt, clay, clay and
silt Non Cohesive soil in which the particles do not stick together but are loose especially when
they are dry. Examples include rock, gravel and sand
Factors that Influence the Choice of Foundation.
The choice and design of foundation for building for building depends mainly on three factors
The total load of the building
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The nature and beaming capacity of the soil The amount of settlement produced by the loading.
The total load on the building
The total on a building is made up of dead load, line load and super imposed load. It is assumed
that a building imposes a uniform loading all around its perimeter. This is not strictly correct as
line load form floors and superimposed loading from the roofs will only be carried by the walls
that support these elements. To reduce the complexity of calculating individual loadings for
section of the external walls, it is easier to take the worst case scenario (i.e. the wall experiencing
the greatest sum of loads) and assume that all other walls are similarly loaded. If the load is
assumed to be uniform, then it is not necessary to add up all the loads for the entire perimeter of
the building. If a representative 1 metre length of the external wall is taken, then need the totalload on that section of wall can be determined and the foundation needed to support that section
of the wall can be determined and the foundation needed to support that section of wall can be
calculated. This design can then be applied to the rest of the foundation for the house.
The nature and bearing capacity of the sub-soil
The nature and bearing capacity of the subsoil ( the soil beneath the top soil) varies with the
types of soil, it is the degree of compressibility and he amount of moisture in the soil. Also,
cohesive soils, clays specification, can be subject to seasoned movement up to a depth of 1metre.
These soils exhibit shrinkage/contraction and swelling/expansion during dry and wet seasons
respectively.
The amount of settlement produced by the loading
Soil is compressible to varying degrees. As load is applied to the foundation the soil beneath the
foundation will be compressed, the water and air in the voids between the soil particles will be
squeezed out and the foundation will settle. This consolidation process will continue until the
forces between the particles are equal to the applied load. The speed of the consolidation is
determined by the speed of the migrating of water and air from between the soil particle.
Foundation built on sand on sand settles relatively rapidly, while foundation built on clay soil
settles more slowly and can last for a number of years.
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Soils that are close to the surface are likely to be more compressible than those at greater depth,
as deeper soil have been compressed by the weight of the overlaying soil. If the applied load on a
clay soil is reduced due to excavation, water tends to move to the unloaded areas and swelling
the soil will occur.
Peat and other soils containing a lot of organic matter shrink and swell easily as their water
content changes. They are very compressible and settle reality even under light loading. Made up
ground behaves in a similar manner unless the materials is well graded, carefully placed and
properly compacted in thin layers. Shallow foundation should not be used on sites consisting of
made up ground. Slight settlement should not cause problems to the structure of the building.
Excessive settlement may cause shear failure of the soil.
Settlement must also be uniform throughout the building; otherwise damage may result from
different settlement. The amount of different movement between parts of a building must be kept
within acceptable limits.
(3.8) Simple calculations of the area of concrete foundation
The size of foundation depends on two factors namely
Load being transmitted Bearing capacity of the soil under the proposed foundation.
The bearing capacities of soils are obtained from tables or from soil investigation reports.
Bearing Capacity of Strip Foundation
A strip foundation consists of a strip of concrete under a continuous wall that carries a uniformly
distributed load (i.e. the load from the wall to the foundation is uniform throughout the length of
the wall). The load on the foundation is therefore considered as load per metre run of the load
bearing wall.
Width of foundation required = load per metre run of wall (kN/m)
Bearing capacity of soil (kN/m 2)
Example 1
Calculate the minimum width of a strip foundation for a house where the total load from the wall
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is 50 kN/m and the soil bearing capacity is 150 kN/m 2.
Solution
Total load from the wall = 50 kN/m
Soil bearing capacity = 150 kN/m 2 Minimum width of the strip foundation = load per metre run
Soil bearing capacity
= 50
150
= 0.333m
Bearing capacity for pad foundations
A concentrated load may be supported by a column or free-standing brick pier on a pad
foundation. The size of the foundation should be related to the load carried by the column or pier
and the soil bearing capacity.
Example 2
The load on a brick pier that supports the load from part of the upper floor, wall and roof of a
two-storey building is 70 kN. The soft clay ground has a bearing capacity of 52 kN/m 2
Area of foundation in m 2 = Bearing pressure in kNBearing capacity of soil in kN/m 2
= 70/52
= 1.346 m 2
Test Questions
1. What are the factors that determine the size of a foundation?
2. Calculate the minimum width of a strip foundation that supports a wall that transmits a load
of 65 kN/m, given that the soil bearing capacity is 120 kN/m 2.
3. Calculate the minimum plan area of a pad foundation that carries a column supporting a total
load of 250 kN when the load bearing capacity is 200kN/m 2.
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WEEK 8: TYPES OF FOUNDATION
(3.9) Types of Foundation and Their Application
Foundations are classified into two broad categories:
Shallow foundations Deep foundations
Shallow Foundations
Shallow foundations transfer load of the building to a sub-soil at a level close to the surface.
They are nearly always the cheapest to construct and generally used where sufficient depth of a
strong soil exists near the surface of the ground. The foundation needs to be designed so that the
soil is not overstressed so that the pressure on the subsoil beneath the foundation is equal at all
points in order to avoid unequal settlement. The common types of shallow foundations are
Strip foundation Pad foundation Raft foundation.
Strip Foundation
Reinforced concrete strip foundations are used to support and transmit the loads from heavy
walls. The minimum thickness of a strip foundation is 150 mm. This may be of course, greater
where the projection of the edge of the foundation from the base of the wall is greater than 150
mm. A typical strip foundation is as shown in figure 8.1. The width of the strip should be at least
equal to three times the thickness of the wall it supports.
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Fig. 8.1 Strip foundation
The thickness of the foundation should be at least equal to the projection of the foundation from
the base of the wall so that the load transmitted from the wall will not be dispersed over an area
outside the width of the foundation as illustrated in figure 8.2. This is to prevent the shear failure
of the foundation.
(a) Lines of shear failure on wide and thin foundation (b) design of foundation to prevent shear failure
Fig. 8.2 Design of strip foundation to avoid shear failure
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The effect of the wall on the relatively thin foundation is to act as a point load and the resultant
ground pressure will induce tension on the underside across the width of the strip. Tensile
reinforcement is therefore required in the lower face of strip with distribution bars in the second
layer running longitudinally especially in soft soils and in wide strip foundation. The
reinforcement arrangement for a wide strip foundation is as shown in figure 8.3
Fig. 8.3 Wide strip foundation
In firm clays the sub-soil is capable of carrying substantial loads and may only require a
foundation to be slightly wider than the wall it is supporting. The foundation still needs to be
deep enough to overcome the problems of seasonal changes in moisture content of the soil. A
deep, narrow foundation, of about 350mm in width and up to 1.50m in depth as shown in figure8.4 could be constructed.
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Fig. 8.4 Deep strip foundation
On a sloppy site it is necessary to step the foundation parallel to the slope of the ground. This is
called a stepped foundation. To prevent differential settlement in a stepped foundation, the height
of the step should not exceed the thickness of the foundation. At each step the higher foundation
should overlap the lower foundation for a distance equal to the thickness of the foundation. An
illustration of a stepped foundation is given in figure 9.5
Fig. 8.5 Stepped foundation
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Test Questions
1. Describe foundation under these headings
a. Shallow foundation b. Deep foundation
2. Sketch 4 types of foundation
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WEEK 9: TYPES OF FOUNDATION CONTINUED
Pad foundation
This type of foundation is used to support and transmit the loads from piers and columns. The
most economic plan shape is a square but if the columns are close to the site boundary, it may be
necessary to use a rectangular plan shape of equivalent area. The reaction of the foundation to
the load and ground pressures is to cup, similar to a saucer, and therefore main steel is required
in both directions. A typical example of a reinforced pad foundation is shown in figure 9.5.
Fig. 9.5 Pad foundation
Raft foundation
The principle of any raft foundation is to spread the load over the entire area of the site. This
method is particularly useful where the column loads are heavy and thus requiring large bases or
where the bearing capacity is low, again resulting in the need for large bases. Raft foundation
can be considered under three headings:
solid slab rafts, beam and slab rafts, and cellular rafts.
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(a) Reinforce concrete solid slab raft foundation (b) Cellular raft foundation
Fig 9.5 Types of raft foundation
Pile Foundation
Pile foundation is used to transfer heavy load to a soil layer of adequate strength located far
below the ground surface that it will be uneconomical to carry out excavation to reach such a
depth. This is used where the soil condition is poor close to the earth surface. Pile foundations
could be made using concrete, steel or timber. The concrete could be precast or cast insitu.
Piles are classified by their method of construction into
Bored or Replacement Piles which are concrete cores poured into holes in the ground at
measured intervals.
Driven or Displacement Piles which are driven into the ground at spaced intervals.
By the way they carry their loads pile foundations are classified into two types. These are End bearing pile, and Friction pile
(a) End bearing piles are those piles that are driven down to soil layer of adequate strength in
such a way that the end of the piles actually bear on this particular soil layer.
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(b) Friction piles are used in situations where the soil layer of adequate strength is located far
below the ground surface such that it becomes uneconomical to produce piles that will go
to such a depth. This type of piles carries their load by the friction that exists between the
shaft of the pile and the surrounding soil particles. The surface of the friction piles are
made rough so that the desired frictional force could be produced as the pile is driven intothe ground.
Test Questions
1. Use drawing to describe a pad foundation
2. State the principle behind raft foundation
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WEEK 10: METHODS OF REINFORCEMENT IN SUBSTRUCTURES
(3.10) Methods of Reinforcement in Substructure
Reinforcement is provided in concrete structures to enhance its tensile strength. Therefore in all
structural elements, the reinforcement is provided in the region of the element that will be
subjected to tension. Reinforcement details as provided in some sub-structures are illustrated
below. Substructures include the following:
Foundations Ground beams
Pad foundations: The reinforcement in isolated pad foundation is provided as the bottom of the
foundation slab. This is because the point load coming from the column or pier subject thebottom part of the foundation to tension. The reinforcement detail is as shown in figure 10.1
Fig 10.1 Reinforcement details of some of a pad foundation
Raft foundation: In raft foundation both the top and bottom faces of the slab are subjected to
both tension and compression depending on the position of the columns and other structural
components that are carried by the raft. The reinforcement is therefore provided both at the top
and bottom of the slab as shown in figure 10.2
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Fig 10.2 Reinforcement details for solid slab raft foundation
Ground beams: Ground beams are provided to support the foundation wall in place of a strip
foundation in poor soil conditions. They are reinforced to enhance their resistance to the loads
that might be coming on them from the wall. There are situations where the ground beams form
component parts of some types of raft foundation. Typical reinforcement arrangement in ground
beams is shown as an integral part of a raft foundation in figure 10.3
Fig 10.3 Reinforcement details for ground beams in a raft foundation
Test Questions
1. What is the main function of reinforcement in foundation
2. State 2 characteristic of a ground beam
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WEEK 11: CONSTRUCTION OF FOUNDATIONS
(3.11) Method of Construction of Foundation
Strip Foundation
Reinforced concrete strip foundations are used to support and transmit the loads from heavy
walls. The minimum thickness of a strip foundation is 150 mm. This may be of course, greater
where the projection of the edge of the foundation from the base of the wall is greater than 150
mm. A typical strip foundation is as shown in figure 11.1.
The construction entails first of carrying out the excavation of the foundation trench up to a
depth of at least 1m. This depth is to ensure that the foundation is constructed at a depth where it
will not be affected by the seasonal soil movement that will cause its failure. After the
excavation is concluded the concrete is then placed and compacted in the trench usually in one
single layer.
Fig. 11.1 Strip foundation
If the nature of the soil will be such that a wide strip foundation will be used, the reinforcement
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is placed at the bottom of the exaction and the necessary concrete cover is ensured by the use of
spacers placed below the reinforcement before the concrete is poured. This is as shown in figure
11.2
Fig. 11.2 Wide strip foundation
Pad foundation
The construction of the pad foundation entails the excavation of the foundation pit to the desired
depth. The bottom of the excavation is overlaid with a weak concrete referred to as blinding. The
reinforcement which is placed in both directions is usually tied in a basket form and then placed
inside the pit with the spacers to give the necessary concrete cover to the reinforcement. The
column starter bars are cast together with the foundation. The concrete of the desired quality isthen poured into the pit to form the foundation. A reinforced concrete pad foundation is shown in
figure 11.3
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Fig. 11.3 Pad foundation
Raft foundation
Because the raft foundation covers the whole area under the building, the excavation has to be
carried out to the desired depth over the whole area the building has to cover. A weak concrete is
placed over the whole area which acts as blinding. The reinforcement is placed with the spacers
to give the desired concrete cover. The reinforcement is placed in both direction and in both
faces. The concrete is then poured and compacted to form the foundation. It might also be
necessary to cast the column starter bars, if necessary. The construction is as shown in figure
11.3.
(b) Reinforce concrete solid slab raft foundation (b) Cellular raft foundation
Fig. 11.3 Types of raft foundation
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Pile Foundation
Pile foundations are constructed either by being driven into the ground by pile drivers or the
ground is bored, the reinforcement is placed and concrete pored and vibrated to form the pile
foundation. In the first case it is called driven pile. The second type is referred to as replacement
pile.
Test Questions
1. Describe a method used in carrying out strip foundation
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WEEK 12: DAMP PROOFING
(4.1) Rising Damp and Seepage of Ground Water in Building
The foundation of the building and the foundation walls are usually in direct contact with the
sub-soil. The ground water level rises and drops depending on the season. This ground water
rises through the fabric of the walling materials and passes through to the superstructure. This
rising damp has the adverse effect of damaging fittings and finishes applied to the building. For
this reason precaution should be taken to prevent this dampness from rising.
The process of preventing the passage of moisture to the interior of a building through the walls,
floors, etc. is referred to as damp proofing. Damp proofing is achieved by the use of damp proof
course (DPC) and damp proof membrane (DPM). While the damp proof membrane (DPM) isdefined as an impervious material placed horizontally at the floor level to prevent moisture
penetration into the interior of the building.
(4.2) Damp Poof Course (DPC) and Damp Proof Membrane (DPM)Damp proof course (D.P.C) simply means an impervious material used to prevent the vertical
rise of moisture through the wall into the interior of the building. The primary function of any
damp-proof course (dpc) or damp membrane (dpm) is to provide an impermeable barrier to the
passage of moisture. However, D.P.C can be used in: Reveals of doors and widows opening Retaining walls Basement walls enclosing laundry
The three basic purposes for which damp-proof courses are used is to:-
Resist moisture penetration from below (rising damp)
Resist moisture penetration from above Resist moisture penetration from horizontal entry
(4.3) Functions of Damp Proof Courses prevents capillary action of water to the super structure of the building. prevents the furniture and insulator of the building from moisture. provides a good barrier to the passage of water from the ground into the structure.
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accommodate pipe, insulator and other electrical fitting of the building in terms of concrete
(D.P.C)
should be capable of adequate resisting any attack by sulphates or any other deleterious
matter present in the subsoil.
The movement of water or moisture into the building is most times upward through the
foundation of wall from the ground.
Paint laid (D.P.C) should be protected on both sides with bitumen to prevent corrosion of the
laid, as it is in contact with cement mortar.
Care should be taken to ensure a good bonding between slate or brick and the mortar.
The diagram above shows the rise of moisture through material to wall above D. P. C too closeto the ground.
Damp proof membrane (DPM) should be impermeable to water either in liquid or vapour from
the ground. It should be rough enough to withstand possible damage during the laying of screeds,
concrete or floor finishes. It may also be sand witched in or under the concrete slab. Being
impermeable to water, the membrane will delay the drying out of wet concrete to the ground, if it
is under the concrete or screed or it is on top of the concrete. Typical details of the procedure
used in laying DPC and DPM are shown in figure 12.1
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(a) DPM laid below the floor slab (b) DPM laid above the floor slab
Fig. 12.1 Damp proof course (DPC) & damp proof membrane
Test Questions
1. Discuss the importance of damp proofing
2. State 3 basic purposes for which damp proofing is provided in a foundation
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WEEK 13 MATERIALS USED FOR DAMP PROOF COURSE
(4.6) Materials Used for Damp Proof Course
Obviously some material must be built into the brick work and ground to prevent any water
being drawn up above a level just above ground. The most convenient way of doing this is to
build into horizontal or vertical joint some material which is non-absorbent or resistant to water
and which is continuous. The materials most commonly used for this are:
Bitumen impregnated felt
Asphalt Hard soil
Bituminous
Lead / Aluminum coreA sheet of copper Fairly firm soil
Polythene sheet
Metal sheet
concrete cement Lose soil
Properties of Damp Proof Course Flexibility Impervious Rigidity Durability
Damp proof course maybe horizontal or vertical placed either below the ground level or just
above the ground level is in order prevent water raising up the wall of the building. These below
ground level are provided with the lowest floor in a building.
These consist of both horizontal and vertical D. P. C must be placed at least 150mm above the
ground level and the vertical D.P.C must connect the two D.P.C form a completion barrier to
moisture. Every wall in a building should have a (D. P. C) which is:
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At least 150mm and above ground level
Above the surface of any oversite concrete
Below the surface member of the timber floor
Moreover the wall should be kept about 25mm away from asphalt and each course flushed up
solidly. The asphalt which is laid on the floor slab should also have a protective screed on top to
prevent any damage by people walking over it. Therefore, reinforcement is to be placed on it or
petrol and oil being spilt from machinery.
Precaution to Be Taken When Laying DPC Always keep mortar bed even and ensure that there are no Unroll bitumen material carefully; especially in cool weather as coldness tend to make them
brittle and liable to crack badly.
Bed slates and bricks carefully to ensure that there are no air puddles beneath them.
Procedure for Placing DPC
The D. P. C is placed horizontally below the ground level to prevent water up the wall. The D. P.
C below ground level is provided where the floor in a building is below the ground level and will
consist of both horizontal and vertical DPC the lower DPC is placed below the floor level and an
upper DPC is placed about 150mm above the ground level. The vertical DPC is connected to the
two to form a complete barrier to the moisture rising up to the structure.
As an impermeable membrane, the DPC prevents termites from penetrating through into the
building. This is because it is a hard surface through which termite cannot penetrate.
D. P. C will not allow any under ground tree to penetrate through the ground to the floor.
Test Question1. State the materials for damp proofing2. Briefly describe various materials for damp proofing on different types of soil
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WEEK 14: BASEMENT TANKING
(4.4) Tanking in Basement Work
Waterproofing presents a great problem in basement construction. It is required that such walls
be constructed so that they will not transmit moisture from the ground to the inside of the
building or to any material used in the construction that would be adversely affected by moisture.
A basement can be waterproofed by any of the following basic methods
Monolithic structures Drained cavities Membranes (of which asphalt tanking is a detailed example)
Asphalt TankingAsphalt is a natural or manufactured mixture of bitumen with a substantial proportion of inert
mineral matter. When heated, asphalt becomes plastic and can be moulded by hand pressure into
any shape. Bitumen has both waterproofing and adhesive properties.
The basic principle of asphalt tanking is to provide a continuous waterproofing membrane to the
base and walls of the basement. Continuity between the vertical and horizontal membranes is of
utmost importance, and since asphalt sets rapidly once removed from the heat source used tomelt the blocks it is applied in layers over small areas. Joints in successive coats should be
staggered by at least 150 mm in horizontal work and at least 75 mm in vertical work.
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(a) Externally applied mastic asphalt tanking
(b) Internally applied mastic asphalt tanking
Fig 14.1 Basement tanking in mastic asphalt
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Test Questions
1. List three basic methods of tanking
2. Describe Asphalt taking
3. Draw an basement tanking using mastic asphalt
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WEEK 15: HARDCORE
(4.7) Hardcore Layer
This is made up of material such as broken stones, rocks and various laterites used to satisfy and
level the uppermost surface of a building area before the ground floor slab is cast upon it.
Functions of Hardcore Provides support to the floor slab Reduces the amount of moisture penetration into the building Used in determining different floor levels in a building wit various floor levels (e.g. dinning
area may be higher than sitting area (living room).
Used for filling in void before construction. Hardcore is important in the construction of solid
ground floor.
Used in determining the different levels in a building, in reduced level excavation. Provides an even level before slab is cast. Helps in reducing undergrowth in penetrating into the floor slab and subsequently into the
building.
Helps to increase the strength level of a building.
Materials Used for Hardcore
The following materials could be used as hardcore
Broken bricks Demolition wastes Broken stones Compacted lateritic soil
(4.8) Blinding
A blinding layer 50 to 75mm thick of weak concrete or coarse sand should be placed under all
reinforced concrete foundations. The function of the blinding are to fill in any weak pockets
encountered during excavations and to provide a true level surface from which the reinforcement
can be positioned. If formwork is required for the foundation some contractors prefer to lay the
blinding before assembling the frame work; the alternative is to place the blinding within the
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frame work and allow this set before positioning the reinforcement and placing the concrete.
Also blinding should be placed on top of the hardcore before the casting of the oversite concrete.
This is to safeguard against the mixture of water, fine aggregates and cement from seeping
through the large voids present in the hardcore layer. It also prevents the rough surface of thehardcore layer from puncturing the damp proof membrane that may placed on it before the
casting of the floor slab.
(4.9) Termite Treatment
Termites present a danger to buildings because they eat the cellulose in the timber in buildingswhere they can not be seen. To remove the danger, the termite nests must be dug out and thecontent destroyed. Anti-termite treatment therefore aims to eradicate termites and the consequent
hazard they pose to the building and its components.
The ground around a termite nest is usually treated with toxic chemicals. The chemicals should
be mixed in open air to avoid its health risk to the workers.
Test Questions
1. Define hard core and state site functions
2. State 4 type of materials that can be used for tanking3. Explain the importance of anti termite treatment