General

Concepts of building construction

Introduction

Building construction is an ancient human activity. It began with the purely functional need of a controlled Human being and their activities are at the mercy of environment to moderate the effect of climate (Awaritefe 2007). Constructed shelters (buildings) were one means by which human beings were able to adapt themselves to wide variety of seasons and become a global species, involved in the promotion of the quality of the environment and health, thus, improving the quality of life of a community through an organized building sanitation

The word building is both in noun and verb; as a noun, building is a man made structure that has a roof and walls, and stands more or less permanently in one place. As a verb building is the act of construction.

Idibia (2009), defined ‘’building’’ as any physical structure that is erected on or in the land to provide shelter and protect man from the adverse effect of the weather such as rain, wind, snow, heat, temperature etc.

According to Delta State Building Adoptive Bye Laws No 14 Cap. 21, building include structure or erection of any kind or nature whatever and any addition or alternative of existing building. In actual sense building means ‘’that which is built, a structure edifice ‘’ Building is actually a roof and wall structure. Construction in a very general term is the art and science to form material or immaterial objects, system etc. It is the process of putting different material together to produce something else.

It is pertinent to intermarry the two words and come up with a concise definition of building construction.

Building construction

Is the process of putting structures together for the purpose of human settlement amongst others. Moreso, building construction is the techniques and industry involved in the assembly and erection of structures, primarily used to provide shelter.

In a nutshell, building construction is the construction of building by builders.

Who is a builder?

A builder is any person who is actively engaged upon the construction or alteration of any building.

Categories of building construction

S/N	Types of Building Construction	Examples
1	Residential buildings construction	Houses, hotels, motels, hostels etc.
2	Industrial buildings construction	Factories, breweries, mill etc
3	Commercial buildings construction	Banks, stores, markets etc.
4	Institutional buildings construction	Hospitals, schools, prisons etc
5	Heavy civil engineering buildings construction	Airport, stadium, etc.

Note: different type of buildings can serve for a particular purpose or vice-versa and is termed mixed occupancy.

What is building sanitation?

Building sanitation is the control of those factors in the building, which exercise or may exercise deleterious effects on the health and general well being of its occupants. It entails, the proper construction of buildings, adequate provision of sanitary facilities and hygienic usage by the occupants. A sanitary building provides a sanitary environment, which is safe and conducive for physical, mental and emotional health of its occupants in order to achieve maximum state of health. Whereas the art and science of bringing about healthful and hygienic conditions is termed sanitation (Webster Neworld Dictionary). Oxford Advance Learner Dictionary defined sanitation as the arrangements to protect public health.

Aims and objectives of building construction/sanitation

To Choose a suitable building site locations that complies with existing regulations of site selections.
To approve building plans which meet the standard of fitness, for human habitation.
To enforce relevant statutory regulations, that relates to the construction of new buildings.
To ensure the maintenance of pleasant environmental conditions, of a building and its surroundings.
To carry out inspection in order to detect unsatisfactory conditions in building environment and decide how to abate them.
To prevent the spread of diseases arising from insanitary environmental conditions.

Categories of workers involved in building construction/sanitation

Land surveyor: Is somebody who carries out measurement and mapping of the surrounding environment using mathematics, specialized technology and equipment. A surveyor measures just about anything on the land, in the sky or on the ocean bed.
Soil investigation experts: Are experts involved in soil testing to assess the suitability of the soil for construction project, with vital data for informed decision making and planning.
Builders: Those who are actively engaged in building construction or alteration. e.g. brick layers.
Environmental health officers: Are professionals who carryout measures to protect public health which includes enforcement of legislation relating to environmental health and providing support to minimize health safety hazard.
Civil engineers: These are professional in engineering discipline who deals with the designing, construction and maintenance of the physical, and naturally built environment such as works like stadium, airport and buildings.
Architects: Are those professionals, involved in the process and product of planning, designing and constructing of building and other physical structures.
Town planners: They are skilled personnel’s involved in the comprehensive planning of the physical and social development of a town.

Roles of environmental health officers in building sanitation/construction

The duties of an Environmental Health Officer in relation to building include these and many others:

He carries out site investigation to ensure that the site meet with the essential health facilities required of a site, to promote health and well-being.
He enforces the total compliance of existing regulations/plan.
He is involved in the vetting and approval of the building plan to ensure that such plan complies with all the sanitary provision of both public health law and building bye-laws.
He issues abatement notice to building owners, if he notices the existing of any nuisance at the building site.
He inspects and certifies the standard of sanitary facilities in the building before it can be occupied.
He carries out inspection of substandard housing conditions

What is a house?

A house is a “residential environment” which is defined by World Health Organisation ( WHO) Expert group; as the physical structures that man uses for shelter, immediate surroundings, and the related community services and facilities needed for the physical, mental and social well-being of an individual and family. A house is a building constructed to accommodate man and his personal effects/belongings. And Olorunda (2007), defined a house as “a building or premises built within the laid down building regulations to occupy person or persons and their personal effects, possessing all sanitary conveniences, providing comfort shelter, privacy, protecting and elongating and preventing diseases associated with housing”. From the above definition, it is clear that a house is a man-made physical structure which serves as shelter either in the home, business, or work places and also encompasses all the necessary facilities and equipment required for a comfortable stay. A house accommodates a household. That is, flats or houses for human settlement.

“Housing” has become part of the concept of “human settlement” which is referred to as “all places in which a group of people reside and pursue their life goals. The size of the settlement may vary from a single family to millions of people.

A slum: is defined as a group of building or areas characterized by overcrowding, deterioration, insanitary conditions or absence of facilities or amenities which because of these conditions or any of them, endangers the health, safety or morals of the inhabitants or the community (UNESCO).

Purpose of building/housing

According to Vidya (2003) an ideal housing /building shall be constructed, maintained and occupied in a manner as to meet the following needs:

Fundamental psychological needs:

Shelter: To provide sanitary shelter for its occupants

Family life: To provide adequate space for family life and related activities, viz: sleeping and relaxation, food preparation and storage and good excretory disposal system.
To provide access to community facilities and services such as school, places of worship, health services etc.
Economic stability: To promote investment of personal savings for the well-being of the family

Fundamental physiological needs:

To ensure good ventilation.
To ensure proper lightening system
To provide space for children to play.
To protect against excessive noise and heat.
To ensure adequate portable water supply.
Good waste disposal system.

To protect against communicable diseases:

It should be designed construct maintained and used in a manner such as to prevent communicable disease.

It should be designed, constructed, maintained and used in a manner such as to prevent communicable diseases.
It should encourage personal and community development, social relationships, reflect a regard for ecological principles, and by this means promotes mental health.

Characteristics of an ideal house/building for human habitation

An ideal building should possess the following characteristic;

Must be built according to approved building plans.
Must be well sited and made permanent in a good soil free from pollution and away from highway.
Impervious and durable materials should be used for the building.
A strong cement plastered wall with water proof roof
A safe portable and convenient water supply
A proper drainage system
Adequate sanitary conveniences such as bathroom, toilets, urinal.
A damp proof course and a smooth floor
Good natural and artificial lighting
Adequate space for recreational activities and relaxations
Separate room for living and sleeping with standard size measurements
Satisfactory provision for storing refuse.
They meet 100% of sanitary/public health requirement.

Ideal building possesses 100% of sanitary and public health requirements. The provision of the above requirements in a building will contribute immensely to the health and well-being of man.

Types and characteristics of buildings or housing

There are basically four categories of housing or building conditions used by man, they include:

Type A buildings
Type B buildings
Type C buildings
Type D buildings

Characteristics of type A buildings

Must be built according to approved building plans.
Must be well sited and made permanent in a good soil free from pollution and away from highway.
Impervious and durable materials should be used for the building.
A strong cement plastered wall with water proof roof
A safe portable and convenient water supply
A proper drainage system
Adequate sanitary conveniences such as bathroom, toilets, urinal.
A damp proof course and a smooth floor
Good natural and artificial lighting
Adequate space for recreational activities and relaxations
Separate room for living and sleeping with standard size measurements
Satisfactory provision for storing refuse.
They meet 100% of sanitary/public health requirements.

Characteristics of type B buildings

It is built according to approved building plan.
It is sited in a good soil free from pollution
It constructed with strong impervious materials
It has a strong damp proof course.
The walls of the rooms are strong and made smooth
The floors are well constructed and made smooth
It has a well constructed drainage system.
It possesses 75% of all the requirement of type A building
It requires some little amendments and provisions to make them meet with the standard of type A.

Characteristics of type C buildings

These are buildings constructed with mild materials i.e. mud blocks or slightly strong brick materials. Site selection is not necessarily taken cognizance of. All sanitary and health requirement to fulfil a healthy living are almost absent or partially provided. There may be presence of dilapidated walls.

Characteristics of type D buildings

It does not require a building plan.
It is cheap and simple to operate.
These categories of buildings are constructed with wood, bamboo, raffia or zinc.
It is expected to serve for a temporary use as the materials used in their construction cannot withstand a longer period (e.g. bamboo hut and grass hut).
It is deprived of all forms of sanitary conveniences
It is liable to cause an epidemic and can easily be destroyed by fire and dangerous to live in during rainy season.

Building and health

The relationship between building and health is multi-faceted. An ideal building needs to have sound structure to be free from hazards and provides adequate facilities for sleeping and relaxation, privacy and quietness, and to provide the facility for social exchange with friends and others. It is an established fact that, buildings built without compliance to statutory regulations that relates to building construction and sanitation will expose its occupants to the following hazards.

Physical
Biological
Psychological hazards.

Physical hazards

A high proportion of accidents, heat and cold occur inside the building as a result of poor designs and maintenance and they are particular concern for children and the elderly. These can bring about injuries, sickness and death from fall, burns, electric shocks and also atmospheric pollution from smoky wood fires, excessive noise, poor lighting and overcrowding.

Biological hazards

The risk of the transmission of communicable disease has link to buildings. Damp and mould have repeatedly been linked to a number of health outcomes, including respiratory symptoms, nausea and vomiting and general ill-health. Poisoning from carbon monoxide occurs as a result of poorly ventilated and maintained combustion sources (gas boilers, fire, etc.) can cause respiratory discomfort. Unwholesome water supply and poor storage of food can increase the spread of gastrointestinal infections.

Psychological hazards

A psychological hazard is a potentially very important factor that has bearing on the mental well-being of the dwellers in a building. These factors are; inadequate privacy due to overcrowding, lack of facilities for personal cleanliness and for performing household duties with undue fatigue.

Building regulations relating to environmental health

National building code adopted by Federal Government Executive Council in August/September 2006
Building Adoptive Bye-Laws Order (1960).
Public Health Laws of Nigeria as applicable to states of the federation.
National Guide on Environmental Health Practice.
Environmental Health Officers Registration Council of Nigeria Act 11 of 2002.

Building plan

A building plan is a drawing, which shows the features of the proposed building and its related facilities made to scale on a paper. A building plan must be approved by relevant government authorities before the commencement of the building process.

Features of a building plan

It contain detail of the elevation front sides and rears
It shows the dimension of rooms, windows, doors, bathroom, toilets etc
It must show the area built upon
It must show the distance between the proposed building and existing building
It has space for signature and stamp of approving authorities.

Importance of building plan

It gives legitimacy to the owner of the building.
It provide guides during construction

iii. It can be used as collateral

It provides structural details during constructions

Aspects of the building plan to be examined by the EHO before approved.

The areas to be examined in a building plan by the health officer before approved includes:

Size of the plot
Size and area of the building that is going to the plot according to appropriate building regulations.
Rooms dimensions and sizes in compliance with the building regulations.
Positions in windows and doors for proper lightening and ventilation.
Availability adequate and dimensions sanitary facilities within the structure i.e toilet bathroom kitchens, store e.t.c. The position in relation to the living rooms and bedrooms and the dimensions of these facilities should be adequately checked.
Check total area covered by the building to ensure that the plot is not over-built, in accordance with existing laws.
Check the necessary allowance maintained between the proposed building line.
The environmental officer may recommend or approve the plan if satisfied that the plan meets appropriate requirement of the relevant building regulations.

Building site

A building site also referred to as plot of land is the location at which the proposed structure (building) is to be constructed or situated. The site of a proposed building determines to a large extent the general well- being of the occupants of the building erected on it.

Factors to be considered during site investigation/selection

The factors to be considered during site investigation for building purpose are as follows;

Nature of the site
Type of soil
Proximity of site to other adjoining properties
Topography
Accessibility
Location of site
Climate condition
Availability of water and electricity
Size of the plot
Direction of winds.
Drainage system

Qualities of an ideal building site

An ideal building site must possess the following qualities;

The site should be naturally drained.
It should not be liable to high level of pollution
It should not be low-lying, depression that is liable to flooding or water logged. Thus, should be an up land.
It should not be a made-up soil or not properly consolidation soil.
It should not be exposed to wind/storm
It should be accessible to other basic amenities such as school, market, hospitals, water road telephone service, electricity etc.
It should not be infected with insect or termites.

Site activities that precede the actual building construction work

In preparing the site for the building construction work to commence the following activities must take place, viz;

Clearing of site either manually or mechanically
Filling and levelling of undulated site with earth or other suitable materials.

iii. Provision of drains in site that is not naturally drained.

Planting of quick growing tress in site exposed to wind or water logged etc.
Access road to allow easy conveyance of materials to site.
Control of insect or termite infestation if any.

Measures to control insect (termite) infestation in site/building

The following measures should be employed to remedy insects’ infestation in a building or site:

The site should be treated with Basudin 106 before erecting the building.
If it is a building, the corners should be excavated round and sprayed with Basudin 106 or any chemical before it is covered with earth. Same should be done to foundation trench of a proposed building before the concrete foundation is laid.

Necessary facilities needed in a building site

Temporary material store: Is a place built for storage of materials and work tool, to be used during the construction of the building. It can be built with corrugated iron sheet etc. and might be demolished on completion of the building.
Temporary site office: Is built for worker relaxation in case of intense sun, rain, record keeping or even to eat their food. It is usually provided in a large construction site.
Cloak room: A place built for workers to change their clothes
Shallow trench latrine: if need be.
Well or borehole water: Is needed for workers to get water for use at any time of the work.
Light: Is needed for some of the construction work such as welding, wood work etc.

Building construction materials

A building materials means a material used to form the structural elements or part of building structures. The building materials that are commonly of usage are as follows:

Cement: This is a building material that is manufactured from clay, chalk and shale. It is normally mixed with little quantity of water to bind particles of sands in the production of either block or cement mortars.
Cement mortar: This is a cement paste made from the mixture of one part of cement to two parts of sand (1:2) mixed with water for holding bricks and blocks together or for plastering the surface of walls and floor.
Sand: Is a very fine particle of crushed rock. It is used with cement in the manufacturing of blocks concrete or cements mortar. Good sand should not contain clay, roots or other material.
Gravel: This is one of the commonest building materials that is frequently used in foundation and concrete work. It is obtained naturally from the soil and used as coarse aggregates in making various types of concrete work such as foundations, beams, lintels, pillar, of buildings.
Concrete: Is manufactured from the mixture of cement, sand, and gravel with sufficient water in varied proportions. It is used in making foundations, beams, lintels, pillar of building.

The proportions by which concretes are manufactured are as follows;

One part cement, three parts of sand and six parts of coarse aggregates [1:3:6] for foundation concrete.
One part of cement, two parts of sand and four parts of coarse aggregates [1:2:4] for reinforced concrete work.
One part of cement, four parts of sand and eight parts of coarse aggregates [1:4:8] for rough-cast concrete.
Cement block: It is a solid piece of building material with flat surfaces on each side made from a mixture of clean sand, cement and water. It is made mechanically or manually with moulds. Blocks are made of different sizes such as 4 inches, 5 inches 6 inches or 9 inches. It could be hollow or solid in nature.
Literate: Are materials needed to raise a very low site to a desirable height before building is erected. It is also used in filling up the floor of a building before the concrete floor is cast.
Woods: There are two types of wood, soft and hard woods. Softwoods are used in erecting foundation profiles, casting of concrete beams, lintels etc. whereas;

Hard woods are used in making wooden windows and doors, and also in the structural framework of roof (trusses).

Creosote: This is a wood preservative used in making timber resistance to wet and dry rot. It is also used in repelling destructive pest (insects) of timber.
Roofing sheet: These are broad thin piece of materials made of corrugated iron, asbestos, aluminium etc. used as ceiling or roofing buildings, it could be long span or short span.
Bricks: This is a walling material made up of clay soil into a small rectangular shape. It is mechanically or manually made with the aid of a mould. It may be burnt or un-burnt.

Quality of a good brick

A good brick should emit a metallic sound when two are strucked together.
It should be uniform in size
Should be strong and not easily broken
Should have sharp edge
Should not absorb more than 10% of their weight of water if soaked for 24 hours
Nails: These are steel materials with a flat head used to hold things (wood, roofing sheets) together during construction. There are of different size ranging from 75mm, 160mm, and 150mm etc.

Building tools

The following tools are required during building construction, viz;

(1) hand towel (2) Tape (3) Plumb (4) Theodolite (5) Wooden pegs (6) Shovel

(7) Cutlass (8) Head-pan (9) Builder square (10) Hammer (11) A ball of string (12) nail, etc.

What is setting out

Setting out is the process of developing the physical positions of corners and walls of a building and it’s done by transferring dimensions from the layout plan to the ground. It is done when building a new house or when renovating or extension. It is important to ensure that the big rectangle (external walls) is set in a horizontal level.

The main reason for setting-out a building is to establish the position of the trench and wall of the house as well as the position of corners and rooms.

Methods of setting-out a building on the site

The following methods are used in setting out a building either manually for simple building or mechanically (instrument) for simple and complex buildings viz;

(i.) 3,4,5, methods

(ii.) Building square methods

(iii.) Theodolite method

The 3, 4, 5 method

If the building is rectangular, the right angles are set off from the front line by using 3,4,5 methods

The procedure for applying the 3, 4, 5 methods are as follows:

Mark out the building line from the road or stretch a line along an existing building to the proposed site. The building line is then represented with a line known as the ranging line.
Mark out the overall length of the building by driving pegs of A, B, C & D.
Mark a distance of 3m along the ranging line starting from A, and, mark the line to point B.
Mark a distance of 4m along the second line starting from corner A to C.
Mark a line with a distance of 5m from line A to C. let the line at point B meet C.
Taut the rope of the line. The measuring is best done with two persons one at the ends of each line.
Set out the opposite side in the same way. If the setting out has been done accurately, the length of the back line (i.e. CD) should be equal to that of the front line.
Make a further check by measuring the diagonal which must be equal.
Once the position of the corners and the distances between them are determined, the position of the foundations and walls and thickness must be marked.

Building square method

This method is a good example of instrumental method of setting out a building. It involves the use of an instrument called building square to measure the vertical or horizontal angles of an established corner pegs and erected profile.

With the aid of this instrument the builder ensures that the foundation trench to be excavated is balanced and accurate to the roofing level. The ordinary builder mostly use of this instrument.

Theodolite method

This method involves the use of a telescopic, an instrument called theodolite to survey and measure the angles on the profile either vertically or horizontally. It is used to establish the correct and balanced position of the partition wall which are marked and pegged to the ground to indicate the line of excavation of the foundation trenches. Construction companies mostly make use of this instrument.

Building components

These are the essential parts of a building. Building components includes

Excavation
Foundation
Damp proof course (D.P.C.)
Floor
Walls
Ceiling
Roof
Door
Windows etc.

Excavation

Excavation is usually next site operation that follows setting out and profiling of the building process. The type of excavation to be used depends on the type of foundation to be laid, such as excavation on trenches where the foundation are to come only and excavation of the whole area where the building will rest on otherwise referred to as bulk excavation (raft foundation).

Excavation may be done manually using shovel, cutlass, digger and spade, especially for simple domestic buildings or mechanically using excavation machine (excavator) such as bulldozer, scraper, mechanical shovel, scraper etc) may be employed for longer excavation needed for buildings.

Foundation

This is the initial part of a building that is below the ground surface on which the whole building structure (weight) rest. It is the concrete part (base) of the structure that bears the weight of the building and transfer it into the soil.

A foundation has two compound, viz:

Natural (soil) foundation: It is the base of the trench (sub soil) upon which the building weight rest.
Artificial (concrete) foundation: It is the concrete part of the structure at the base, which transmit the building load to the natural foundation. Example includes; raft foundation, stepped foundation etc.

The materials to be used in foundation laying should be sound and accurate to withstand the load (dead load, imposed load, and wind load) that would be excreted, on it. To form foundation concrete, the mixing proportion of 1:3:6 or 1: 4: 8 should be used i.e. one part cement, three parts sand and six parts gravel.

The foundation concrete is laid over the excavated trench at a thickness of 15cm for bungalows and 23cm for other types of building where the soil is normal, and tapped evenly for adequate compactment. Thereafter, the foundation concrete until it gets to D.O.P level.

Categories of foundation

Foundation could be deep or shallow.

Shallow foundation: Is often called footing. It is shallow when the load bearing layer is in shallow location, usually a meter or so into the soil. Strip. Strip, stepped or raft foundation can be in shallow form.
Deep foundation: As the name connotes, it is dug deeper. It is a foundation where the load bearing capacity of the soil, is deeper location or where the load of the building are two heavy e.g. pile and pad foundation

Characteristic of a good foundation

A good foundation is one that:

Has the ability to carry the weight of the building.
Should not be destroyable by roots of big trees
Should not be affected by water.
Should withstand the underground movement of the subsoil
Should provide an even or levelled platform for building structure.

Types of foundation

The common types of foundation employed in building construction operation are:

Strip foundation – This is the most common types of foundation, used mainly in non-water logged areas and strong soil. The strip foundation for a bungalow will be 450mm wide and at least 200mm deep. For state buildings 600mm wide and 200mm deep in this method, concrete (6-18 inches) thick is poured in a built excavated trench and tapped. Thereafter, block is laid at the centre of the foundation all round the trenches
Raft foundation (reinforced concrete): In this types of foundation reinforce concrete is poured from base of soil to ground floor level or German floor lever, under the whole area of the building. It is mostly used in sandy or loose soil water-logged area and made-up soil but with building of less storeys. It is usually 600mm thick.
Pad and pile foundation: These are reinforced concrete pillars that are casted in holes bored into the ground or precast pillars driven into the ground reach a stronger strata to carry a scab at the top of the ground. The holes are mechanically dug with an auger to about 250mm – 350mm in diameter. It is mostly used in water-logged area, clay or loamy soils.

Various types of soil that determines choice of foundation

There are different types of soil, which to a great extent determines the type and size of foundation to be laid on it. Amongst are:

Rock: A hard and durable type of soil which is suitable for stripped foundation. It is the best soil to build upon because it has high load capacity.
Cohesive or clay soil: Is a type of in which the particles become sticky when wet and hold together when dried good examples of cohesive soil are silt and clay. They retain quite a lot of water thus remaining damp for a long period. They may be suitable for stripped, piled and pad, raft foundations.
Non-cohesive or sandy soil: Types of soil in this category are gravel and sand they allow water to flow through them because of their large particle size. They are suitable for stripped and raft foundation.
Loamy soil: It lacks the load bearing capacity, which is required of a good subsoil. They are suitable for pad and piled foundations
Made-up soil: This soil results from the reclamation of marshy grounds or low lands, which are composed of fill materials. The soils are soft and as such cannot carry heavy loads (made-up ground must be allowed a period of time, about 10- 20 years to consolidate before erecting any building project on it. Site engineer decides on the types of foundation to be used in mad-up grounds. They are suitable for raft foundation, pad and pile foundation.

Damp-proof course (D.P.C)

DPC is a barrier of impervious materials (concrete, cement mortar or tiles) placed at horizontal position of the wall above ground level or vertical position of the wall that is in contact with the adjacent soil to prevent moisture from passing through the walls into interior spaces Its main function is to prevent damp penetration into the building. In the process of damp proofing, the mortar is mixed in the ratio of one part cement to one part sand and water. (1:1 ratio) respectively and spread to form an impervious layer of three to six inches thickness before the walls of the building are erected. It is laid after the foundation wall of the entire building. The installation of DPC is a key stage of the building process and one which really needs to be.

There are two main types of damp proof course, viz;

Vertical Damp-proof course materials includes; mortars, titles etc.
Horizontal Damp – proof course materials includes; mortar polymer modified bitumen etc.

Note: The types of damp-proof course to be used in a particular building depends on the nature and type of soil of the site

Importance of hard core in damp proofing

Hard core is important is damp proofing because of the following:

It is an impervious material.
It cannot be disintegrated as a result of chemical reacting that takes place due to the process of capillary movement of underground water.

When mixed with cement and sand in the right ratio, it forms a very good stratum of impervious materials that prevent dampness in building.

The process of rising and seepage of underground water

Seepage is a process whereby accumulated/storm water through infiltration reaches the impervious rock (aquifer). That is, the gradual movement or penetration of water through small opening into the soil to form underground water. The underground water rises through a capillary movement upward to reach the surface in form of moisture which makes the soil moist (damp). The rising damp sucks into the block or walls and floor of the building gradually to cause dampness which discolours walls and destroys properties and also causes health problems.

Sequel to the above it is pertinent to damp – proof structural work in order to prevent dampness that may result from the upward movement of underground water through a layer of impervious materials (D.P.C) to safe-guard the structure and materials within the structure.

What is dampness?

Dampness in building is one of the most serious defects in building. It is characterized by the growth of greenish or dark grey vegetable matter, rapid deterioration of walls, woods and plaster decay.

Causes of dampness in building

Dampness in building may be due to the following causes;

Capillary or Osmotic actions that are due to absence or insufficient damp-proof course in buildings
Porosity of all material that are due to the use of unsound or substandard materials such as block and cement mortar
Absence of over-hanging cause of roof which allow easy splashing of rain water on the wall surface
Deposition of wet materials such as rubbish or a height above the damp proof course.
Defective roof, rain water pipes or gutters which drip rain water directly into the walls of building
Large trees surrounding building which attracts moisture and reduce the drying effects of the sun and wind (Idibia, 2009).

Remedies of dampness on buildings

Dampness in building may be guarded against through the following ways:

Use of sound damp proof course materials to prevent damp penetration of moisture by capillary or osmotic actions
Use of standard building materials in the construction of external walls to prevent dampness due to porosity of the wall.
Renewal or replacement of defective roofs rainwater gutter and pipes.
The deposition of reduce or latrine against the walls of buildings and surrounding walls should be discontinued.
Cutting down of large trees and packing of residues surrounding building.
Adequate projection of roof eaves to prevent splashing of ram waters on the external walls.

Floor

It is the lower surface of the inside of a building above the foundation wall. It is filled with laterite (soil) which is compacted or allowed to compact to a desirable height. Thereafter stones of varying size referred to as hardcore are arranged on top the compacted soil which is covered and rendered smooth with concrete. Although, many building omits, the hard core and bring the floor to a smooth finish with concrete and cement mortar. The floor is the main building component that bears the weight of the imposed load and should be made with durable materials.

Bonding

Bonding means the way in which blocks/bricks are arranged during wall construction so as to overlap each other. Thus, ensuring maximum strength and stability at the same time avoiding straight joints. It also gives a wall a smooth and alterative surface appearance.

Reasons for bonding

To ensure that there is no straight joints in the wall.
To give the walls a smooth and attractive appearance
To support the needed strength and stability required of a wall.

Walls

After the construction of D.P.C on the foundation, the erection of the wall is commenced. Walls are structural components that form the sides of a building. Building walls are erected on top the foundations (D.P.C), to render support to the ceiling, roofs and upon which windows and doors are fixed. It may be built with mud, blocks, bricks, planks, thatches, bamboos, corrugated iron sheets etc.

Types of walls

The various types of walls in building are:

Retaining walls: These are walls which retain water and are used in septic tanks, swimming pools etc.
Internal/partition walls: These are walls used in the internal partitions of a building. It divides the building into rooms.
External walls: These are walls that form the external body of a building upon which windows and doors are normally fixed.
Load bearing wall: These refers to wall constructed for the purpose of load bearing. Examples are the ground floor walls of a story building which bears the weight of the first floor.

Construction of walls

When erecting walls cement mortar of about 1-3cm thick is spread on top and in between blocks with a trowel. The block are carefully aligned on top the cement mortar leaving a space of about 2cm, which is filled with cement mortar (bonding) between such successive blocks. Subsequent courses, continuous in like manners. In order to ensure that blocks are carefully aligned and stable, a tin rope is tied to both ends of the block row, ensuring that the blocks does not torch / push the rope. Thereafter, a spirit level (plumb) is placed on the top and side of the blocks to confirm the stability. Plumb and square gauge are used to ensure that blocks laid at the corner or ends of walls are at an angle of 90^o.

The space forming the door and windows are left out, which may be fixed with frames during construction or left until later when plastering is carried out. When the erected walls (blocks) progresses to the windows and doors level the lintel will be poured.

Lintel

Lintel is a horizontal reinforced concrete layer across the top of a window and door to support the weight of the building and bridge the gap of openings. Lintels are casted (in-situ) scaffolds planks which are nailed to the blocks/bricks to maintain the correct position and size of the brick/block reinforced with steel which and are poured with concrete and allowed to dry before the planks are removed or dismantled.

The concrete is mixed in the ratio of one part of cement, two parts of sand and four parts of gravel (1:2:4) mixed with water. After the lintel has been formed, erection of walls (blocks) continuous until the required height is attained after which the construction of the roof begins

Windows

These are structures which are fixed in the opening of a wall as means of ventilating and lighting the interior of the building. It may be made of glass, wood, or metal of varied dimension

Types of window

They include the following among many others;

Louvers window: Are windows made of glasses cut into various lengths. They are provided with pairs of metal frames which are screwed into wooden frames, before fixing the glasses.
Sliding windows: Are glass windows fixed into sash. The window slides horizontally or can be slid up and down to open it.
Casement window: Are windows which have two equal apertures that are arranged to provide outward openings. They are usually hung at their sides to the frames.
Fanlight window: Are windows which consist of two parts, with the lower part being greater than the upper part form which the name of the window is derived.

Functions of window

The functions of window include the following:

Windows allow the passage of fresh air and light into the rooms of a building.
It provides occupants with the opportunity of sighting outside the building from the room. The type of window and their positioning in buildings give pleasant appearance.
Windows also provide security to the occupants of the building from the attacks of enemies
It also serves as an escape road on emergency situation

Door

These are movable screens fixes in the entrance part of a building and its living area which permits movement, ventilation and lighting. Doors are usually constructed of metals, wood, glasses etc.

Functions of doors

The functions of doors are

Doors provide access to the building
It admits air and light into the rooms of buildings
It gives attractive appearance to buildings
It ensures security of live and properties when properly locked etc.

Types of door

They includes amongst many other:

Flush door- These are doors which are formed of ply-woods. They have two smooth surfaces, which conceal the internal frame work.
Battened, ledged and braced door – This is constructed of grooved and tongued match boarded, face fixed into a framework of mortise and tenon joint.
Battened and ledged doors: These are doors which consist of boards (battens) which are tongued and grooved into match boarded face and them fixed vertically on to the ledges by means of nails.
Panel door: These are doors framed by joining the member where they intersect. By mortice, tenons, tongued and graves joining. They may be constructed by timber, glass or metals etc. They are named according to the number of panels.

Door sizes and their uses

Basic size height	Width	Use
2 100mm (7ft)	900mm (3ft)	For external doors
2 100mm (7ft)	800mm (2ft-7inches)	For internal doors
2 100mm (7ft)	700mm (2ft-3inches)	For cloak rooms
2 100mm (7ft)	600mm (2ft)	For small cupboard

Ceiling

This is the upper inner surface /part of a building just above the walls before the roof. It is fixed into the roof trusses, after the roofing of the building to prevent excessive heat or cold from the roof. It could be made of glasses, asbestos, ply wood etc. but must be made of insulation materials.

Trusses

This is the structural framework of a roof which supports the roof coverings. It is composed of tie beam, king post, principal rafters, purlins, rafter. It is the upper outer covering of a building that sits on the wall. it main function is to secure maximum protection against prevailing winds intensive heat and sunshine as well as to ensure structural strength, stability and durability and above all give beautiful appearance to the building. It should be sloped to drain off rain water.

Once the wall of a building has attained gable end, the next step is to construct the truss (timber roof). The construction of trusses starts with the framing of wall plate horizontally on top the wall of the building. After which the tie beams are framed to hold the foot of the principal rafter from sagging. The beams runs across the width of the building from one end to the other and may serve as ceiling joint to most buildings.

Next in the order of construction is the king post which is vertically fixed at the lower end of the tie beams and upper end of the ridge. Thereafter, a flapping timber called principal rafter is fixed at the upper ends of the king post and lower ends of the tie beams, this is braced with a strut which is fixed at the upper end of the principal rafter and the lower end to a tie beam to prevent the tie beam from sagging.

Next is the fixing of the ridge (board) which is the horizontal board that runs length wise at the highest point of the roof which holds the upper ends of the common rafters and the lower ends are nailed to the wall plate to provide basis for fixing the purlins- these are horizontal timbers laid length wise across the rafter to provide intermediates support as well as a point for fixing the roof coverings. The final work to complete the roof truss is the facial board which serves as rat proof to the roof. It is mounted with gutter bracket.

After the construction of the truss has been completed the next step is to cover it with corrugated iron sheet, thatches, asbestos etc, this is fastened with a nail, washer and leather to the truss.

Roof/roof covering

It is the upper outer covering of a building constructed either of thatches, plain tiles, pan files, or corrugated iron sheets etc. It is fastened with a nail, washer and leather to the truss.

Roofing sheets are of two categories, viz;

Long-span roofing sheet – As the name connotes, these are long roofing sheets that covers from the ridge end to the Eave (lower) end. e.g Aluminium long span roofing sheets.
Short-span roofing sheet – This is a short roofing cover or sheet. It is nailed in between two purlins. E.g Zinc asbestos roofing sheets e.t.c

Truss/roof terminology

Common rafter: A roofing member, which is bevelled and nailed at the upper end to the ridge board and at the lower end to the wall plate it provide the basis for fixing the purlins.
Gable: The triangle part of the gable end
Gable end: Vertical wall of a building that extends to the ridge.
Eaves: The lower edged of the sloped roof surface, which over hangs the walls.
Truss: A structural framework, which supports the roof covering. It is composed of the tie beam, king post, principal rafters and struts. Its objective is to carry the load of a number of adjacent rafters via the purlins.
Wall plate: A horizontal timber that is laid on top of a wall
The tie beam: A timber on which the foot of the principal rafters are framed or bolted, thus preventing them from sagging
Ridge: The highest line of the roof. Is also called vertex or apex of roof
Purlin: A horizontal timber bid length wise across the rafters. It provides immediate support as well as a point for fixing the roof covering.
King post: A vertical timber of the truss that is fixed at the lower end of the tie beam

.Principal rafter: A slopping timber of the truss. They are fixed at their upper ends, of the king post and their lower ends to the beam
- Ridge board: A horizontal members or board that runs length wise at the highest point of the roof through which the upper ends of the rafter are nailed.

Qualities of a good roof

An ideal roof should posses the following qualities:

Should have the ability to drain off rain and snow
Should not require frequent maintenance during its life time
Should have sufficient strength to support its own weight and that of due to rain and wind pressure
Should be resistant to fire
Should prevent excessive loss and gain of heat.

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