MAINTENANCE TECHNOLOGY...Building maintenance technology essentially deals with the study of the occurrence of building defects and the remedies which such defects would require. The

UNESCO-NIGERIA TECHNICAL &UNESCO-NIGERIA TECHNICAL &

VOCATIONAL EDUCATIONVOCATIONAL EDUCATION

REVITALISATION PROJECT-PHASE IIREVITALISATION PROJECT-PHASE II

YEAR II- SEYEAR II- SE MESTER IIMESTER II

THEORY/PRACTICALTHEORY/PRACTICALVersion 1: December 2008Version 1: December 2008

NATIONAL DIPLOMA INNATIONAL DIPLOMA IN

BUILDING TECHNOLOGYBUILDING TECHNOLOGY

MAINTENANCE TECHNOLOGYMAINTENANCE TECHNOLOGY

COURSE CODE: BLD208COURSE CODE: BLD208

TABLETABLE OF CONTENTS OF CONTENTS

WEEK WEEK 1 1 BUILDING BUILDING MAINTENANCE MAINTENANCE TERMINOLOGIESTERMINOLOGIES

1.1 Building Maintenance Terms

1.1 Types of Maintenance

1.2 Nature of Maintenance

1.2 Maintenance NeedsWEEK WEEK 2 2 CAUSES CAUSES AND AND AGENTS AGENTS OF OF DETERIORATION DETERIORATION OF OF BUILDINGSBUILDINGS

1.2 Common Factors of Deterioration

1.3 Causes and Agents of deterioration

WEEK WEEK 3 3 DIAGNOSIS DIAGNOSIS AND AND INVESTIGATIONINVESTIGATION

1.1 Diagnosis Terminology

1.2 Need for Building Diagnosis

1.3 Process of Investigation.

1.2 Remedial Measures Recommendation.

WEEK WEEK 4 4 FOUNDATIONS FOUNDATIONS DEFECTSDEFECTS

2.1 Causes of Foundation Defects.

WEEK WEEK 5 5 FOUDATIONS FOUDATIONS (ASSESSMENT (ASSESSMENT AND AND REMEDIAL REMEDIAL MEASURES)MEASURES)

2.3 Assessment of Foundation Defects.

2.3 Procedure for Reporting Damage

2.3 Damage classification.

2.4 Remedial Measures.

WEEK WEEK 6 6 UNDERPINNING UNDERPINNING AND AND SHORINGSHORING

2.4 Underpinning.

2.4 Underpinning Procedure.

2.4 Shoring.

WEEK WEEK 7 7 WALLSWALLS

3.1 Brickwall/Blockwall

3.2 Causes of Defects in Brickwall/Blockwall.

WEEK WEEK 8 8 WALLS WALLS (Contd.)(Contd.)

3.3 Remedial Actions for Wall Defects.

3.3 Repairs to Brickwall/blockwall.

3.3 Repair to Cracks.

WEEK WEEK 9 9 CONCRETE CONCRETE DEFECTSDEFECTS

3.1 Factors Affecting Concrete Durability

3.2 Types and Causes of Concrete Defects.

3.3 Repairs of Concrete Structures.

WEEK WEEK 10 10 STONE STONE WORK.WORK.

3.1 Requirement of Building Stones.

3.2 Causes and Defects in Stonework.

3.3 Repairs of Stonework.

3.3 Clearing of Stonework.

WEEK WEEK 11 11 TIMBER TIMBER AND AND TIMBER TIMBER ROOF ROOF DEFECTSDEFECTS

4.1 Defects in Timber

4.2 Defects in Timber Roofs.

4.3 Timber Roof Remedial Measures.

WEEK12 WEEK12 PAINTING PAINTING DEFECTSDEFECTS

4.0 Defects in Paintwork.

WEEK13 WEEK13 DAMPNESS DAMPNESS IN IN BUILDINGSBUILDINGS

4.4 Causes of Dampness.

4.4 Remedial Measures.

WEEK WEEK 14 14 SITE SITE VISITVISIT

Students’ Report.

WEEK WEEK 15 15 TECHNOLOGY TECHNOLOGY OF OF MAINTENANCEMAINTENANCE

4.6 Technology of Maintenance

4.6 Terotechnology

4.6 Role of Maintenance..

WEEK 1: WEEK 1: BUILDING MBUILDING MAINTENANCE TERAINTENANCE TERMINOLOGIESMINOLOGIES

INTRODUCTIONINTRODUCTION

Building maintenance technology essentially deals with the study of the occurrence of building

defects and the remedies which such defects would require. The maintenance of the built

environment affects everyone continually, for it is on the state of our homes, offices and factories

that we depend not only for our comfort, but for our economic survival. Maintenance starts the

day the Builder leaves the site. Design, materials, workmanship, function, use and their inter-

relationship, will determine the amount of maintenance required during the lifetime of the

building. Effective building maintenance requires the correct diagnosis of defects, and

implementation of the correct remedial measures, all based on sound technical knowledge. It is

highly desirable but hardly feasible to produce buildings that are maintenance free, although

much can be done at design stage to reduce the amount of subsequent maintenance work.

Understanding some basic terms and concepts used in maintenance is necessary in order to learn

maintenance technology.

BS3811 defines maintenance as work undertaken in order to keep or restore every facility i.e.

every part of the site, building and contents to an acceptable standard. It went further to define it

as the combination of all technical and associated administrative actions intended to retain an

item in, or restore it to, a state in which it can perform its required function.

(1.1)Building Maintenance Terms(1.1)Building Maintenance Terms

In order that maintenance activities are carried out efficiently, various forms of management

have developed:-

Property management is an economic service designed to create the greatest possible net return

from a land and its buildings, taken over their remaining economic life.

Maintenance management involves the organising of resources to deal with the problems of

maintenance:

• Building maintenance technology essentially deals with the study of occurrence of building

defects and remedies which defects would require. It involves the application of the

principles of physical sciences to the process of determining the effects on building

performance.

• Building maintenance management involves describing how a system of maintenance effort

could be organised to deal with the problems of building maintenance as a whole. Aside from

locating and rectifying defects, an effective programme to curb maintenance costs must start

with the design of the building itself. This must justify itself, not only in terms of minimising

cost of maintenance, but also in maximizing the benefit of the investment. This means that

financial consideration and techniques play a vital role.

(1.1)Types of maintenance(1.1)Types of maintenance

BS3811 subdivides maintenance into planned and unplanned.

Planned Maintenance:Planned Maintenance:

Planned preventive maintenancePlanned preventive maintenance is work directed to the prevention of failure of facility carried

out within the expected life of the facility to ensure its continued operation.

Planned corrective maintenancePlanned corrective maintenance is work performed to restore a facility to operation or to an

acceptable standard.

Predictable maintenancePredictable maintenance is regular periodic work that may be necessary to retain the

performance characteristics of a product as well as that required to replace or repair the product

after it has achieved a useful life span.

Unplanned Maintenance:Unplanned Maintenance:

Unpredictable maintenanceUnpredictable maintenance is work resulting from unforeseen breakdowns or damage due to

external causes

Avoidable maintenanceAvoidable maintenance is work required to rectify failures caused by incorrect design, incorrect

installation or the use of faulty materials.

(1.2)Nature of Maintenance(1.2)Nature of Maintenance

Proper maintenance of buildings covers many aspects of work which may be divided into four

categories.

ServicingServicing – This is essentially a cleaning operation. The frequency of cleaning varies and issometimes called day – day maintenance e.g. floors are swept daily, windows washed monthly

and painting done every 3-5 years. As more sophisticated equipment is introduced so more

complicated service schedules become necessary.

Rectification work –Rectification work – Usually occurs fairly early in life of the building because of design

shortcomings, inherent fault in use of materials or faulty construction. These short comings often

affect the performance of the component. Rectification represents a point at which to reduce the

cost of maintenance, because it is avoidable. All that is necessary is to ensure that components

and materials are suitable for their purpose and are correctly installed.

Replacement –Replacement – Service conditions cause materials to decay and there is need to consider

replacement. Much replacement work stems not so much from physical breakdown of the

materials or element as from deterioration of appearance. The frequency of replacement could

often be reduced by the use of better quality materials and components.

Renovation or Modernisation –Renovation or Modernisation – This is concerned with alteration, addition and enhancement to

existing buildings, on both small and large scale. It also includes all work designed either to

expand the capacity of a facility or to enable the facility to perform some new functions.

(1.2)Maintenance Needs(1.2)Maintenance Needs

Main purposes of maintenance of buildings are:-

Retaining value of investment

Maintaining the building in a condition in which it continues to fulfil its functions.

Presenting a good appearance.

Self Assess QuestionsSelf Assess Questions

1) Discuss the persons that should be held responsible for causing avoidable maintenance in not

more than one page.

2) Identify the role the house owner or occupant plays in the maintenance of his property in not

more two paragraphs

3) State three reasons why we need maintenance?

WEEK 2: CAUSES AND AGENTS OF DETERIORATION OF BUILDINGSWEEK 2: CAUSES AND AGENTS OF DETERIORATION OF BUILDINGS


A building must meet various requirements and withstand the rigours of climate, and at the same

time it is expected to last for many years, preferable with minimal maintenance. Consideration

must be given at every stage of the building process of ways of reducing the incidence of defects

and prolong the durability of the building.Understanding the causes and agents of deterioration in

buildings, is quite necessary to reduce the incidence of defects.

(1.2)Common Factors of Deterioration(1.2)Common Factors of Deterioration

There are a number of factors that lead to maintenance growth, they include:-

a)Ageing Stock of Buildingsa)Ageing Stock of Buildings – more expenditure is expected for maintenance because of the

ageing of the building especially in developed countries.

b)Obsolescence of Buildingsb)Obsolescence of Buildings – upgrading needed to buildings to prevent their obsolescence.

This is because developments face keen competitions to attract new tenants or to retain existing

ones.

c)Advent of New Technologiesc)Advent of New Technologies – Changes and modification to existing buildings are required to

meet new demands. Such changes are likely to be carried out by renovation or retrofitting of

existing buildings.

d)Rising Social Expectation and Aspirationd)Rising Social Expectation and Aspiration - The natural increase in aspirations and

purchasing power will expand the market for higher standards of both maintenance and

retrofitting work, already particularly evident in residential premises.

e)New Legal Developmentse)New Legal Developments – This imposes an increased burden on building owners to maintain

and keep their premises safe. These developments will push for higher standards and a greater

degree of professionalism and thoroughness in the execution of maintenance work.

f)Environmental Issuesf)Environmental Issues – protective measures against pollution, erosion, etc.

In order to understand the causes and agents of deterioration and defects in buildings,

consideration must be given to every stage of building process.

(1.2)Causes and Agents of Deterioration(1.2)Causes and Agents of Deterioration

Design DeficienciesDesign Deficiencies

Many of the subsequent maintenance problems are directly attributed to decisions made at the

design stage of the building. These decisions can be broadly classified into several categories:-

a)Approach to Designa)Approach to Design

Many maintenance problems arise where design is sound in principle but has a low probability of

satisfactory achievement in practice. Some designers fail to realise that their design can be too

complex for site condition and can present problems of buildability. The designer must be fully

aware of the clients needs. Defects often occur because of a lack of understanding of how a

building is to be used. Inadequacies and faults also result from the owners’ and designer’s

attempt to provide too much with insufficient money

b)Selection or Choice of Materialsb)Selection or Choice of Materials

Many materials are satisfactory in some conditions but not in others. The choice of design details

in relation to the materials to be used and in relation to the proposed use of the building and its

environment is the factor most affecting the risk of defect or failures. The designer must either

design to suit the materials available or for a required design, choose materials which may be

expected to perform satisfactorily with that design in the given environment. It is also necessary

to consider the likely behaviour of combinations of different material in use, for there are many

examples of such combinations which give rise to problems that arise from chemical interaction

or differential involvement.

c)Environmental Factors.c)Environmental Factors.

The factors arising from above ground condition will usually include climate, atmospheric

condition, and atmospheric pollution and exposure conditions. Below ground factors will include

nature of soil, drainage and site stability. Hence sunlight, wind, rainfall, temperatures and

atmospheric humidity have profound effects upon the durability of materials and their behaviour.

d)Building Shape and Formd)Building Shape and Form.

Building maintenance consumes a large proportion of material resources. Attention should be

paid to designing buildings which will cut down maintenance expenditure in the future. The

influence of building shape and form on maintenance expenditure in profound.

e)Orientation of Buildinge)Orientation of Building

The orientation or arrangement of the axis of a building is a way of controlling the effects of the

sun, wind and rain. The building may be orientated to capture the heat of the sun or conversely it

may be turned to evade the solar heat in the tropics. Orientation may also be used to control air

flow circulation and reduce the disadvantages of wind, rain and snow when prevailing currents

are predictable.

f)Design and Maintainabilityf)Design and Maintainability

Designers often give too much emphasis to aesthetics at the expense of maintainability. There

must be continuous interaction between consultants and maintenance managers in the initial

planning as well as in the final design of the building.

Construction FaultsConstruction Faults

Inadequate supervision and the substitution of poor materials, components or fixing could lead to

deterioration of buildings. In view of this there is need for stringent control of the work on the

site as well as the materials used for the construction.

a)Control of Works on Sitea)Control of Works on Site

Careful supervision of building work at all stages is necessary to complement good designs,specification and detailing by the designers.

b)Control of Materialsb)Control of Materials

Materials used in buildings must normally be purchased according to the specification or to be

similar to an agreed sample. Materials which do not comply with the specification should be

rejected.

c)Lack of Maintenancec)Lack of Maintenance

The clients brief for a new building often determines the long-term maintenance needs of the

building. The brief should indicate performance requirements and possible changes in use, as

well as future policy for operating, cleaning and maintaining the building. Designers should

provide advice to the client on maintenance matters. Users of the building should also show

serious commitment toward maintenance.

d)Change of Use of Buildingd)Change of Use of Building

Buildings are normally designed for a specific use. During design stage the designers will make

provision for that use only. Problems arise when alteration of change of use by the owners or

users occur without the designers being consulted before hand.

e)Vandalisme)Vandalism

Vandalism is caused by wilful damage to the building or structure. Other factors also increase the

incidence of the vandalism, lack of security, wrong choice of materials, poor space layout, poor

lighting arrangement etc. Any act of vandalism will affect the aesthetic appearance of the

material or component. The end result in higher maintenance costs.

Weathering AgentsWeathering Agents

a)Solar Radiationa)Solar Radiation

Solar radiation is received at the surface of the earth directly and as diffused long-wave radiation.

Solar radiation affects building materials is two ways:

i)Chemical effect of visible and infrared radiation will speed up the rate of deterioration carried

by other agents.

ii)Dimensional change in material that occurs when solar radiation is absorbed when it strikes a

material.

b)Moistureb)Moisture

Moisture is the principal agent of deterioration and is probably also the agent with the greatestinfluence on the properties of materials. In many cases, moisture is a prerequisite for physical,

chemical or biological reactions to take place.

c)Windc)Wind

Wind can cause direct damage by the removal of part of a building. It can cause dampness by

driving moisture into or through a building fabric and excessive heat losses from the interior of a

building by uncontrolled air changes.

d)Driving Raind)Driving Rain

The effect of driving rain is that the vertical surfaces facing the wind receive rainwater at an

angle. Constructional details could be used to minimise its deteriorating effect.

e)Atmospheric Gases.e)Atmospheric Gases.

In the presence of moisture, these gases contribute to the formation of acids that attack certain

materials; such gases include sulphur dioxide, carbon dioxide, oxygen and ozone.

Chemical AgentsChemical Agents

a)Corrosiona)Corrosion

Atmospheric corrosion mean an oxidation process where metal combines with oxygen in the air

to form rust. The process is usually accompanied by expansion of the metal which can affect

adjacent materials.

b)Sulphate Attackb)Sulphate Attack

In persistently damp condition, sulphates will react slowly with tri-calcium aluminates (a

constituent of Portland cement and hydraulic lime) which causes the cement render or mortar to

expand and eventually disintegrate.

c)Crystallisation of Salt.c)Crystallisation of Salt.

Soluble salts may be present initially in certain building materials or may be conveyed into them

by movement of moisture from the ground or adjoining materials. When moisture gets into a

material and evaporates from the surface, the concentration of the salt in solution increases until

it crystallises out. It could cause surface disfiguring.

Biological AgentsBiological Agents

Attack by rodents, insects, fungi, algae and plants may cause serious deterioration in various

parts of a building..

Mechanical AgentsMechanical Agents

Mechanical agents are those which tend to impose a physical force on building. They can be

static and permanent such as ground pressure or dynamic such as wind and vibrations.


1. Identify three causes of deterioration peculiar to buildings in industrial areas.

2. In not more than a page and a half discuss how design deficiencies increase maintenance?

3. How can negligence/ignorance of the builder increase maintenance needs? Discuss this in not

more than a page.

4. With the aid of five pictures show the role of weathering agents in the deterioration of

building works.

WEEK3: DIAGNOSIS AND WEEK3: DIAGNOSIS AND INVESTIGATIONINVESTIGATION


There is need to understand why and how defects occur, what the implications are and what

remedial measures are necessary to restore, maintain or extend the usefulness and safety of

buildings. Out of this need has arisen a discipline described as building diagnostics.

(1.1)Diagnosis Terminology(1.1)Diagnosis Terminology

Building DiagnosticBuilding Diagnostic

Building diagnostic involves a process in which relevant experts investigate the existing

condition of a building, carryout the necessary tests, evaluate the data collected, make

recommendation professionally, and predict the future performance of the building. The process

makes use of a variety of techniques, ranging from visual inspection to sophisticated

instrumentation. It is obvious that building diagnostics involves experts from a wide range of

disciplines.

(1.2)Need for Building Diagnosis(1.2)Need for Building Diagnosis

During the life of a building, there will be many occasions when the physical condition of the

building may have deteriorated thus affecting its continued use. The building owner should know

when such occasions occur so that relevant experts may be called to arrest the problems in time.

Diagnostic assessment will be required under the following circumstances:-

a)Persistent Defectsa)Persistent Defects: Persistent defects such as cracks and deformations which appear to

worsen progressively or become widespread may need thorough diagnostic assessment to

determine the causes.

b) Ageing Structureb) Ageing Structure: It is advisable that old buildings be checked periodically to determine the

presence and effects of hidden defects such as decreasing concrete strength or corrosion of steel

reinforcement.

c) Change of Use or Rehabilitationc) Change of Use or Rehabilitation: A diagnostic assessment should be considered to examine

the suitability of the new usage and the extent of rehabilitation work required.

d) Sale of Propertyd) Sale of Property: A diagnostic assessment should be considered to know the condition of the

building, disclose to the purchaser the defects and their rectification and subsequently give

financial institutions a basis for arriving at a value for loans.

e) Post-Crisis Assessmente) Post-Crisis Assessment: After severe crises such as fire an assessment is necessary to

ascertain the structural stability and safety of buildings.

(1.2)Process of Investigation(1.2)Process of Investigation

A plan of action has to be drawn up to make sure that the investigation process progresses

without unnecessary inconvenience to occupant of the building and the process entails several

steps:

a)a) Preliminaries:Preliminaries: Documentation survey on maintenance records, design and as-built drawings,

specifications etc.

b)b) Visual Inspection:Visual Inspection: On-site investigation relying mainly on sight, hearing, touch and smell.

Additional information may be obtained by conducting interviews with occupants and

maintenance personnel. Visual inspection is essential as it may lead to selection of other

methods of investigation.

c)c) Testing and MonitoringTesting and Monitoring: Techniques which include non destructive semi destructive tests,

destructive tests and chemical and physical analysis of materials.

d)d) Exploratory WorksExploratory Works: Include the techniques of removing obstructions to facilitate a closer

inspection of hidden parts of a building.

(1.2)Remedial Measure RecommendationRemedial Measure Recommendation

Making recommendations is a very difficult task as there are many alternatives in repair work.

Remedial work chosen may belong to one of three general categories:-

a) Patching Upa) Patching Up: Very popular because of lower costs involved, but should always be regarded

as a temporary measure.

b)Replacement of Partsb)Replacement of Parts: First consideration to give a permanent repair.

c)Complete Renewalc)Complete Renewal: Most economic solution for buildings for longer life.


1. Identify four tests that are carried out during maintenance operations

2. Mention four reasons for the need for building diagnosis.

3. Identify a scenario where each of the three remedial works could be applied.

WEEK 4: FOUNDATION DEFECTSWEEK 4: FOUNDATION DEFECTS


The most expensive building repair bills are often incurred with foundation failures. The soil that

support the foundation is bound to be disturbed during construction and with the increased

loading some movement and settlement must be expected. Soil conditions have an important

influence on foundation design and the subsequent behaviour of buildings. Therefore prior to

designing foundation, it is necessary to identify the soils characteristics present on the site.

(2.1)Causes of Foundation Defects(2.1)Causes of Foundation Defects

The extent of foundation movement depends on the nature of the soil and the amount of imposed

loads. Thus a good foundation design must take into consideration not only the type of structure

to be supported but also the soil conditions.

a)Movement of Soilsa)Movement of Soils

i)Clay Soilsi)Clay Soils: clays, which shrink on drying and swell again when welted, are commonly

responsible for the movement of shallow foundations. The shrinking when drying isaccompanied by an increase in bearing strength, while the swelling when wet reduces its bearing

strength(Fig 4.1).

Fig 4.1. Cracking associated with shallow foundations on shrinkable clay.

ii)Sandy Soilsii)Sandy Soils: Dense beds of sand form excellent foundation soils, but underground water can

wash out the finer particles, leaving coarser material in a less stable condition. Much of the

bearing capacity of the sand may be lost in such circumstances (Fig 4.2).

Fig 4.2. Washing out of fine sand particles by underground water.

Fig 4.3. Settlement caused by consolidation of soil.

iii)Organic Soils in Made-up Groundiii)Organic Soils in Made-up Ground: Peats and other soils which contain a high proportion of

organic matter from decaying vegetation vary greatly in volume as their water content changes.

These soils are highly compressible so that they can even settle readily under their own weight,therefore the bearing capacities of such soils are poor and they should not be used for

construction purposes unless deep foundation passing through the fill can be designed and

provided economically(Fig 4.3).

iv)Swallow Holes in Lime Stones:-iv)Swallow Holes in Lime Stones:- In chalk or lime stone areas, cavities in the bedrock can

form by the action of subterranean streams dissolving the rock away. When the overburden

collapses into a cavity, a swallow hole is formed at the surface, causing serious damage to the

buildings above or near to the site(Fig 4.4).

Fig 4.4. Formation of ‘Swallow Hole’ in limestone.

b)Other Movementsb)Other Movements

i)Effects of Vegetationi)Effects of Vegetation: The extraction of moisture by tree roots in shrinkable clay will cause

the soil to shrink. If this shrinkage takes place under the foundation there is a tendency for it to

settle thus affecting the stability of the building (Fig 4.5).

ii)Slopes and Excavationsii)Slopes and Excavations: Clay soils on slopes exceeding 1 in 10 are likely to move down hill

slowly, which may be subject to creep and this could result in heavy pressure on walls.

Fig 4.5. Cracking arising from drying action of tree rootsFig 4.5. Cracking arising from drying action of tree roots

iii) Vibration and Sudden Shocksiii) Vibration and Sudden Shocks: Vibration may be caused by traffic or machinery and if

these vibrations are prolonged and intense they can affect the foundation of older buildings

causing them to settle gradually. An explosion can generate sudden shocks which can affect the

stability of the building structure and ground support(Fig 4.6).

Fig 4.6. Effects of vibration and sudden shocksFig 4.6. Effects of vibration and sudden shocks

iv)Mining Subsidenceiv)Mining Subsidence: Buildings above mine tunnels can suffer deformation as the ground

subsides over the workings. Initially the buildings tend to tilt but subsequently the tilt decreases

and the settlement increases as the ground below is affected(Plate 4.1).

Plate.4.1. Effects of mining subsidence.

v)Differential Settlementv)Differential Settlement: When settlement is uniform over the whole area of the building, it is

very unlikely to cause any damage to the superstructure. Damage is usually the result of what is

known as differential settlement in which one side of the building subsides more than another,

leading to cracks and stresses in the superstructure(Fig 4.8 & Fig 4.9)

Fig 4.8 Settlement at the ends of a wallFig 4.8 Settlement at the ends of a wall

Fig 4.9 Sagging under the centre sectionFig 4.9 Sagging under the centre section

Self Assess Questions:Self Assess Questions:

1. Identify the common causes of failures of foundation under the following scenario:

a. Sandy desert area like Sokoto

b. Marshy rainy area like Bayelsa

2. Identify five things that reveal foundation failuress of a building.

WEEK 5: FOUNDATIONS (ASSESSMENT AND REMEDIAL WEEK 5: FOUNDATIONS (ASSESSMENT AND REMEDIAL MEASURES)MEASURES)


Most failure in foundation manifests in walls as cracks. These cracks could be in tension,

compression or shear and they may be of varying width sizes and direction. In order to arrive at a

correct remedial action to be taken, an assessment and classification of the defect must be carried

out.

(2.3)Assessment of Foundation Defects(2.3)Assessment of Foundation Defects

The assessment of any defect in foundation involves identifying the form of the superstructure,

the substructure as well as the soil, and the determination how well they behave in combination.

According to BS 5930, investigation should follow these guidelines:-

• Visual inspection of the building taking note of any cracking and distortion.

• Examination of old building plans

• Examination of the geology, topography and water level records of the area, including nearby

trees.

• Exposure of the substructure by trial pits and boreholes to assess ground conditions.

(2.3)Procedure for Reporting Damage(2.3)Procedure for Reporting Damage

a)Determine position and direction of cracks

b)Distinguish where possible between tensile cracks, compressive cracks and shear cracks.

c)Determine approximate age of cracks by interviewing occupants.

d)Estimate the magnitude of any distortion or movement of the building, i.e. tilting, bulging or

sloping.

e)Record any impediment to serviceability e.g. jammed door or windows, breakdown of services

etc.

f)Report condition of the walls and finishes.

(2.3)Damage Classification(2.3)Damage Classification

Damage can be classified as failures that affect:

• Aesthetic appearance of the building

• Service ability of certain parts of the building which result in fracturing of service pipes,

jamming of doors and windows and breakdown of services in the building.

• Stability of the building and require extensive repairs to foundations.

(2.4)Remedial Measures(2.4)Remedial Measures

Remedial measures are generally difficult and expensive. Generally the remedial measure

recommended for foundation failures is to underpin the whole external walls. However in clay

soils, where damage is not severe or the building is old, it may be adequate to reduce further

movements by surrounding the building with a relatively impervious apron of precast slabs or in

site concrete to a with of 1.50m.

The remedial action for effect of vegetation takes two forms, where trees have not reached

maturity it is good practice to cut them down and kill the stump, as the ground under the building

will slowly swell during the wet season, and tend to lift the building and partially close the

cracks. If the trees have reached maturity and the building is fairly old, it is unlikely that further

movements will occur. In this situation it would be best to leave the trees in position and merely

fill up the cracks in the building.

Repairs to cracks in walls will depend on the magnitude of the cracks. It ranges from hairline

cracks which are negligible to very severe cracks which involve partial or complete rebuilding.

Hairline cracks of less than 1mm wide can be easily camouflaged by normal redecoration or

filled with cement shinny.

Minor cracks which is rectified by chiseling and filling with concrete/mortar as required.

Major cracks which require extensive and expensive repair methods such as chiseling

blockworrk, introduction of rods and ties and filling. It may also involve stabilizing the

foundation.

Case Study ProblemCase Study Problem

Go round your campus and take at least six pictures of different cracks that may be as a result of

foundation failures and write a report using the format above.

WEEK 6 : WEEK 6 : UNDERPINNING AND SHORINGUNDERPINNING AND SHORING


Underpinning is a highly skilled operation and should be undertaken by experienced firms. No

one is like the other and each must be given individual consideration for the most economical

and safest scheme to be worked out. It is also generally necessary to provide extensive support

through shoring to buildings while excavating close to their foundations or while underpinning

their foundations.

(2.4)Underpinning(2.4)Underpinning

Underpinning a structure is required:

a) To support a structure which is sinking or tilting due to ground subsidence or instability of the

superstructure.

b) As a safe guard against possible settlement of a structure when excavating close to or below

its foundation level.

c) To enable the foundation to be deepened for structural reasons, e.g. to construct a basement

beneath a building.

d) To increase the width of a foundation to permit heavier loads to be carried, e.g. increasing the

storey height of a building.

e) To enable a building to be moved bodily to a new site.

Before any underpinning work is commenced the building should be carefully examined and any

urgent repairs carried out. It is important to carry out a soil investigation to determine allowable

bearing pressures for the new foundation. It is also important to recognize the true cause of

settlement and if underpinning is necessary to arrest settlement, underpinned foundation should

be taken down to relatively unyielding ground below the zone of subsidence. The structure to be

underpinned should first be supported with shores.

(2.4) Underpinning Procedure.(2.4) Underpinning Procedure.

1. Excavate rectangular pits or legs at intervals beneath the existing foundation.

2. Pits are then filled with concrete or brickwork up to the underside of the existing foundation.

3. After, intervening legs are excavated and the concrete or brickwork constructed within them

to bond on to the brickwork already in place.

4. Maximum length of wall which can be left unsupported above each leg is usually 1.2 to 1.5m

of normal construction.

5. The unsupported length should be equally distributed over the length of the wall.

6. The sum of the unsupported lengths should not exceed one-quarter of the total length of the

structure.

7. Legs should be dealt with in groups of six in the sequence 1,2,3,4,5,6(Fig 6.1).

Fig. 6.1. Underpinning.Fig. 6.1. Underpinning.

8. If the wall is heavily loaded or shows signs of structural weakness, the unsupported length at

any given point should not exceed one-fifth to one-sixth of its total length.

9. Concrete should be placed as quickly as possible after completion of excavation in each leg.

10. Blockwork or brickwork can be used to fill the spacing between the top of the underpinning

concrete and the underside of the existing foundation.

11. When excavating each hole or leg sufficient space is allowed in front of the wall to provide

adequate working space.

12. No earth faces should be left unsupported overnight.

Other methods of underpinning also exists which could be employed for cases where this

traditional method (Fig 6.2) is not well suited.

Fig.6.2. Traditional methods of underpinning strip foundationsFig.6.2. Traditional methods of underpinning strip foundations

(2.4) Shoring(2.4) Shoring

Shoring is needed to give temporary support to walls and floors during alteration, demolition or

underpinning (Fig 6.3) or where a building has become unsafe. Shoring of a structure is

required:-

a) To support a structure which is sinking or tilting due to ground subsidence or instability of

superstructure.

b) As a safeguard against possible settlement of a structure when excavating close to and below

its foundation level.

c)To support a structure while making alterations to its foundation or main supporting of timber

and there are three

types

Fig. 6.3 ShoringFig. 6.3 Shoring

Dead Shores:Dead Shores: The purpose of dead shores is to support dead and superimposed loads of a

building, mainly while alteration and repair work is in progress. Dead shores are vertical struts

bearing on the ground at the required distance away from the wall to be clear of underpinning

operations and surmounted by a horizontal beam or needle spanning between the pair of shores.

They must be securely braced together and provided with a firm bearing. If the ground has a low

bearing capacity, a mat or grillage should be provided (Fig 6.4).

Raking ShoresRaking Shores: Raking shores may be used to provide temporary support to a wall which has

become defective and unsafe, or as a precautionary measure while alteration work is being

undertaken. The arrangement of the shores will depend on the height of the building, loads to be

carried, extent of openings and space available adjacent to the building. The angle of the shores

with the ground is generally between 45 to 75 degree (Fig 6.5).

Fig. 6.4 Dead shoreFig. 6.4 Dead shore

Flying Shores:Flying Shores: Flying shores are used to provide support between buildings, where an

intervening building has been demolished, or across a narrow street or alley. Flying shores can

be used where the feet of raking shores obstruct construction operations. The use of this type of

shore is restricted to spans of 4.50 to 10.5m at spacing of 2.5 to 4.om. Because flying shores do

not bear on the ground, they cannot carry the weight of a wall; they merely provide restraint

against bulging and tilting (Fig 6.6).

Fig. 6.5 Raking shoreFig. 6.5 Raking shore

Fig. 6.6 Flying shore.Fig. 6.6 Flying shore.

Self Assess Questions:

1. In two paragraphs, discuss hazards associated with underpinning and shoring.

2. Identify the major differences between the various types of shores.

WEEK7: WALLSWEEK7: WALLS


A wall is a vertical structure forming an inside or an outside surface of a building, usually built

of stone, wood, plaster or brick, which acts as a boundary or keeps something in or out. Walls

suffer particularly from the following defects:-

• Inability to support imposed loads, resulting in distortion or cracking

• Inability to keep out the weather

• Inability to insulate from cold with resultant condensation

• Deterioration

The defects that occur in walls may be as a result of inherent faults, deficiencies in production,

design, materials or workmanship, and attack by environmental agents.

(3.1) Brickwall/Blockwall(3.1) Brickwall/Blockwall

The majority of bricks in general use are made of clay, however, other materials like sandlime,

flintlime, concrete, etc, can also be used to make bricks.

(3.2) Causes of Defects in Brickwall/Blockwall(3.2) Causes of Defects in Brickwall/Blockwall

Brickwork/blockwork defects arise in a variety of ways but the general causes of defects in

brickwork are:

a) Productiona) Production: these are inherent defects in the bricks/blocks during production and after but

before they are being used for the brickwork. The bricks may have defects in size, shape,

appearance, body and storage (Fig 7.1).

b) Mortarb) Mortar: the mortar for jointing should be of the quality to achieve workability, water

retentivity, strength, bond, durability and good appearance and texture. Mortal should be of the

same strength and consistency as the mix used for producing the blocks

Fig. 7.1. Production defectsFig. 7.1. Production defects

.

c) Efflorescencec) Efflorescence: Efflorescence on brickwork can be seen as a white or whitish deposit of saltson the exposed surfaces of the bricks; especially new brickwork. Efflorescence is caused by the

migration of salts from the interior to the surface of the bricks/blocks. Any absorbed water

drying out in the bricks will leave the salts behind. It can occur on internal as well as external

surface causing damage to decorations. External efflorescence although unsightly is rarely a

serious problem because the salts are washed away by rain. Internal efflorescence is usually

more troublesome as the plaster could be pushed off the walls. Therefore, where efflorescence

can be expected, decorative treatments on walls should not be applied hastily(Plate 7.1).

d) Stainsd) Stains: These may be white like efflorescence, but do not disappear when the

brickwork/blockwork is washed by rain. These stains are due to calcium hydroxide produced

during hydration of Portland cement reacting with carbon dioxide in the atmosphere to form

calcium carbonate, an insoluble while crystalline solid. This will form a disfiguring stain on the

brickwork/blockwork.

Plate 7.1. Effect of efflorescence on blockwork/brickworkPlate 7.1. Effect of efflorescence on blockwork/brickwork

e) Impuritiese) Impurities: The presence of lime nodules, vegetable matter, unoxidised carbon materials, and

other foreign matter or materials due to faulty screening during production of bricks/blocks may

cause spalling in the case of facing bricks or disintegration of plaster.

f) Sulphate Attackf) Sulphate Attack: Sulphate attack on walls is the result of the reaction of tri calcium

calumniate present in all ordinary Portland cements with sulphates in solution. This can cause

considerable expansion, disintegration of mortar joints and distortion of wall.’

g) Moisture Movementg) Moisture Movement: Excessive expansion and contraction due to moisture content can

produce shrinkable cracks (Plate 7.2).

Plate 7.2. Moisture movement in blockwork/brickworkPlate 7.2. Moisture movement in blockwork/brickwork

h) Thermal MovementThermal Movement: vertical and horizontal movements occur in brickwork/blockwork due

to the effect of heat which may or may not be reversible resulting in cracks(Plate 7.3).

Plate 7.3. Thermal movement in blockwork/brickwork.Plate 7.3. Thermal movement in blockwork/brickwork.

i) Bulging, Buckling and Spreadingi) Bulging, Buckling and Spreading:- Bulging and buckling of walls may be caused by the

outward spreading of external walls, either vertically between ground level and the roof or

horizontally between the walls(Plate 7.4 & 7.5). The main causes of these problems are:-

1. Vibration from machinery, plant or traffic.

2. Overloading of the structure i.e. increased loads on floors or adding more structures.

3. High slenderness ratio which is inadequate thickness in relation to height.

4. Lack of cross ties between the outer wall structures.

This defect takes the form of a gap between the wall and the floor. Spreading, however, occurs at

roof level when the roof sags.

Plate 7.4. Buckling in blockwork/brickworkPlate 7.4. Buckling in blockwork/brickwork

Plate 7.5. Bulging in blockwork/brickworkPlate 7.5. Bulging in blockwork/brickwork

j)Ground j)Ground Movement Movement or or SettlementSettlement: Normal slight overall settlement of a building should not

affect the brickwork. However, differential settlement often resulting in cracked walls may occur

where there are sudden changes in ground conditions over the site or where there is inadequately

consolidated fill under foundations. Settlement cracks are usually diagonal and often appear at

door and window opening, these being the weakest parts of the wall.

k)Atmospheric Impuritiesk)Atmospheric Impurities:- Dust particles in contact with bricks and moisture from weak acids.

This causes deterioration of brick surface, which allow surface erosion.

l)Lichen, Moulds and Other Growthsl)Lichen, Moulds and Other Growths:- These organisms are rarely destructive but they do

produce disfiguring stains on brickwork/blockwall and other wall surfaces. Climbing and other

plants growing on walls can cause damage to walls but much depends on the condition of the

wall and the extent to which the growth of the plants is controlled(Plates 7.6 & 7.7).

Plate 7.6. Mould growths in blockwork/brickworkPlate 7.6. Mould growths in blockwork/brickwork

Plate 7.7. Lichen growths in blockwork/brickworkPlate 7.7. Lichen growths in blockwork/brickwork

Self Assess Questions:Self Assess Questions:

1. Identify five causes of deterioration on bricks/blockwork that are likely to cause cracks.

2. Classify the causes of deterioration of brick/blockwork under the following headings:

• Inherent faults.

• Deficiencies in production.

• Design

• Workmanship

• Materials.

• Attack by environmental agents.

WEEK 8: WALLS(CONTINUE )WEEK 8: WALLS(CONTINUE )


It is not always easy to judge from appearance how serious a defect is likely to affect the strength

and stability of a structure. Generally if walls are not too distorted or too out of alignment, it may

be taken that the damage may not be too serious, therefore when the damage is not sufficient to

affect the structural stability, the repairs can be carried out easily, but if it does, it should be

demolished to avoid disaster.

(3.3) Remedial Actions for Wall Defects(3.3) Remedial Actions for Wall Defects

(3.3) Repairs to Brickwork/Blockwork(3.3) Repairs to Brickwork/Blockwork

a) Production Defectsa) Production Defects:- It is very important to inspect, select and store bricks/blocks

appropriately before use to avoid defect that are caused by production and storage. In any defect

noticed after use, it is advisable to chisel out the portion and replaster.

b) Mortarb) Mortar: It is important to use an appropriate mortar, properly batched, and adequately mixed,

using the same mix throughout and taking adequate precautions.

c) Efflorescencec) Efflorescence: Efflorescence is normally washed away by rain/water and no special treatment

is needed. To accelerate removal, the brickwork/blockwork can be dry brushed periodically until

the soluble salts cease to crystalline. Precautionary measure should be taken before use to ensure

that the mix of materials is free from soluble salts.

d) Stainsd) Stains: The normal remedy for stains is as follows:

1. Thoroughly wet the brickwork/blockwork with clean water

2. Carefully brush on diluted hydrochloric acid

3. When stains have dissolved, thoroughly wash wall with clean water.

4. After removal of stains, flashings should be provided to prevent further percolation and

staining.

e) Sulphate Attacke) Sulphate Attack: In minor cases, affected brickwork/blockwork should be dried out and

moisture excluded as far as practicable. In severe cases rebuilding parts of the structure is

necessary and it is essential to use materials suited to the conditions such as sulphate resisting

cement.

f) Moisture Movementf) Moisture Movement: Most of this defect occur early in the life of the building and are

unlikely to be progressive. It is necessary to use appropriate damp proofing materials and where

defect is noticed, the wall should be wind dried and the drainage around the structure improved.

g) Thermal Movementg) Thermal Movement: Provision should be made for maximum thermal movement, after

rectifying the damage which is usually cracks.

h) Atmospheric Impuritiesh) Atmospheric Impurities: The surface dirt can be removed by washing. In addition, all

defective bricks should be cut out, the wall rebuilt and then repointed.

i) Lichens, Moulds and Other Growths:i) Lichens, Moulds and Other Growths: Such growths can be prevented or destroyed by

applying some toxic washes during a dry spell after partially removing any thick surface

growths. The effectiveness of the treatment depends on the porosity of the surface and the extent

which it is washed by rain.

(3.3)Repair to Cracks(3.3)Repair to Cracks

Cracking of wall usually indicate failure or defective construction. It is unsightly and

unacceptable to the occupants. Cracking often result in air infiltration, heat loss and reduced

sound insulation, all of which cause a reduction in the efficiency of the building. Cracks could

run more or less diagonally, following horizontal and vertical mortar joints or pass straight down

through vertical joints and the intervening bricks/blocks and mortar beds.

Fine cracks of up to 1.5mm wide in joints are usually best left unfilled as they are unlikely to be

harmful. Wider cracks (1.5-3.5mm wide) will generally require repair. The procedure willinvolve raking or cutting out the joints squarely to a depth of about 15mm and repoint with

mortar.

With cracks passing through bricks and mortar, cut out and rebound, using a mortar similar to

that in the existing wall.

Cracks of similar appearance can be due to different causes. When examining cracks care should

be taken to record precisely the direction of the cracks, whether or not they extend through the

wall and whether they taper off in any direction.

Case Study ProblemCase Study Problem

1. Visit a block industry, a building construction site and an abandoned construction site.

Observe any defects and proffer solutions for each. Use pictures to buttress your observation.

WEEK 9- CONCRETE DEFECTSWEEK 9- CONCRETE DEFECTS


Concrete by nature, is a non uniform, non isotropic structural material consisting of aggregate

particle air voids and moisture. Variation in production and subsequent attack by its environment

means that concrete is not totally immune to defect although it is generally a durable and

maintenance free material. There is therefore a need for regular inspection of all reinforced

concrete structure so that any deterioration can be detected at its early stages, and a decision

taken on remedial works.

(3.1) Factor Affecting Concrete Durability(3.1) Factor Affecting Concrete Durability

These could be classified into:

a) Faulty design which includes wrong mix proportion, inadequate joint provision e.g. expansion

joints and under design of the concrete elements such as inadequate reinforcement.

b) Inferior materials which is caused by use of partially hydrated cement, contaminated water or

aggregates.

c) Poor construction practice which is caused by faulty formwork, improper placing causing

segregation and inadequate curing causing shrinkage cracks. It could also arise from inadequate

vibration and misplacement of steel.

d) Abuse of structure such as acts of vandalism, lack of maintenance and change of use of the

structure.

e) Environmental effects caused by thermal movement, moisture movement, freezing and

thawing or surface erosion of the concrete structure.

f) Chemical aggression which includes sulphate attack, acid attack, leaching of lime etc.

g) Physical aggression such as abrasion, erosion, cavitations etc.

( 3.2)Types and Causes of Concrete Defects( 3.2)Types and Causes of Concrete Defects

Concrete buildings are subject to movement due to compression of foundation, shrinkage of

concrete, thermal movement, variable loading and wind pressure. Defects of reinforced concrete

member can take the form of surface cracks which are influenced by the effective concrete cover

to the steel reinforcement, and internal cracking where the member is subject to bending. Some

important conclusions that may be obtained from a well executed visual inspection of concrete

structure include the following:-

i) Spalling of concrete indicates corrosion of steel reinforcement. If spalling occurs in spite of

adequate cover, the concrete is likely to be porous and weak (Plate 9.1).

Plate 9.1. Spalling defect in concrete floorsPlate 9.1. Spalling defect in concrete floors

ii) When spalling occurs in flat roof and bathrooms and is accompany by damp and wet patches,

it is likely water penetration is the cause of problem (Plate 9.2).

iii)Vertical and diagonal cracks in beams indicate that the beams may be overstressed in flexure

or shear respectively, either the beams are under-designed or applied loads are higher than those

assumed in design.

iv) Vertical cracks in columns indicate a high level of compressive stress in the members which

tend to split vertically under the lateral bursting pressure and weaken the confining links.

v) Random cracking in floors indicates shrinkage on concrete and lack of movement joints (Plate

9.3).

Plate 9.2. Spalling defect in concrete in flat roofPlate 9.2. Spalling defect in concrete in flat roof

Plate 9.3. Random Cracks in FloorsPlate 9.3. Random Cracks in Floors

vi) Diagonal cracks along walls and at beam ends indicate differential settlement of foundations,

in the case of beams; the diagonal cracks are concentrated towards one end of the beam.

(3.3) Repairs of Concrete Structures(3.3) Repairs of Concrete Structures

Having established the causes of the defect by careful diagnosis the next step should be to

consider the requirement of the repair method. The selection of the correct method and material

for a particular application requires careful consideration, whether to meet special requirement

for placing, strength durability or other short or long term properties. The first step in the repair

process is to cut away all loose or deteriorated concrete until the sound concrete core is reached.

Cutting back should be at right angle to the external surfaces. All exposed reinforcement must be

thoroughly cleaned. The formwork must be designed so that the concrete will fill it completelyand there must be adequate access for compaction purposes. The method used to place the

concrete are usually similar to those used in new work, except the quantities are smaller. Before

any crack is repaired it is necessary to determine its cause so that the correct method of repair

can be decided. If the cause of the crack is unlikely to reoccur it may be filled with a rigid

material. But if it is caused by movement that is likely to continue, then any attempt to seal the

crack may cause a new crack to appear along side the old one.


1. In the section under causes and effects of concrete defects, identify the causes and effects for

each point.

2. What precautionary measures need to be put in place during the repairs of concrete

structures? Discuss in a page.

WEEK 10: STONE WORKWEEK 10: STONE WORK


Building stones are generally limestone, sandstones, or granite. They are used generally as wall

cladding and facing materials.

(3.1)Requirements of Building Stones(3.1)Requirements of Building Stones

a) Strengtha) Strength:- Building stones should normally be of adequate strength to carry imposed load

especially at lintels and when used for civil engineering work.

b) Moisture Resistanceb) Moisture Resistance: - Building stones hardly absorb water but sandstones may absorb up to

20 percent and are subject to appreciable moisture movement. Penetration of damp is also

unlikely except at window mullions or jambs and at sills, copings etc (Plate 10.1).

c) Compatibilityc) Compatibility: - Damage can result from the use of different types of stones in direct contact

with one another.

d) Durabilityd) Durability:- The durability of stonework is influenced by the stone’s chemical composition

and structure and its performance.

Plate 10.1. Decayed stoneworkPlate 10.1. Decayed stonework

(3.2) Causes and Defects in Stonework(3.2) Causes and Defects in Stonework

a) Continuous wetting and drying of stones by rains and sun causes internal stresses leading to

disintegration of stones.

b) Dissolved acids or atmospheric gases in rain water react with the constituent of stones causing

its disintegration.

c) Consequent increase in volume due to frost action causes the stones to disintegrate.

d) Abrasive effect of the dust particles caused by dusty winds lead to deterioration of the stones.

e) Atmospheric impurities react with stones containing carbonate of lime resulting in their

deterioration.

f) Building materials used for laying stones sometimes react chemically with the constituent of

stone, causing the stones to disintegrate.

g) Differential thermal stresses between its surface and mass may lead to fatigue which may

cause scaling and spalling.

h) If stones having different physical characteristics are used together then they may cause

mutual decay.

i) Deterioration also occurred due to roots of trees penetrating the joints of masonry thereby

keeping the stones damp which causes deterioration.

(3.3)Repairs of Stonework(3.3)Repairs of StoneworkSome form of chemical treatment may be applied to stonework to keep it dry. However it should

be noted that although the treatment may improve the impermeability of the stonework, to

moisture penetration, it can also drastically affect the appearance of the stone.

In the entire repair of stonework, attention must be paid to cracks, bulges or signs of settlement.

Accurate diagnosis is important and requires careful observations and measurements.

Repair of stone work involves one or more of the following operations:-

i) Stitching of cracks caused by structural movements

ii) Grouting of cracks not likely to worsen in condition

iii) Re-pointing of mortar joints to improve appearance, and reduce water penetration.

iv) Cutting defective stones and replacing them with compatible ones from similar sources.

v) Metal anchorages should be replaced by bronze and stainless steel ones to avoid or stop

corrosion

vi) Redressing of stonework where srcinal surface has eroded.

vii) Creepers and other plants should be removed carefully with a weed-killer which does not

have adverse effects on the stone work.

(3.3) Cleaning of Stonework(3.3) Cleaning of Stonework

Most buildings are cleaned regularly for aesthetic reasons. The choice of cleaning techniques

may depend largely on the type and condition of the surface, cost, speed and convenience to

occupants of the building. The main method commonly used as follows:-

a) Washing or Water Sprayinga) Washing or Water Spraying: This is washing away the accumulated dirt from the surface

with a water spray and brushes. It is cheap and least harmful but is also the slowest. This method

is not effective when stubborn dirt has been formed over a long period.

b) Dry-grit Blastingb) Dry-grit Blasting: Abrasive grit is blown under pressure at the surfaces to remove the dirt.

Three sizes of the nozzle are used according to the demands of the job. It could be quite dusty.

c) Wet-grit Blastingc) Wet-grit Blasting: Similar to the previous method except that water is introduced into the

air/grit stream, thereby reducing the visible dust. It is less harsh on surface, but it generates slurry

which can be troublesome.

d) Mechanical Cleaningd) Mechanical Cleaning: uses conical carborundum stones, grinding and polishing discs, and

rotary brushes attached to power tools. Special precautions and great skill is needed to avoidcausing damage. Very fast method, useful with hard stones but the cost is high.

e) Chemical Cleaninge) Chemical Cleaning: Makes use of hydro-fluoric acid as it leaves no soluble salts in the

stonework. Could be quite dangerous and caution should be taken to prevent contamination. It is

a fast method at relatively low cost for use with harder stones(Plate 10.2).

Plate 10.2. Effect of chemical cleaning on stoneworkPlate 10.2. Effect of chemical cleaning on stonework

f) Steam Cleaningf) Steam Cleaning: Uses mains water pumped to a boiler and the steam generated is played on

to the stone surface assisted by brushes and abrasive stones (Plate 10.3).

Plate 10.3. Steam cleaning machinePlate 10.3. Steam cleaning machine


1. Find out from occupants of buildings with stonework the popular methods of cleaning.

2. Analyze all the methods of stonework cleaning and recommend one for Nigeria giving our

peculiarities.

WEEK 11:- TIMBER AND TIMBER ROOF WEEK 11:- TIMBER AND TIMBER ROOF DEFECTSDEFECTS


The strength and usefulness of timber can be affected by a wide variety of defects, some of

which can occur during natural growth, others during seasoning or manufacture, while others

result from attack by fungi and insects.

(4.1) Defects in Timber(4.1) Defects in Timber

a) Natural defectsa) Natural defects occur during the growth of the tree and include the following:

i) Knotsi) Knots: parts of a branch which becomes enclosed within the growing trunk (Plate 11.1 &

11.2). They affect the strength of the timber as they cause a deviation of the grain and may leave

a hole.

ii) Shakesii) Shakes: Separation of fibres along the grain owning to stresses developing in the tree. They

affect the strength of the timber by reducing the cross-sectional area (Plate 11.3).

b) Conversion Defectsb) Conversion Defects: This is due basically to unsound practice in cutting or attempts to

economize during conversion of the timber.

Plate 11.1 Knots in a piece furniturePlate 11.1 Knots in a piece furniture

Plate 11.2 Knots on plank of timberPlate 11.2 Knots on plank of timber

Plate 11.3 Effect of shakes in timberPlate 11.3 Effect of shakes in timber

c) Seasoning Defectsc) Seasoning Defects: these defects are directly caused by the movement which occurs in timber

due to changes in moisture content. These defects are mostly irreversible.

i) Checksi) Checks: longitudinal separation of the fibres which does not extend throughout the whole

cross-section of the wood.

ii) Warpii) Warp: Distortion in converted timber which causes a departure from its srcinal (Fig

11.1).

Fig 11.1 Effect of warp in timberFig 11.1 Effect of warp in timber

iii) Collapseiii) Collapse: Condition which may occur during the early stages of seasoning when wet

timber shrinks unevenly and/or excessively(Plate 11.4).

Plate 11.4. Collapse in timberPlate 11.4. Collapse in timber

d) Fungal attackd) Fungal attack: Fungi are the chief cause of decay of timber. Their development is dependent

on moisture, oxygen and cellulose in the timber and the absence of any one of these prevents

decay. Fungal attacks can be caused by either dry rot or wet rot.

i) Dry Roti) Dry Rot: Active when particularly seasoned wood is fixed in a warm, damp and poorly

ventilated position (Plate 11.5).

Plate 11.5. Effect of dry rots in timberPlate 11.5. Effect of dry rots in timber

ii) Wet Rotii) Wet Rot: Active in timber which is excessively wet whether located in the interior or exterior

of a building (Plate 11.6).

Plate 11.6. Effect of wet rots in timberPlate 11.6. Effect of wet rots in timber

e) Insect Attacke) Insect Attack: Beetles of different kinds infect timber because the organic nature of the

material is favorable to its life cycle of hatching, growing and emerging.

f) Termite Attackf) Termite Attack: Termites are found mainly in the tropics. They are classified into two:-

i) Dry wood termites that confine themselves entirely within the timber and need no contact with

the ground. They may fly into buildings or carried there in previously infested timber

ii) Subterranean or soil termites are more widespread and need to maintain contact with the

ground. They cause destruction by constructing tubes or covered gullies in the soil over

intervening plaster or concrete.

(4.2) Defects in Timber Roofs(4.2) Defects in Timber Roofs

a) Pitched Roofsa) Pitched Roofs: Roof timbers may be affected by

i) Wet rot resulting from leaks in the roof covering or condensation.

ii) Dry rot due to confined unventilated roof spaces.

iii) Insect attack caused by power-post beetle particularly in damp conditions

iv) Construction defects caused by poor workmanship and the use of poor materials which

mostly lead to sagging.

b) Flat Roofsb) Flat Roofs: Timber and other board materials show considerable movements under changing

moisture content, thereby inducing high stresses

(4.3)Timber Roof Remedial Measures(4.3)Timber Roof Remedial Measures

Defective areas affected by fungi or insect attack may either be replaced by new ones or splicing

old to new where necessary. In case where defect is not severe, it is possible to treat the affected

timber and strengthen it with timber or steel members bolted to it. To control or reduce both

forms of attack, all timbers for roof construction should be properly and adequately treated with

preservation. Where a roof has sagged or through insufficient ties has forced walls out of plumb,

it may not be feasible to force the structure back into its srcinal position. In extreme cases

reconstruction will be necessary. Vapour barriers need to be provided to protect against water

vapour.


1. In two paragraphs each, discuss how natural and seasoning defects in timber can possibly be

reduced.

2.

Visit a timber shed and identify with the aid of pictures the defects commonly noticed in theavailable wood.

WEEK 12: PAINTING DEFECTSWEEK 12: PAINTING DEFECTS

INTRODUCTONINTRODUCTON

Paints are widely used today as a surface coating to protect, preserve and decorate many

materials such as timber, steel and plaster. Painting enhances the appearance of buildings and in

many cases also protects materials which would otherwise deteriorate. The maximum durability

of a paint is only achieved when the surface has been carefully prepared. The manner and

circumstances by which the paint is applied will also influence the performance of the paint

system. Such factors as weather conditions at the time of painting, the standard of care taken

during painting application and the actual method of applying the paint are also very important.

(4.0) Defects in Paintwork:(4.0) Defects in Paintwork:

The common defects associated with paintwork can be categorized as follows:

a) Defects Due to Poor Workmanshipa) Defects Due to Poor Workmanship:

i) Crazing and crackingCrazing and cracking: The elasticity of oil-based films diminishes as oxidation proceeds with

ageing. The loss of elasticity is caused by application of drying paint over a soft undercoat and

application over contaminated surfaces.

The effects are cracking of paint film extending through the entire paint system, crazing which

allows shallow breaks in the paint system or alligatoring which is a term used for pronounced

wide cracks over the entire surface.

Prevention includes using compatible paint systems and allowing the primer or undercoat to dry

properly/rubbing down and redecorating will remove slight crazing. In more serious cases

however, the existing paint must be stripped and the full paint system properly applied.

ii) Curtainingii) Curtaining: This defect occurs when very thick coatings fail to dry flat. The causes are

uneven application or heavy application over the wet edge. Prevention lies in the use of good

painting techniques and practice. Remedial measures include sanding down the dry film and

recoating.

iii) Grinningiii) Grinning: This is the ability of paint to hide the surface which depends on the thickness of

the film, the type of pigment used, and its absorption and reflectance characteristics. Grinning

can be due to one or more of the following reasons:

Over thinning of the paint

Applying paint too thinly or unevenly and covering too wide an area.

Pigment content of the paint is too low

Drastic colour change with too few coats

Knots in timber not properly treated.

Preventive measures involve the use of reliable materials and good workmanship in the

application.

Remedial measure is to apply more coats of paint over the entire surface evenly.

iv) Drying problemsiv) Drying problems: The paints remains soft for a long time after application which may be

caused by:

Too thick a coat being applied

Use of unsuitable thinners

Applying under wrong climate conditions

Presence of oil, grease or wax on the surface.

The remedy is to scrape off existing film, clean the surface thoroughly and the re-apply a new

coat of paint evenly. Care should be taken to ventilate the painted work.

v) Sinkagev) Sinkage: This term refers to the wet paint being absorbed into the surface which is caused by

surface porosity.

To prevent this problem, it may be necessary to apply more coats of sealer or undercoats to the

surface before the finishing coats.

vi) Painting Faults:vi) Painting Faults: Poor painting techniques or the failure to take care during the painting

process can result in other faults:

HolidaysHolidays or misses in the coating resulting from working under poor lighting conditions,

undercoat of similar colour to the top coat, or careless application.

LiftingLifting which is some disturbance of the previous coat resulting from the use of too strong

solvents for the new coat. It can also occur when previous coat is not dry when new coat is

applied. PimplingPimpling usually on a sprayed paint film, due to wrong air pressure used, paint not properly

mixed, wrong thinner used, or spraying to close or too far away from the surface.

To rectify these problems another coat can simply be applied to the surface or a complete

rubbing down or removal of paint film and repainting.

b) Defects Due to Discolouration of Paints.b) Defects Due to Discolouration of Paints.

The discolouration of a paint film can occur gradually over several months or even years. The

most common causes are:

i) Chalkingi) Chalking: This is the condition of a paint surface which, having lost most of its gloss, is

coated with a white powder. Generally, chalking appears on whites and light tints, and is the

result of photochemical breakdown of the surface layer. The main causes of chalking are:

The use of unsuitable pigments

Ageing of paint film

Repeated condensation on the film followed by drying out.

A good washing will remove the deposits and restore the gloss or colour. However, in more

serious cases, it is necessary to remove and apply the full paint system.

ii) Bleedingii) Bleeding: This is the discolouration of the paint film by some ingredient of the coating or

surface below.

The remedy is to use a specially formulated sealer or aluminium paint.

iii) Loss of glossiii) Loss of gloss: Gloss in the degree to which a painted surface reflects light. The follow are the

common causes of loss of gloss

Materials to be painted are highly absorbent, such as new plaster or wood where sealing is

essential to prevent sinkage.

Poor application of paint

Excessively rough surface

Painting in damp and foggy conditions

iv) Mould or algae growthiv) Mould or algae growth:- Paintwork affected by these organisms develop various coloured

spots, patches or stains in black, red, green or brown.

Prevention of this defect is to ensure that the surface is clean and not infested with growth priorto painting.

The remedy in mild attacks is to scrub the organisms off. In serious cases, the old paintwork is

stripped off, the wall is then treated with a fungicidal wash, allowed to dry and redecorated with

a special fungicidal paint.

c) Defects Due to Chemical Attack.c) Defects Due to Chemical Attack.

i)i) To control the problem of efflorescence it is necessary to remove all the salts by brushing and

washing, and to avoid if possible the use of water-thinned paints.

ii) Saponificationii) Saponification:- The alkalinity of lime plasters, cement rendered surfaces and concrete

results in the breakdown of oil-based paints by saponification. The degree of the breakdown

depends on the strength of the alkali present and the duration of wet conditions to maintain the

activity of the alkali.

Where the attack is severe, the film should be removed preferably by scraping, allow the surface

to dry out thoroughly and then seal the surface by the application of an alkali-resisting plaster

before repainting.

d) Defects Due to Loss of Adhesiond) Defects Due to Loss of Adhesion

i) Blisteringi) Blistering:- Blistering is due to the liquids or gasses trapped in or underneath the paint film.

This causes loss of adhesion of the paint film which with expansion, blows up the film as

blisters.

ii) Brittleness and flakingii) Brittleness and flaking;- These result from internal stresses set up in the film during the

initial contact when drying. The main causes of brittleness and flaking are:

Use of an excessively short drying oil medium.

Absorption of moisture resulting in swelling and loss of adhesion.

Painting over a loose surface

Presence of moisture on the surface will impair adhesion of the film.

The remedial measure is to completely remove all the defective paintwork and the repaint.


1. Go through the text and pick all the human factors that cause paint deterioration. Suggest

how this could be minimized.2. Observe buildings in your institution and detect paint failures. State the possible causes

and their remedial measures.

WEEK 13: DAMPNESS IN BUILDINGSWEEK 13: DAMPNESS IN BUILDINGS


Dampness is one of the most serious defects in buildings. Apart from causing deterioration by

disintegration of the structure (Plate12.2), it can also result in damage to furnishings and contents

as stains and fungal growth (Plate12.3) and can in severe cases adversely affect the health of

occupants. Good design measures are essential to keep the moisture out of building, but when

these measures are inadequate, dampness can enter the building materials to cause their

deterioration.

(4.4) Causes of Dampness(4.4) Causes of Dampness

a) Water introduced during constructiona) Water introduced during construction: During bricklaying and plastering, tones of water

are introduced into the walls. The wall remains damp until a hot season has passed.

b) Penetration of water through roofs, parapets and chimneysb) Penetration of water through roofs, parapets and chimneys: roof may admit fine rain

particularly in exposed situation. Roofs must be laid to an adequate pitch, securely fixed and

with a generous overhang at eaves to present such penetration. Parapets and chimneys can collectand deliver water to parts of the building below roof level unless they have adequate damp-proof

courses and flashings.

c) Penetration of water through wallsc) Penetration of water through walls: penetration occurs most commonly through walls

exposed to the prevailing wet wind or where evaporation is retarded. Sometimes the fault may be

from a leaking gutter or down pipe. (Plate 12.1)

Plate 12.1. Moisture penetration through wallsPlate 12.1. Moisture penetration through walls

d) Penetration of waterd) Penetration of water through broken/decayed plumbing pipes placed in walls could also

cause dampness

e) Rising dampe) Rising damp: moisture from the ground rising in a porous wall may be caused by:-

i)Absence of damp-proof courses. Fig 12.1

Fig 12.1 Absence of dpcFig 12.1 Absence of dpc

ii)Bridging of damp-proof course internally by floor screed laid which is not keyed to the

d.p.c. in the wall (Fig 12.2) or external rendering (Fig 12.3) which is liable to crack, andallow moisture to rise.

Fig Fig 12.2 12.2 solid solid floor floor bridging bridging dpc dpc Fig Fig 12.3 12.3 Bridging Bridging of of dpc dpc byby

External renderingExternal rendering

iii)Bridging by earth deposited against the outside of a wall (Fig 12.4)

Fig 12.4 Bridging by earthFig 12.4 Bridging by earth

iv)Bridging caused by mortar dropping and other debris in cavity walls (Fig 12.5)

Fig 12.5 Bridging by mortar droppingsFig 12.5 Bridging by mortar droppings

Plate Plate 12.2 12.2 disintegration disintegration of of plaster plaster Plate Plate 12.3 12.3 stains stains and and fungal fungal growthgrowth

(4.4) Remedial Measures(4.4) Remedial Measures

a) Rising dampa) Rising damp: cheap and easy measures can be taken in some instances. These include

lowering the earth or paving which extend above the damp-proof course or to remove rendering

or pointing which bridges the d.p.c. however in case of lack or defective d.p.c, more expensive

methods are adopted.

i) Physical insertion of damp-proof courses

ii) Electro-Osmotic process

iii) Installation of siphons

iv) Chemical injections

b) Rain water penetrationb) Rain water penetration: It may be necessary to rectify defective damp-proof courses around

window and door openings. A one brick thick solid wall is unlikely to withstand severe weather

conditions satisfactory and it may be necessary to apply a suitable external finish. The most

common external finish is rendering or roughcast.


1. Identify three locations in buildings that are likely to surfer from dampness, stating their

causes.

2. Suggest the most appropriate solutions to question (1) above.

WEEK14: SITE VISITWEEK14: SITE VISIT


After 13 weeks of learning the theoretical aspect of maintenance technology, it is necessary to

visit real life sites to observe practically, structures that need different forms of maintenance and

those undergoing maintenance actions.

Site visitSite visit

Students are taken to identified sites to observe various failures in buildings:

a) Foundation failures.

b) Wall defects

c) Defects in roofs

d) Dampness in buildings

e) Painting defects

Students’ ReportStudents’ Report

Students are expected to write a comprehensive report on their observations to cover:

• Causes of defects

• Picture/sketches of observed defects

• Schedule of dilapidation

• Recommendation towards preventing future occurrences.

The report will take the following format:-

• Preliminaries

• Main report- background

- Case study

- Analysis

• Conclusion

The format of the schedule of dilapidation is shown below

SCHEDULE OF DILAPIDATION

LOCATION OF PROPERTY:

DATE OF INSPECTION:

INSPECTED BY:

S/no Component Defect Remedies Bill item description Qty Unit Rate Amount

Fig 5.1 Format of schedule of dilapidationFig 5.1 Format of schedule of dilapidation

WEEK 15: TECHNOLOGY OF WEEK 15: TECHNOLOGY OF MAINTENANCEMAINTENANCE


The technology of maintenance is concerned with all the factors that influence and cause the

need for maintenance work.

(4.6) Technology of Maintenance(4.6) Technology of Maintenance

Occurrence of defects in the fabric of a building can result from many unrelated decision and

action. In order to understand technology of maintenance, the following must be discussed:-

a)Design decision

b)Maintenance at design stage

c) Materials

d)Assessment of exposure

e)Climate

f)Atmospheric pollution

g)Durability

(4.6) Terotechnology(4.6) Terotechnology

The term ‘’terotechnology’’ has been used to embrace the life cycle requirements of physical

assets. It is a combination of management, financial engineering and other practices applied to

physical assets in pursuit of economic life cycle costs. It is concerned with the:-

a) Specification and design for reliability

b) Ease of maintenance of plant, machinery, equipment, building and structure with their

installations.

c) Commissioning

d) Modification and replacement

e) Feed back.

The standard of maintenance achieved has an important influence on the quality of the built

environment and there seem little doubt that society will continue to expect higher standards in

new and existing buildings. There is a need to improve the methods of managing and executing

building maintenance. Maintenance budgets should be clear and well reasoned and supported by

full information. Feedback from occupier to designer should be improved in order to assemble

information on both the preference of the user, and the performance of materials, components

and constructional methods. There is a general lack of essential basic data. Design teams

frequently neglect consideration of maintenance aspects and there is a great need to reduce the

gap between design and maintenance. Decision making in building maintenance could be

assisted by the application of operational research techniques. Consequently for many years to

come, maintenance will remain a significant and important part of the work of the construction

industry.

(4.6) Role of Maintenance(4.6) Role of Maintenance

The performance of any building can be affected by decisions taken and actions performed at

any stage of a building project, from its initial conception to its final demolition. This reflects the

importance of maintenance throughout the life of a building. A skilful design can reduce the

amount of maintenance and also make it easier to carry out the work. Decisions at the design

stage include selection of materials, forms of construction, orientation of the building and user

requirements.

The construction stage requires a high level of supervision to ensure good standards of materials

and workmanship as well as correct detailing and specification.

Maintenance is needed throughout the entire period that the building remains in use or

occupation so that the various facilities are kept to an acceptable standard. The amount of

necessary building maintenance work could be reduced by improved methods of designs,

specification and construction. Effective maintenance management embraces many skills. These

include the technical knowledge and experience necessary to identify maintenance needs and to

specify the right remedies, an understanding of modern techniques of management, knowledge

of property and contract law, and an appreciation of sociology.


1. Briefly explain seven considerations the designer must take to minimize maintenance at the

design stage in two pages.

2. On a page discuss the importance of maintenance throughout the life of a building.

MAINTENANCE TECHNOLOGY...Building maintenance technology essentially deals with the study of the occurrence of building defects and the remedies which such defects would require. The

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