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BUILDING   MAINTENANCE

by

Dr. A. Ghafar Ahmad

Scraping and blow-torch techniques to remove stubborn paint on ceiling

In the practice of building conservation, historic buildings are not only recorded for historical and structural purposes but for the programming and future work of building maintenance. All elements of historic buildings tend to detoriate but at a greater or lesser rate depending upon function and location. Buildings will rapidly decay and degrade when building maintenance has been neglected. This can, of course lead to other harmful effects and threaten safety of both occupants and building finishes. It is very important for property owners to provide and programme appropriate maintenance work for their historic buildings.

Building maintenance is actually a process by which a building is kept usable at a pre-determined standard for the use and benefit of its occupants or users. The standard may vary according to the function of a building. Building maintenance has become a major part of the work in the building industry and absorbs milllions of Ringgit each year. Maintenance practically begins the day a builder leaves the building site. Design, materials, workmanship, function, use and their interrelationships, will determine the amount the maintenance required during the lifetime of a building. The prime aim of the building maintenance is to preserve a building in its initial state, as far as practicable while retaining, where appropriate, its investment values, and presenting a good appearance; so that it effectively serves its purpose.

It is impossible to produce buildings which are maintenance-free, but maintenance work can be minimized by good design and proper workmanship carried out by skilled experts or competent craftsmen using suitable codes of installation, requisite building materials and methods. The importance of maintenance is such that it requires a properly educated and trained workforce involving good management as well as suitably trained craftsmen.

Building maintenance requires trained and experienced workforce

Common building problems have been discussed in Paper 2. The main purpose of this subsequent paper is to discuss methods and techniques associated with building repair in an attempt to overcome such common building problems. In addition, it also highlights cyclical maintenance programmes and principles of repair.

2.0 Cyclical Maintenance Programmes

Building maintenance should be organized through a rigourous programme of cyclical maintenance starting with daily routines and working upwards which involves periodic programmes of daily, weekly, monthly, semi-annual, annual inspections; and quinquennial routines. For the quinquennial routines, it is the responsibility of architect or surveyor to inspect any structural defects. The long-term maintenance plan should be revised and updated after each inspection. Any attention to the building defects should also be studied for the next report presented to local authority. Some of the tasks that the architect or the surveyor should look in the inspection are cleaning out all void and spaces, changing tap washers, checking lighting conductors, inspecting and testing electric installation, checking any sign of abnormal deterioration; and cleaning out gutters of leaves, branches or plants.

However, some inspections are carried out at least every thirty years, especially for major monuments. In such a case, a report containing information of updated maintenance and repair work, photographs, key drawings and recommendations should be prepared by a qualified professional. This is to ensure that the report will be a valuable source of reference for those responsible for a building now and in the future.

Depending on the nature work of maintenance and repairs, the programme of cyclical maintenance may be divided into two main categories: day-to-day maintenance and maintenance involving builder's works. As stated by the English Heritage of the United Kingdom, the day-to-day maintenance include work which can be dealt by building owner without the need to employ outside labour. This consists of cleaning leaves from gutters, down pipes and drainage channels; removing plant growth from masonry, looking for insect and termite attack in timber, checking ventilation; and removing bird droppings. In addition, Sir Bernard M. Feilden, a leading British conservation expert, has suggested that fire-detection systems should also be checked as well as windows, doors, lavatories and electrical system. It is advisable to ask cleaners to report any defects they note such as broken windows, leaks in roof, falling pieces of masonry and lime dust from spalling plaster or insect droppings. The second category, which is maintenance involving builder's works, is best carried out on an annual basis by a builder who has knowledge of and sympathy towards the construction of historic buildings. Such works include refixing and replacing loose or broken roof tiles, eaves, gutters, down pipes; and rodding and inspection of soil drainage systems. Besides, testing all fire extinguishers and refilling if necessary, cleaning out ducts and air-conditioning units, servicing elevators; and decorating and cleaning sections of the building interior are all needed in the building maintenance.

However, to secure the general structural stability and life of a building, it is important to regularly inspect not only the main structural elements including foundations, walls and roofs; but other common building problems. Proper methods and techniques of building repairs; and good maintenance programmes are equally important. It is a duty of owners, conservationists, architects, trustees, local authorities and the public to see that an historic building is handed on to the next generation in good condition.

There is no standard specification for the repair of historic buildings nor should there be! However, the English Heritage has listed ten main principles of repair, restoration and maintenance of historic buildings; which can be a basic guidance for the conservation of historic buildings and monuments in Malaysia. The principles are broad and generally applicable to the whole of the built environment. It should be recognised that each individual case must be analysed so that the principles can be applied to generate specific solutions for particular problems.

Determining the primary purpose of repair is the most important principle. Its main objective is to prevent the process of decay of building materials and characters while maintaining building structures in good condition. It is also important not to alter any features that give the building its particular historical or architectural significance.

The main need for repair is to achieve a sufficiently sound structure, particularly to ensure structural safety and therefore its long-term survival and to meet certain requirements of any appropriate use. Therefore, any intervention during repair must be kept to the minimum in order to stabilise and conserve historic buildings.

Any unnecessary replacement of historic fabric should be avoided even though the work is carefully carried out. This is to prevent any adverse effect on the appearance of a building which then significantly reduces its historical or architectural value or seriously diminishes its authenticity.

Before any repair is carried out, it is necessary to analyse thoroughly the historic development of a building. This is to ensure that any historical facts about the buildings are well documented for future work or research. Archaeological and architectural investigation, recording and interpretation of a particular structure, and its assessment in a wider historic context may be desirable. If appropriate, these processes may continue even during the course of repair.

Any decayed fabric should be analysed prior to carrying out the work of repair and replacement. This include an analysis of causes of defects, condition and nature of existing building materials; and a survey of structural defects. The main purpose of carrying out such analyses is to avoid any repetition of building problems or to repeat previous design errors.

In order to preserve the appearance and historic integrity of a building and to ensure that repairs have an appropriate life, all repair work should match existing materials and methods of construction. Therefore, any new methods and techniques of repair should only be carried out where they have proved themselves over a long period and also where traditional alternatives cannot be identified. However, the degree of damage caused to the building's appearance, historic integrity and fabric should be considered when it is decided to adopt new methods and techniques.

In carrying out repairs for building materials, it is important to execute the work honestly. There should be sincerity to the materials and also the whole building as well. However, repairs should be dated discreetly where appropriate.

In some cases, additions or alterations are of importance for the part they play in the cummulative history of a building. In fact, there will often be a strong presumption in favour of their retention. However, if they are to be removed based on the grounds of having no intrinsic value in themselves or may seriously disrupt the overall architectural interest of the building, then the implications of doing so must be carefully considered in advance.

Some elements of an historic building, for example balustrades, pinnacles, cornices, festoons or window tracery, may have been broken or lost in the past. If they are of structural significance, then they should be restored or replaced in the course of repair. However, to avoid inaccurate and unnecessary replacement, sufficient evidence should be provided to support both the existence and form of the lost features.

Like other historical objects, buildings of architectural and historical significance should be regularly monitored and maintained. Reviews should include public safety and access, protection of historic buildings from traffic, fire and security; and preventive maintenance. Choosing an appropriate and sympathetic use for an historic building is important to secure its future and also to minimise its repair requirements and the need for structural interventions.

My second paper entitled "Common Problems of Historic Buildings" has identified twelve common building problems and explained two major aspects which are causes to such problems and factors that govern building defects. This paper, however; concentrates mainly on the methods and techniques of building maintenance which can be applied to counter the problems. The twelve common building problems include fungal stain or harmful growth, erosion of mortar joints, peeling paint, poor installation of air-conditioning units, defective plastered rendering, cracking of walls or leaning walls, defective rainwater goods, decayed floorboards, insect or termite attacks, roof defects, dampness penetration through walls; and finally unstable foundations.

For fungal stain or mould on wall surfaces, the problem can be handled by low pressure washing. Water spray, at low pressure, is used to soften fungal stain or mould on the wall surfaces. Then, bristle brushes are applied to remove the stain. Chemical products containing caustic soda should not be used because they contain soluble salts which likely can cause serious damage to walls, particularly of stone. Instead, a chemical cleaner such as hydrofluoric acid is recommended, for it leaves no soluble salts in masonry. If there are open joints or holes in the masonry walls, it is important to avoid the water from penetrating through the structures. This is because it may cause decay in other building materials such as timber and iron fixing.

Harmful growth should be removed from the walls surfaces as quickly as possible. This is due to the fact that the roots can go deep into the existing holes causing further cracks and water penetration. Removal of harmful growth can be done by cutting the thick roots and applying an ammonium sulphamate paste on the root. This will gradually wither and kill the plants. Once the plants are drying out or shrinking, they can be removed by carefully pulling them out from the walls.

Erosion of mortar joints occurs once there is a presence of salt crystalization, scouring action of winds, disintegrating effects of plant growing on wall or water penetration leading to the concentrations of moisture and dampness. Where mortar has weathered out or become soft and crumbly, repointing should be undertaken which is an operation of raking out decayed mortar from the joints of masonry or brickwork to a depth of between 25mm and 40mm (or at least to twice the height of the joint); and refilling the joint with suitable mortar. Decayed mortar can be removed forcibly by the use of a mechanical disc or carefully raked out by using a knife or spike manually. Many historic buildings used lime-based mortar for the bedding. In such a case, repointing should be carried out using a lime-sand mortar in a proportion of 1:3. For the mixing of a new mortar, it is advisable to match it in mix and finish with the original mortar. In addition, sound old pointing or mortar joints should be left undisturbed.

In many old buildings, there are layers of paints being applied on walls, mainly of plaster. Paint, depending on the nature, condition and type; can be removed by six main methods. However, before choosing any appropriate method of paint removal, it is important to analyse the surface of damaged paints and possible side effects to other building materials. Consultations with various paint manufacturers are essential and helpful. The six main methods of removing paint are discussed as follows:

The method is a process in which steam at low pressure is applied to the paint through a hose capped with a perforated metal concentrator. The appliance used is similar to that of stripping wallpaper. It is useful for removing water-thinned paints including the emulsions because the combination of heat and moisture from the steam can soften the paint which is removed with a sponge and water. Steam stripping is more effective and can be faster over large areas compared to water washing.

4.3.3 Chemical Paint Removers

There are two main types of chemical paint removers: solvent (non caustic) and alkaline (caustic). Both of which contain toxic ingredients which are flammable and health risk; and that the method should be handled by a competent and experienced person. Application of the removers should be with a brush and when appropriate, should be used in well-ventilated rooms. The solvent remover, usually based on methylene chloride, are very effective in removing only oil-based paints. The alkaline remover is not only used on the oil-based paint but other tough paints that cannot be removed by other means. Once the chemical paint removers are applied, the paint layers are softened. The use of hard brush and water is helpful in scrapping or scrubbing off the softened paint. These removers are not suitable for plywood, veneers or hardwood. They can also be harmful to brickwork, stonework and metal.

4.3.4 Abrasive Methods

Paints can be removed by hand scrapping, sanding and mechanical methods. For the hand scrapping and sanding, a wetted medium-coarse glass paper wrapped round a wood block is used, particularly in removing a thin layer of paint. However, the mechanical method uses hand-powered tools applied with standing attachment such a disc, flap wheel or rotary stripper. It is practically suitable for flat surfaces, mainly to remove multiple layers of old paintwork. Blast cleaning by using controlled pressure of air or water is helpful in the abrasive methods.

4.3.5 Hot Air Paint Stripper

Hot air paint stripper, an electrical tool with heat adjustable, is basically designed to soften and blister oil-based paints and varnishes on wood surfaces before the paints are scrapped away with a stripping knife or scraper. The method is fast and effective but is not suitable for the removal of water-based paints or any type of paint on metal or plaster.

4.3.6 Burning Off Method

Like the hot air paint stripper, the burning off method is effective on oil-based paints but not on water-based coatings. Instead or hot air, blowlamps or blowtorches are used to soften the paint prior to any scraping. The work should be handled by an expert who is accustomed to the devices; or otherwise the paint may catch fire which is a danger to other building materials.

4.4 Poor Installation of Air-Conditioning Units

There are several aspects which should be considered before installing any air-conditioning units including the amount of energy, running costs and maintenance needed, possibilities of causing structural disturbances to existing walls and ceilings, and the appearance of the buildings, particularly if the units are placed on front facades. In addition, such considerations should first look upon the three main factors which are as follows:

4.4.1 Natural Verses Artificial Ventilation

In responds to the local climatic conditions, most of the historic buildings in Malaysia were designed with vernacular elements such as louvered windows, full-length windows or French windows, fanlights, air-wells, high ceilings and internal courtyards. These elements play a major role in encouraging natural ventilation, giving buildings and occupants a cooling effect. Buildings located near the sea may have an advantage because a great amount of winds received is good for either stack-ventilation or cross-movement of air.

If an historic building is converted to either a museum or library, then there is a need to have air-conditioning systems, particularly in controlling the internal humidity and temperatures. An air-conditioning system may also be beneficial for old buildings situated in an unfavourable environment of dust, dirt and sulphur dioxide. Furthermore, office buildings and banks require air-conditioning systems, for the users or occupants spend long hours working in the buildings. In such a case, dependence on natural ventilation alone is not sufficient because the users or occupants may feel uncomfortable when working in a warm and humid environment.

4.4.2 Placement of Air-Conditioning System

When it is decided to install an air-conditioning system into an old building, it is important to place its units so that they do not destroy or degrade building materials and affect the appearance of the building. There are two common types of air-conditioning systems found in many historic buildings in Malaysia which are a domestic-scale packaged system and a split system. The former, commonly placed on window units or walls, has all components: compressor, condenser, evaporator and fan in one unit. It normally serves one room, without any ducts. The latter, however, has the compressor and condenser placed outside while the evaporator and its fan are inside the building.

Where a split system is installed, it is important to place the compressor and condenser units on ground level at the back of a building or other suitable location. If the units are placed on the ground level and not to be visible, it is of a good idea to put screening devices such as short plants, shrubs or fences around the units. Any ducts should not run in full view but placed above a suspended ceiling. However, it the suspended ceiling reduces the room height and also causes other problems to the building structures and fabric, then it is advisable to leave the duct visible. For the ducts on upper floor, they can be concealed conveniently in a roof space. A new chiller plant room, if necessary, may be constructed outside the building to protect the compressor and condenser units. For the domestic-scale packaged system, the placement can be in a corridor, balcony or verandah, in the conditioned space in itself but not on window units or fixed onto walls. To match and blend with the existing colour of a building, the air-conditioning units and electrical wirings may be painted.

4.4.3 Maintenance of Air-Conditioning System

Since most air-conditioning systems consist of a fan, filter and cooling coil, a regularly check-up or maintenance is desirable. Most of the maintenance works depend on both the types of filter used in the system and the extent of pollution in the environment. As a rough guide, if the system uses filter cells, then they may have to be changed or cleaned once a month in heavily polluted locations, once every two months in city centres and once in every three months in rural or suburban areas. However, for the cleanable filter the need to change or clean the part is about one to two years. Other maintenance works include a check-up of blocked filters resulting in reduced air flow and breakdown of fan bearing causing downflow of cold air with consequent occupancy discomfort, cleaning out ducts and overhaul of the air-conditioning plant at least once a year. A checklist should be prepared and accompanied during maintenance visits. It is also important in old buildings to provide easy access for building maintenance and inspection.

4.5 Defective Plastered Rendering

Before any repair is carried out, it is necessary to analyse the broken plaster, particularly its original colour, texture and its major ingredients including, if any, the presence of calcium carbonate (lime) with gypsum, marble dust, ground brick or sand as fillers; and animal hairs or vegetable fibres. This is to ensure that the old plaster can be copied and matched. Thickness of the plaster should be checked to avoid any uneven finish coats. Thoroughly cleaning is essential and every trace of dust should be removed.

For the repair of the broken plaster, the main principle is such that the new plaster must be no stronger than the material to which it is applied. This is to allow sufficient flexibility to accommodate any movement of substrate and also to allow moisture to evaporate freely from it. Wetting the existing coats before the application of the new plaster it important to reduce the development of suctions. Careful stripping and cutting the broken plaster should be done without affecting the existing sound plaster.

Depending on the texture of the plaster wall, column or ceiling, a new mixture of one part of lime to two of sand can be applied in one coat of about 6mm - 10mm thick. The choice of sand, however, relies upon the proposed texture of either the external or internal work. For example, coarse sharp sand are generally preferred for external work while soft sand for internal work.

For the plaster ceiling, if it is loosened; a technique of reattachment can be applied. The process, which requires the drilling of 5mm holes through the ceiling lath at 300mm centres, uses consolidant injected into the holes. In a case where floorboards cannot be lifted, holes may have to be drilled through the plaster itself. Both the lath and plaster need to be wetted with a mixture 3:3:2 parts of water, denatured ethyl alcohol and acrylic emulsion by using a foaming spray. The acrylic emulsion acts as a bonding agent in the mixture. For the restoration of a decorative plasterwork, a specialist firm with a knowledge of making moulds of cornices and ceiling using silastomer silicone rubber should be consulted.

 

4.6 Cracking of Walls or Leaning Walls

If the cracks are fine and confined to mortar joints, then it is sufficient to rake out the front portion of the mortar joint and repoint. The use of two strong mortar and rich in cement should be avoided. For diagonal cracks which often being widest at the foundations and may terminate at the corner of a building, they often occur when shallow foundations are laid on shrinkable sub-soil that is drier than normal or when there is a physical uplifting action of main roots of a large tree close to the walls. Unless the walls have become structurally unsafe, it may not be worth of clearing off the tree and repairing the walls. If the walls need to be repaired, allowance must be made for any further growth in the roots by bridging the foundations across them.

For a leaning wall, raking shores may be used to provide temporary support. Depending on the height of a building, the shores either made from timber or steel are placed against scaffold boards connected into the outward wall with timber needle. Cross bracing and steel stakes or hardwood wedges are needed to give a greater support to the shores. With tall buildings, the number of shores or rakers depends on the number of floor joists. Angled at between 45 and 75 degrees, the centre line of each shore intersects the ends of the floor joists and centre lines of wall plate to give maximum support at critical points of concentrated loads. To avoid any structural collapse due to the absence of adequate shoring, building engineers and builders should be consulted for detailed advice.

Other major repairs for the leaning walls, particularly of brickwork include methods of providing a restraint to walls which are strapping a connection into wall, providing reinforced concrete; and inserting a tie plate connection through walls. When deciding to adopt the method of the tie plate connection through walls, it is essential to consider how much the plate may affect the building appearance. These methods of repair are normally applied to bigger buildings and tend to be permanent.

4.7 Defective Rainwater Goods

Examples of defective rainwater goods are sagging or missing eaves gutters, corroded or broken galvanized iron down pipes; leaking rainwater heads and undersized gutters or down pipes which cause overflow of water. In renewing or repairing the defective rainwater goods, it is important to maintain a proper system of disposing water from eaves gutters to open channels or drains at ground level. It is also essential to consider the future maintenance of the goods. In regard to the iron down pipes, it is important to fix them on spacers two or more inches clear of the wall. This is to ensure that any leaking will tend to run down the pipe rather than the wall. As a result, water penetration into wall can be prevented. When the down pipes are fixed in this way, rainwater heads should be painted to inhibit the development of rust. However, this is not so with the lead down pipes, nor lead rainwater heads and gutters. Any splits found in these goods should be fixed by lead welding, not soldering. For undersized gutters or down pipes which unable to cope with the heavy rain, then it is advisable to fit larger components of the same design; and not so much larger that they affect the appearance of the building. All rainwater goods should be clear from any blockage including the harmful growth. Weekly inspections on the gutters and down pipes are essential.

 

4.8 Decayed Floorboards

Proper maintenance and repair of the decayed floorboards are very important. Decayed floorboards can be repaired or patched by a number of ways depending on the nature of the decays and whether or not they may disturb the building structures. The main principle in repairing or patching a decayed floorboard is that although a board may be suffering from the decay, its strength may not have been reduced significantly. Therefore, only the affected area should be repaired or patched and not necessarily the whole floorboard. Following steps show the proper methods and techniques of repairing or patching old floorboards:

4.8.1 Lifting Floorboards

In the process of lifting decayed floorboards; ingenuity, preparation, care and patience are the keys to success. The necessary tools needed include a 6 inch bolster, wooden blocks of various thickness, a flat hardened steel plate, a hammer, a 1/2 inch batten about 8 inches longer that the width of the board, nail punches, a hacksaw; and a crowbar. There are two stages in the process of lifting the floorboards. The first stage, which is easing up the first board, requires gaps big enough for the bolster to fit between boards. Using a block of wood or flat hardened steel plate placed at the edge of the adjoining board, the bolster fits the gaps, works on one side of the decayed floorboard; and levers from side to side to loosen it. Repeat the same procedure on the other side of the board until the board has raised by up to one third of its thickness. Then, move towards the middle and back towards the end until one end of the board comes free. The second stage is the method of lifting subsequent boards by using a block placed across the joist; and a crowbar inserted between the board and joist, levering upwards. Where the board is very weak, placing a block underside of board or clamping in position is essential.

4.8.2 Reducing Unevenness in a Warped or Twisted Board

Sometimes a floorboard may warp or twist due to uneven shrinkage or expansion. It is impossible to make a warped or twisted board perfectly straight but the condition can be reduced to an acceptable level. Lift the warped or twisted board using the method above, and immerse and soak in water. Then, lay the board out to dry on battens and apply weights to overcome twisting. If the board tends to revert to its original twist when weights are removed, this should be compensated for by over weighting. Leave the board under pressure for at least one week and allow it to dry slowly. If it is held flat while drying then the warping is likely to be reduced. Before relaying the board, it is necessary to treat the underside of board against insect or termite attack.

4.8.3 Repairing a Split Board

A split board with a crack in the middle can be treated by first lifting it and then, placing on two clamps using small blocks to protect edges of board. Prior to this, the board should be marked on the underside for the positions of joist, crack should be cleaned; and if necessary, any warp or twist should be removed. A small block of same board with grain running in same direction is needed, placed on top of the split and screwed to underside. Then, relay the board.

4.8.4 Repair a Broken Edge

To repair a broken edge, cut out around the broken edge of a lifted old floorboard and mark joist positions on underside of the board. Select seasoned timber of the same variety with the grain running in same direction and form new section to fit the old. Glue together and cramp in position. If the broken edge occurs between joists, the new section can be supported by block screwed to underside of board. Relay the board after work is finished.

4.8.5 Strengthening a Weak Board

A weak board can be strengthened by screwing battens to sides of joists and then laying 25mm thick slats on battens under the weakened board. Before relaying the board to its position, treatment of board and batten against insect or termite attack is essential. In relaying old boards, lightly greased brass screws (iron screws will eventually rust and extremely difficult to remove) should be used for nailing the floorboards down. This is important, particularly to avoid any disturbance over a decorative plaster ceiling underneath; and also where frequently lifting and relaying of the board will be necessary. It is also important not to sand the old board, for it will remove the smooth surface of the board. Polishing boards is acceptable but applications of modern varnishes and finishes should be avoided because they tend to give an unsympathetic appearance.

4.9 Insect or Termite Attacks

Insect or termite attacks usually happen in digestible timber structures located in damp and moist areas. Common areas where insect or termite attacks usually occur include timber wall plates, the feet of rafters and bearing ends of beams and trusses; and in all timbers which are placed against or built into damp walling. Timber structures found with many insect or termite holes are dangerous because they may soften the timber and form further cracks. Eventually, the timber loses its load bearing capacity and fails. For the insect or termite attacks, affected timber can be treated by pressure-spraying with insecticide or fumigant insecticidal processes. Timber can be preserved by chemical process either before or after manufacture. The chemical process is basically done by applying solutions using brush or spray on timber surfaces. There are several types of timber preservation including creosote, water-borne solutions of copper, chromium and arsenic chemicals; organic solvent solutions (mixtures of fungicides and insecticides); and appropriate chemicals for flame-proof protection and water-repellency to timber. Care must be taken to avoid environmental pollution and to use preventive materials in a controlled and appropriate way. However, prevention by natural ventilation is to be preferred to the use of chemical preservatives. All infected timbers should be taken out and burnt immediately.

4.10 Roof Defects

Before carrying out regular building inspections and determining the method of repairs, it is important to understand common roof defects. In Malaysia, clay tiles have been widely used in many historic buildings. They appear in different sizes and colours usually reddish, depending on the manufacturer that produced them. Some of the historic buildings still have the original tiles even though their conditions need to considered. Others have changed to a more modern type of roof coverings including corrugated sheet metal or weather proof tiles. In examining the conditions of the roof tiles, it is important to check the following items:

· the fixings holding the roof tiles to the roof structure

· the joints in the roof tiles

· inaccessible and unattended points, particularly internal valleys and gutters

· points of maximum exposure such as at the foot of a rainwater pipe

· abutments against other structures such as jack roof, chimney or finial

It is advisable to take photographs of the roof tiles prior to any recovering, repair or stripping. This is to ensure that the original tiles are properly copied or followed, as be a reference to the new or second-hand tiles. When stripping, it should be carried out carefully so that all sound existing tiles remain undamaged. They may be sorted according to type, size and thickness; and stored ready for reuse. Replacement of decayed battens should preferably be of good quality soft wood pre-tested against insect or termite attacks. This is because the durability of the battens is important in the life of the whole roof. As galvanised steel has shorter life, the use of stainless steel nails is preferable for fixing the tiles to the rafters, although they may be difficult to remove when repairs are necessary. When tiles get displaced, they should be renailed if possible.

Retiling should be carried out by using tiles salvaged from the roof or sound second-hand tiles that match the existing ones in type, size, thickness, colour and texture. Mixing the tiles judiciously is quite important to maintain or get back the original composition of colour and texture of the entire roofs. It may be necessary to have purpose-made tiles made to match existing ones.

4.11 Dampness Penetration Through Walls

Dampness may enter a building from the ground though it should have been prevented from doing so by properly constructed damp-proof courses and membranes. Moisture present in the ground may penetrate though cracks or mortar joints in the wall. Lack and failure of the damp-proof course can also cause dampness to rise up walls. Providing that there is no damp-proof course in a building, there are several ways that can be introduced to prevent dampness from penetrating walls. The first method is the insertion of a damp-proof membrane in a stable wall of not more that 450mm thick. This can be done by sawing a slot in a mortar bed joint, normally just above the floor slab and at least 150mm above outside ground level; and then inserting the membrane in the slot in 600mm lengths.

Alternatively, the damp-proof courses can be inserted by the method off electro-osmosis damp-proofing. The installation consists of 25mm holes drilled from the outside with strip electrodes of high conductivity copper mortared into drillings and looped into copper strip set into bed joints at damp-course level along the wall face. The purpose is to provide a bridge between a wall at the damp-course level and the soil, thus destroying the surface tension and also preventing rising moisture.

Another process of preventing the rising damp is by injecting a siliconate solution in water or a siliconate-latex mixture into the lowest accessible mortar bed joint through drill holes 10mm in diameter at 50mm intervals. The siliconate, which becomes a water-repellent bond after injection, acts as a stabiliser within the wall allowing the area to harden off. The method is useful especially for thick or unstable walls where damp-proof course insertion may not prove possible.

4.12 Unstable Foundations

The most traditional method of repair to unstable foundations is underpinning. It may be used to form deeper or wider foundations but it relies on adjacent excavations which need to be shored and extensive enough to allow access for concreting. In other words, short lengths of walling are cut out and propped up while the large foundations are inserted. Underpinning comes in different forms including:

· continuous underpinning

· closely spaced piers with foundation arching

· continuous beam and piers

· headed lintel and pier

· bored mini-pile through footing

· bored micropile with caps

· bored pile with cantilever cap

· bored pile with case steel needles

It is important to carefully arrange the phasing of underpinning, for such work involves shifting load from one part of the structure to another. In addition, the success of underpinning depends on the strength of the masonry above and if this is unsound, further difficulties may occur. It is an opportunity to insert a damp-proof course when underpinning the foundations.

Most of the historic buildings were built long before the increase of the traffic vibration environment. In order to eliminate the source of the vibration, it is important to detour the traffic going to the areas where they are important or large numbers of historic buildings. Local authorities and town planners should play a major role in banning heavy vehicle and restricting vehicle speeds in such area. Road surfaces near historic buildings should also be carefully maintained.

Another way of protecting historic buildings from traffic vibrations is through the insertion of vertical curtains of thixotropic grout in trenches to insulate the foundations of buildings. The method, which was suggested by the Building Research Establishment of the United Kingdom, requires the trenches to be at least equal in depth to one-third (1/3) of the wavelength of the vibration concerned. However, for low frequencies, depending on the velocity of the wave propagation in the soil, the depth can exceed 5m or 16 feet. It is important to carry out a site investigation using soil mechanic techniques prior to the insertion of the trenches.

For historic buildings located close to the road, there is always a possibility of direct impact from a heavy vehicle. Where the traffic cannot be banned or restricted from the road, a traffic barrier should be fixed directly to a building in a form a steel box beam with collapsible hexagon mounting brackets. Alternatively, free-standing barriers can be placed with a minimum clearance of 300mm between post and the building with a set-back of 600mm from the kerb.

5.0 Conclusions

As the practice of building conservation involves a wide scope of work including building repair and maintenance, a person responsible for keeping the historic buildings in good condition should not only understand the causes to building defects but also other aspects of building repair and maintenance. Such aspects of building repair and maintenance are as follows:

· importance of building repair and maintenance

· nature of building repair and maintenance

- servicing (routine cleaning operations)

- rectification work ( to overcome problems in design, inherent faults in or

unsuitability of components, damage of goods in transit or installation and

incorrect assembly)

- replacement (of building materials with the ones of better quality and standard)

· research into building repair and maintenance

· lives of buildings (depend on social structure and economic conditions)

· technology of building repair and maintenance (factors that influence and cause the need for maintenance work)

· expenses incurred in building repair and maintenance

Building repair and maintenance also require sufficient supervision of a competent person to ensure that the work is carried out to a satisfactory standard and in accord with the agreed specifications. All works or repair and maintenance should be recorded, photographed and documented for archival purposes and future building maintenance.

The situation in Malaysia is such that most of the works involving building repair and maintenance unfortunately have failed to observe the principles of repair and disregard proper methods and techniques of building maintenance. It is the main purpose of this paper to highlight the importance of such matters. Examples given in this paper represent a general picture of common building problems and their solutions. However, it is important to emphasize that each building problem should be handled individually following a thorough study of the building structures and conditions.

 

References:

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Construction Industry Research and Information Association (CIRIA), (1986), Structural Renovation of Traditional Buildings, London: CIRIA. Report III.

Eldridge, H.J.,(1976), Common Defects in Buildings, London: Her Majesty's Stationary Office (HMSO)

Feilden, B.M., (1982), Conservation of Historic Buildings, London: Butterworth Scientific.

Hughes, P., (1988), Patching Old Floorboards: Information Sheet 10, London: Society for the Protection of Ancient Buildings (SPAB).

Insall, D.W., (1975), The Care of Old Buildings Today, London: Architectural Press Ltd.

Seeley, I.H., (1976), Building Maintenance, London: MacMillan Press Ltd.

Tack, C.H., (1979), Preservation of Timber for Tropical Building, Watford: HMSO.

Wingate, M., (1987), An Introduction to Building Limes: Information Sheet 9, London: SPAB.

Wright, A., (1989), Removing Paint from Old Building: Information Sheet 5, London: SPAB.