PREVENTIVE MEASURES AND MAINTENANCE OF BUILDINGS | LCETED | SITE ENGINEER

 

Primarily it is needed to take preventive measures wherever feasible before facing any failure on a small or large scale. A small investment or preventive measure is taken at the initial stage not only prevents failure but also gives a long life of the building.

Then maintenance plays a major role to make every component of a building function properly and at the same time increases the lifespan of the building.

Maintenance of floors, doors and windows, sanitary appliances, water supply, drainage system and electrical system are all important.

Further, checking of leakages, identifying the causes of cracks and repairing them or make some preventive measures to avoid such fractures in future. Special repairs, if any, are to be attended to then and there. Apart from the routine maintenance annual general maintenance of a building should be made and implemented.

 

MAINTENANCE OF FLOORINGS

As there are many types of floors constructed, maintenance of some of the important floors are dealt with below.

 

Terrazzo Floors

Cleaning of terrazzo floors with water may be taken up after 3 months of laying. After this period, it should be swabbed daily using clean water and a clean rough swab (floor cloth) which should be rinsed in water frequently so as to avoid dirt being back onto the floor. The floor is then allowed to dry in the air. After this initial cleaning, ordinary swabbing shall keep the floor shining.

Sometimes acid polishing of terrazzo floors is resorted to after machine polishing during the first laying of the floor. If need be, this can be repeated. Oxalic acid is used for acid cleaning. After acid polishing, the following day the floor is wiped with a moist rag and washed clean with water.

 

Marble Floors

For marble floors, daily maintenance is to be made. This is carried out by mopping with a mild detergent in water. Marble gets easily stained and scarred. If there is a spill on the floor, it should be cleaned immediately.

Stubborn stains should be removed based on the type. If the stain is from grease, a paste of chalk dust or whiting with acetone. This mixture is applied on the stain and allowed to stand overnight. The mixture is sponged off and the treated area is buffed. If the stain is from any organic source like tea, fruit juice, etc., chalk powder with hydrogen peroxide mixture is used. This paste can also remove stains due to rust. Such stains can also be removed by dry borax and damp cloth followed by warm water rinsing.

 

Linoleum Floors

For this floor mopping with kerosene oil can pick up all the dirt. After the removal of dirt, the floor may be wiped with water and mopped well to set a polished surface.

 

Concrete Floors

A properly constructed concrete floor should be dust-free under normal use. Dusts in floors can be reduced by the application of a hardener, or by waxing, or by painting it with a solution of oil spirit. For such application, raw or boiled linseed oil mixed with an equal amount of turpentine has been found to be effective. Painting with epoxy, acrylic or chlorinated rubber base is also used.

Wax polishing with proprietary polish is also popularly used. This polish may be made at site by mixing a 25% solution of melted beeswax in turpentine together with pigment at the rate of 60% by weight of beeswax. The wax is applied on the floor which hardens after 12 hours and the surface is sprinkled with French chalk and polished with dry cloth. About 200 gm of beeswax shall cover an area of 10 m².

If the floor has to be roughened, it is usually done by washing the floor with dilute hydrochloric acid. The dilute acid is applied at the rate of 0.3 l/m² of floor area. The acid is left for 15 minutes and then brushed. Then the floor is thoroughly cleaned with water. If need be three successive applications may be given.

 

Other Floors

All stone floors may be maintained by mopping with mild detergent and water at regular intervals.

Ceramic tile floors are easy to maintain. Soap and water can be used to clean the floors and special care has to be taken to clean the joints. Stains, if any, may be removed as explained in marble floors.

Wooden floor is to be cleaned and kept bright by polishing with beeswax or ready-made wax polish.

 

MAINTENANCE OF DOORS AND WINDOWS

In the maintenance of doors and windows both wood work and glass, work should be taken care of.

 

Maintenance of Woodwork

Woods in general get deteriorated with time due to water and direct exposure to sun. However, teak wood may need less maintenance. Other woods should be periodically painted and kept clean. In moist conditions, both dry and wet rots grow which will be the worst in the toilet room. This can be prevented by providing adequate ventilation and painting.

 

The bottom of bathroom doors has to be protected by painting with waterproof paints. White putty glazing is used for ordinary wood and in teakwood glazing with beads is usually carried out.

 

Maintenance of Glass

Glasses fitted to doors and windows are kept clean using clean tepid water. In order to remove dirt and stains cleaning liquids available in the market may be used. Instead, cleaning can be made by mixing two tablespoons of household ammonia or white vinegar with

1.25 l of water. This is sprayed using a sprayer. Cleaning has to be taken up from top to bottom and the glass is dried by a cotton swab followed by a crumbled newspaper. One side has to be wiped horizontally and the other side vertically.

 

MAINTENANCE OF WATER SUPPLY SYSTEM

Sumps and overhead tanks are to be in closed conditions and should be cleaned periodically. Exposure of sump and overhead tanks lead to mosquito breeding and the formation of algae.

Taps and other fixtures should be kept in working condition so as to avoid wastage of water. They should be repaired wherever they become defective. Taps, chrome fittings, basins, etc., can be cleaned with liquid ammonia in water. Material for polishing of metals is also available in the market.

 

MAINTENANCE OF SANITARY APPLIANCES

The main problems with sanitary applications like water closets, washbasins, etc., are the growth of fungus and algae. A solution of chloride of lime (bleaching powder) in hot water will remove surface stains from ceramic ware and tiles. A simple application of moistened cloth in hot water and a little paraffin will effectively restore the lustre of porcelain and glazed surfaces. There are ready-made cleaning materials which are also available in the market. If the sewage is to be treated by a septic tank, chemicals and detergents should not be used as they may kill the bacteria in the septic tank.

 

MAINTENANCE OF DRAINAGE SYSTEM

All the soil and waste-disposal system must be kept clean and should be in working condition. Otherwise, nuisance and unhealthy conditions prevail. Main items of the drainage system to be taken care of are discussed below (Varghese, 2012).

Fittings Inside the Buildings

Water taps, wastewater pipes, traps in fittings, grating above floor trap, etc., should be periodically checked. This is done by pouring water on them and examining their performance. Otherwise, they are liable to be clogged if the passage of water is not with adequate force. Gratings at bathrooms have to be periodically checked for clogging due to hair, oil, etc. Blocking if any may be removed using drain cleaning compounds or manually wherever feasible.

 

Waste and Soil Pipes

Waste pipes and soil pipes which are fixed on the walls are to be checked periodically. Wherever feasible PVC pipes may be used with balloons on the top should be checked and replaced if necessary.

 

Gulley and Manholes

Before the onset of monsoon, gulleys, manholes, manhole covers and drain pipes are to be examined. In order to prevent backflow from the street sewer, the outlet to the sewer should be checked. By chemical sprays, cockroaches are to be destroyed and stagnation of water should be avoided.

 

Roof Drainage System

Before the rainy season, the roof drainage system should be inspected. Horizontal and vertical drainage systems are to be cleaned and leakages repaired. Rectification should be attended to, particularly horizontal drain pipes, to prevent the blockage of wastewater.

 

Septic Tanks

Grease, slow decomposing matter, etc., should be avoided in the drains for the efficient working of a septic tank. Further drain-cleaning chemicals should be avoided which can kill the bacteria in the septic tank.

When the depth of the sludge and scum exceeds half the depth of the tank, digested sludge should be removed. A portion of the sludge should be left in the tank to act as a seed to the fresh sewage. If the action in the septic tank is dull ¼ kg of brewer’s yeast is added to the tank to hasten the action. Signs of a defective system is to be noticed when foul colours appear from the drains or the tank and growth of lush vegetation over the tank. If water backs up in the drain, it is to be realised that clogging by sludge and scum has happened.

 

MAINTENANCE OF PAINTWORK

Washable paints can be cleaned with clean water. Most of the paints, viz., soda, soft soap and other alkaline substances are injurious. In order to remove stains, they should be highly diluted and removed off the paint with clean water as soon as the dirt is removed.

Re-paint of surfaces have to be done before the old paint disintegrates. Quality of paint contributes to the life of the work. Frequent painting of external surfaces may be prevented by the use of special exterior paints. Also, special paints may be used to paint the underside of the wet area, such as bathrooms and lavatories if wall tiles are not provided.

All steelworks are to be carefully observed. They should be regularly cleaned with clean water. Rusted parts, if any, should be removed and re-painted. Special attention are required if steel windows are used in buildings.

 

MAINTENANCE OF BRICKWORK

Cracks are frequently found in brick masonry walls. Causes for such cracks have been discussed in the previous post. It has been discussed that prevention of cracks in brick masonry may be avoided by proper foundation design and providing different joints such as expansion joints, isolation joints, sliding joints, etc.

Maintenance of brickwork involves in cleaning, removal of efflorescence, repairing of cracks, re-painting brickwork and re-painting old brick joints.

 

Cleaning Brickwork

Brickwork has to be cleaned with steam or steam and hot water jets. This treatment is suitable for fine-textured and hard-burnt bricks. Sandblasting can also be done. However, this disturbs the texture of the bricks and absorbs the painting.

 

Removal of Efflorescence in Brickwork

Soluble salts after drying get deposited on the surface of the walls as a white layer. These salts may be present in the material of the walls and come out. Sources of these salts are mortars and plasters. As moisture is the cause for the creation of efflorescence, this can be checked by proper damp prevention.

Efflorescence can be removed by scrubbing those portions on the wall with water and a tough brush. For effective use instead of water, 10% of the solution of muriatic acid may be used. After this treatment, the wall has to be rinsed with clean water or with a weak ammonia solution.

 

Repairing of Cracks in Brickwork

Cracks in brickwork are rectified by adopting the following procedure:

1. If the cracks are less than 1.5 mm in width, the cracks may be filled with commercially available putty.

2. Wider cracks are repaired by releasing them out to about 25 mm and re-filling with 1 cement, 2 lime, 9 sand mortar or any crack-filling material available in the market.

3. Still wider cracks may have to be stitched by using reinforced mortar or concrete stitching blocks.

 

Re-pointing Old Brickwork

In the case of brickwork which is pointed may be needed to re-point in order to improve the appearance and to make it watertight. Generally, mortar at the pointed portions gets lost due to rain, wind, freezing, etc. The following procedure may be followed for re-pointing:

1. The joint of the old mortar is loosened and scraped out and cleaned for a depth of at least 3 mm and wetted with water.

2. New mortar is applied to the joints with a special trowel and pointed as per practice.

 

Re-painting Brickwork

Re-painting is necessary for walls that have been previously painted. The type of paint and colour should be decided and accordingly, the surface has to be prepared.

 

MAINTENANCE OF STONEWORK

Maintenance of stonework involves in removing efflorescence and stains, repair of cracks and waterproofing.

 

Removal of Efflorescence in Stonework

The appearance of efflorescence occurs commonly due to use of the certain type of mortars. Removal of efflorescence has to be done as done in brickwork. Stones are to be kept saturated with water to remove the action of acids.

 

Removal of Stains in Stonework

Removal of stains can be done easily if its origin is known. Iron stains show a rusty appearance which can be removed by rinsing the area with a solution of ½ kg oxalic acid in 5 l of water. After 2–3 hours, the surface should then be scrubbed with a brush and clean water. Darker stains may be removed with six parts of water, one part of sodium citrate and one part of glycerine, made into a paste with adequate whiting. This paste is applied on the surface and then kept for a few days.

For very deep and dark stains, one part of sodium citrate is mixed with six parts of water. This solution is applied to the surface of stains. This is followed by covering the surface with a thin layer of sodium hydro-sulphite crystals and removed after an hour. This may be repeated if needed.

 

Repair of Cracks in Stonework

Repairing of cracks has to be attended to by ensuring that the settlement causing the crack has ceased. This generally takes about one year for the complete settlement.

Small cracks are cleaned with a wire brush and a thick paste of cement mix is forced into the crack. In order to get a firm key for the mortar, large cracks should be raked. An inverted V groove is made with a minimum of 1 cm depth. A cement mortar of 1:2 ratio is applied with less water. The mixture is forced into the crack to get a firm bond. Along with this mixture expansive agents are added to improve the bond.

 

Waterproofing of Stonework

In order to keep the stone masonry free from dampness, efflorescence, frost action, etc., colour-less waterproofing materials is applied waterproofing materials obtained from heavy petroleum distillates, oils or insoluble soaps are best. It is difficult to waterproof very closely textured stones. Waterproofing materials substances containing resins are not suitable for fine-textured stonework. Waterproofing causes some dislocation which goes from the stones in course of time.

 

CRACKS AND REMEDIAL MEASURES IN CONCRETE

Causes of cracks, remedial measures and repair of cracks in concrete are discussed.

 

Causes of Cracks in Concrete

Cracks in concrete may be plastic shrinkage cracks, settlement cracks, cracks due to bleeding, cracks due to delayed concrete casting and cracks due to construction effects are discussed the previous post.

 

Preventive Measures for Crack in Concrete

Preventive measures for cracks in concrete are discussed in Section 8.11. Apart from them, joints in concrete structures are provided to continue a specific work or prevent cracks due to change in temperature.

The following two types of joints are usually provided in concrete structures:

(i) Construction joints

(ii) Expansion and contraction joints

 

1. Construction Joints

This type of joints is provided at the location where the construction is stopped at the end of the day’s work or for any other reason so as to bridge the old work and the new work by a proper bond. Such a situation generally occurs when large concrete work has to be executed which cannot be done within a day.

If the work is well planned such that the day’s work is to be stopped at an expansion or contraction joint, in such a case there is no need for a construction joints.

The construction joints may be vertical, horizontal or inclined depending on the type of structure. In the case of inclined or curved members, the joint should be perpendicular to the axis of the structural member. The position of the construction should be well planned and constructed keeping in view the stability of the structure. Construction joints may be provided for structures that are vertical, horizontal or inclined (Fig. below).

Construction joint in different positions

 

Depending on the type of concrete structures the following factors should be considered.

(i) Columns

Columns should be concreted to a few centimetres below its junction with the lowest soffit of the beam. Construction above joint should be at least 4 hours after the completion of the joint. Care should be taken such that the construction joint is at the location of least bending moment.

(ii) T or L Beams

The ribs of T or L beams are first concreted and then slabs forming the flanges are concreted up to the centre of the rib (Fig. below). In certain situations, if a construction joint has to be provided between the slab and beam, the rib of the beam is concreted up to 25 mm below the level of the soffit of the slab and the joint should be located at that level.

Construction joint on T-beam

 

(iii) Simply Supported Slabs

In slabs supported on two sides, the construction joint should be vertical and parallel to the main reinforcement. Alternatively the joint may be provided at the middle of the span perpendicular to the main reinforcement. For two-way slabs, the construction joint is provided near the middle of either span.

 

(iv) RCC Wall

In this case, the location of the joint depends on the convenience in placing the framework and the access of compaction of concrete. The continuity of the joint is made by the formation of a key (Fig. below (a)). The arrangement of the formation of key and the finished position of the key is shown in Fig. below (b).

 

Construction joint in RCC Walls

 

2. Expansion and Contraction Joints

These joints are provided in all concrete structures when the length exceeds 12 m. These joints are made to satisfy the following requirements:

(i) To accommodate for changes in the volume of concrete due to temperature.

(ii) To retain the appearance by maintaining the same shape of the concrete structures.

The joints are filled with some elastic materials like filters or dowels of keys. The quality of the filter should be in a position to withstand cold weather. It should be compressible, cellular and not brittle. The Conventional materials used as filters are strips of metal, bitumen-treated felt, cane fibre-board, cork, softwood, etc.

The provision of dowels or keys is to transfer the load. The movement due to shrinkage is controlled by the contraction joint. The contraction joint may be complete or partial. In the complete contraction joint, there is complete discontinuity of both concrete and steel (Fig. below). In the partial contraction joint, there is a discontinuity of concrete but the reinforcement bars are continued across the joint (Fig. below).

 

Complete contraction joint

 

Partial contraction joint

 

Stitching of Cracks in Concrete Members

At times cracks do develop in concrete members due to several reasons such as the design of construction deficiency, problems with concrete, disturbance at an early stage, etc. If such cracks are localized in nature they can be repaired either by epoxy grouting or by stitching. The choice of either of them depends on the discretion of the concerned engineer and the intensity of the cracking (Gambhir, 2010).

Stitching consists of drilling holes on both sides of the crack, and inserting U-shape metallic strips (stitching dogs) spanning across the cracks. The bonding of the metallic strips with parent concrete can either by with non-shrink grout or an epoxy-based bonding system. It is preferable if the metallic strips are variable in length and orientation with closer spacing at the ends of cracks (Fig. below).

Stitching of concrete cracks

 

However, the stitching does not close a crack, but only prevents it from further widening. Such stitches, when encased with an overlay have been reported to be performing well in several cases.

 

Repair of Concrete by Gunite and Shotcrete

Gunite is one of the popular methods undertaken to repair cracks and other damages in concrete members. Guniting is the process of injecting mortar with a low water-cement ratio at high pressure through a nozzle. This method has been improvised in that only concrete with small-sized coarse aggregate instead of mortar is used. This method is called shotcrete.

In both methods, the affected concrete part should be cleaned before the operation and gunite or shotcrete is applied. Former small thickness or width of gap gunite is used whereas shotcrete is recommended for larger thickness. The materials used for gunite are cement, sand and water and for shotcrete are cement, sand and small aggregate and water. For the quick setting of gunite, accelerators are also added.

 

CHECKING BUILDING LEAKAGE

Although adequate care has been taken by providing weatherproofing of roofs, leakage may occur with time due to a lack of proper maintenance. Leakage of the roof due to rainwater may spoil the materials stored in the room, may damage the electrical circuits, may wet the walls, etc. Leakages may occur in different types and different parts of a roof which are discussed below.

Leakage in Sloping Roofs

All parts of the sloping roof are to be checked for leakage. It is difficult to repair after construction, particularly tiled roofs. It is generally recommended to apply a waterproofing coating at the construction stage itself. Tiled roofs leak during heavy rain due to lack of this precaution.

Other sloping roofs like folded plates, shells, etc., are made out of concrete. These roofs would not have been compacted properly due to the sloping surface. During normal rains, there is no problem with leakage. During heavy rains, water may seep through the concrete and tend to leak. A cement coating may fill the porous concrete followed by a waterproofing coating that may stop further leakage.

 

Leakage of Flat Roofs

Following preventive measures and repairs may be undertaken to prevent leakage.

1. During the construction stage itself, flat concrete roofs are to be cured perfectly. Any leakage noticed at this stage can be rectified easily. All surfaces can be given a coat of hot blown asphalt after curing.

2. Adequate slope may be given to the drainpipe joints such that stagnation of water is prevented.

3. Wherever the horizontal surfaces meet the vertical or inclined faces, fillets are to be provided. The gap formed with time has to be closed periodically.

4. All the entry points of the rainwater should be checked and should not be blocked by leaves, wastes, etc.

5. Weathering courses, like flat tiles, laid on the roof should not crack. If cracks are found they should be closed immediate by grouting or otherwise.

6. Very porous concrete slabs may have to be grouted.

 

Leakage Through Junction of Walls and Sunshades

This is very commonplace where the leakage occurs which are to be checked and rectified as discussed below.

1. At the construction stage itself, proper slope and drainage arrangements are to be checked. Any architectural features made over sunshade should not give room for the stagnation of water. A throating at the bottom end of sunshades shall make the water drip properly.

2. In long sunshades there is a possibility of cracking at the ends. Such cracks make room to flow water on the walls. These cracks should be filled with bituminous or elastomeric compounds. The top of the sunshade should be kept clean always, particularly before the onset of the monsoon.

 

Leakage Through Wall Cracks

All the external cracks found on walls should be deepened to 5 mm and filled with paintable sealant. In order to keep the external walls crack-free, waterproof cement or external paint may be used. Walls containing air-conditioning or other electrical connections may be painted with silicon paint to prevent the wetting of walls during rains.

 

 

MAINTENANCE OF ELECTRICAL SYSTEM

It is better to have an ELCB trip switch in the electrical system of the buildings. This is helpful to show the earth leakage. All electrical switches should be kept clean, particularly ones at the kitchen which are liable to be clogged up by grits accumulated. In order to avoid the menace of ants and white ants, it is better to keep anti-ant chemicals in the switch boxes. If the performance of bearings, condensers, regulators, etc., is not good, they have to be attended to. High amperage gadgets like heaters, air-conditioners, etc., are liable to get heated up and burnt. They should be plugged tightly or should be connected through fused outlets. It is advisable to have phase-changing devices in the electric supply system and thereby changing phases wherever there is a need. Savings in electricity can be made by the use of fluorescent lamps, LCD lamps for lighting and capacitance type fans.

 

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SOURCE: Basic Civil Engineering

Fourth Edition

MS. Palanichamy

Vice-Chairman

Tamil Nadu State Council for Technical Education Chennai, Tamil Nadu