UNIT 11 WATER AND DAMP PROOFING Structure 11.1 Introduction Objdvea 11.2 Principles of Water Proofing 11.3 Procedure for Damp Proofing~WaterProofing 11.4 Dampness and Leakage 1 1.4.1 Signs of Dampness 11.4.2 Detection of Dampaess 11.5 Causes of Dampness 11.5.1 Condensation 1 1.5.2 Rain Penchation 1 1.5.3 Built-in Water 1 1.5.4 Pipe Leakage 11.5.5 Spillage 11.5.6 Seepage I 1.5.7 Rising Dampness 11.5.8 Hygroscopic Salts 11.6 Prevention of Dampness 11.6.1 Planning and WinStage 1 1.6.2 Constmction Stage 1 1.6.3 Remedial Meatjures and Treatment 11.7 Dampness in Old Structure and Remedial Measures 11.8 Water Proofing 1 1.8.1 Integral Water Proofing 1 1.8.2 Surface Treatments 1 1.8.3 Metallic Water Proofing 11.9 Different Methods of Waterproofing and Case Studies 1 1.9.1 Water Proofing Basements 1 1.9.2 Polyma Plaster for Roof and Hm- PROOFSOL 1 1.9.3 Wat,er Proofing of Roofs -Nina Industries Method 11.9.4 \V&r Proofing by Algiproothg Method 1 1.9.5 Case Studies 11.10 Spectrum of New Water Proofmg MaterialslSystems 11.11 Summary 11.12 Answers to SAQs 11.1 INTRODUCTION You have already learnt about strengthening of stone and brick masonry and about repair of floors, in previous blocks. Now in this unit, dampness and water leakage in buildings their causeslreasons and ways and methods to avoidlprevent them is dealt with. Dampness and water leakages in buildings is a serious concern of Civil Engineers all over the world. In spite of proper supervision during construction, buildings are still affected by these problems. Building materials such as bricks, concrete, plaster, timber etc., have a moisture content which under normal circumstances is no cause for concern. ?be rise in moisture content of these materials to a level where it becomes visible or when it causes deterioration is the real dampness. Objectives At the end of this unit, you should be able to: know methods to detect dampness, find the causes for dampness, know the methods adopted to prevent dampness, and Repair & Preventive understand the various types of water proofing methods. Maintenance Techniques Thus you will be able to guide the artisans to take care during construction to avoid dampnegs and provide correct water proofing. Definition I Dampness is defiid as presence of moisture in air or on surface or diffused I tbrough solid. Any indication of slight wetness or moisture is termed as dampness. 112 PRINCIPLES OF WATER PROOFING Most of be building materials used in construction are exposed to water and are not impervious and do allow water to enter into their systems. Sometimes the building materiais may be good but the bondihi materials like mortar may be pervious and may permit water inside. Cracks occur due to expansion and shrinkage of construction material which in turn form voids which allow water to pass through. Some materials absorb water from outside. Thus the: basic principle involved to prevent dampness and avoid water proofing problems is to make construction materials voidsfree and avoid voids formation after the construction. If porous materials are unavoidable they have to be made impervious with materials in the pore filling class or covered completed with impervious layers to repel water. The pore filling materials fill in the voids, expand because of chemical reactions and thus enSure water dghtness. 113 PROCEDURE FOR DAMP PROOFINGIWATER PROOFING a) The source of dampness involk,d is to be established. b) If any hydrostatic pressure is involved including uplift pressure, measures to counter this pressure are to be adopted. c) The most common construction material, concrete must be fully compacted while casting. d) Decide whether water proofing is to be on the positive sidelface, i.e water face or on the opposite si& depending upon the construction details. e) Decide about the water proofing system-pore filling or repelliint. f) Follow instructions by the manufacturer in respect of specific materialslfiystemsused. 11.4 DAMPNESS AND LEAKAGE 11.4.1 Signs of Dampness In case of dampness it is very important to maintain a complete record from the period when it is first noticed. If it can be established that the occurrence of dampness is related to temperature or weather, this can help significantly in limiting the possible causes of the trouble. Signs of dampness which are directly evident are a) Stains on different surfaces of buildings. b) Visible water such as a fhofmoisture or drops of water on a surface. Bad smell, mould, insects, salts and other corrosion products also testify to the presence of dampness. Detachment and falling of paint films, wall papers, plaster, timber, ceiling plaster are indicative signs of dampness. Displacement of parapets, wall tiles, floor tiles and cracking of glass dwalls, also take place due to dampness. 11.4.2 Detection of Dampness There is no limit to the size of a dampness stain. One of the ways of telling whether a dampness stain is still active is to remove any growth of mould or efflorescence after a record hds been ma& of the condition and to see how much it returns before the next inspection. This way it can somet-s be determined whether the dampness is decreasing or increasing. Similarly it can be useful to draw a pencil line around the outline of the Water & ~~mp~~ooting dampness stain and to date it. The size of the stain depends on the material behind the surface. The shape of stain is not only informative but can also be conclusive. 'rhe crescent shape in the comer of a surface is conclusive evidence of condensation while the convex shape of a stain indicates that the source of water is other than cbndensation. 11.5 CAUSES OF DAMPNESS Dampness in buildings is generally due to bad design, faulty construction andor poor materials used. Structures built on high ground and well drained soil are far less liable to suffer from foundation dampness than those built on low-laying water logged areas where a sub soil of clay or peat is commonly found through which dampness will inevitably rise unless properly treated. A sub-soil through which water can easily pass such as fm gravel,m., sandy soil or a soil containing light clay, will usually keep the foundations fairly In coastal towns walls are particularly prone to seepage because of the high humidity and salt particles in the atmosphere. Since salt absorbs water, the walls become damp. When that happens, the plaster peels off, exposing the steel reinforcement. In course of time, the steel is corroded, further weakening the structure. The sand mixed with cement for the reinforced concrete is also sometimes salt-contaminated,endangering the life of the structure. Leaks generally occur from the sanitary fittings. In new constructions, leaks are due to inadequate curing of the concrete, substandard quality of the concrete etc. The various causes for dampness are explained below: 11.5.1 Condensation The deposition of moisture from the atmosphere, either internal or external, on relatively cold surfaces. Condensation takes place on surfaces at temperatures below the dew point. Internal air should be allowed to circulate by providing proper ventilation especially in closed rooms. 11.5.2 Rain Penetration Penetration of rain water in a structure takes place due to usage of defective materials, faulty designs, or construction techniques. AU constructional defects allowing penetration of rain water in any part of the structure should be immediately rectified. The building should be dried thereafter by natural ventilation, by keeping the windows open or by using suitable heaters. Dehumidifiers may be used keeping the windows closed. Fast drying methods which affect timber joints, plaster, paint and wall papers, etc., should be avoided. 11.5.3 Built-in Water The presence of water which has been enclosed with the structure during ,the construction I process, such as water used in mixing concrete, mortar, plaster, water from atmosphere like rain, snow, frost and dews. Large quantities of water used during construction evaporate into the internal air of a building and become available for condensation In I unoccupied new buildings, this effect is felt more. The problem may, however, disappear 1 completely within two years, excepting in the case of water entrapped within the roof of the structure. The remedy lies in drying out the affected areas of the building and providing good ventilation. ' 11.5.4 Pipe Leakage The leakage of water from water supply line or drains and trenches. Leakage from a water supply line or rainwater pipes or a drainage systems, if not attended to in time, proves to be an effective source of dampness. Such leakages should immediately be repaired and I water collecting near the fault point drained off. ' 11.5.5 Spillage I The spillage of water from industrial and domestic activities is an active source of dampness. similarly, waste waters are contributed by dwellings and industrial buildings I I Rep& & Preventive als?. To check spillage of water, remedial measures like the provision of proper drainagc Msintenaoce Techniques should be ensured. 11.5.6 1 Seepage The passage of wateran or in the ground through structure wholly or partly laid undergnbund. Seepage in buildings takes place due to passage of water wholly or partly below the ground water. Proper care during construction can make the structure ~eepage~fiee.External and internal drainage systems should be fitted with all possible care. 11.5.7 Rising Dampness The sloy rise of water from the ground up into the wallslfloors due to defective or missing damp-proofing coursesltreatments.