CE’s Circular No.193 Sub : Water Proofing of Building & Structures LEAKAGE & DAMPNESS IN BUILDINGS Leakage in building, specially roofs has been a cause of concern on the Indian Railway. There is hardly any railway building, which does not show signs of leakage. Apart from inadequate water-proofing, which has been dealt with in detail in these papers, our failure to observe certain precautions at the time of construction of these buildings largely results in leaky roofs. 2. PRECAUTIONS DURING CONSTRUCTION OF BUILDING Some of the essential precautions to be taken at the time of construction are as follows:- i) Every building plan, whether for new building OR for addition/alteration to new building, must give details of terracing to be provided , water proofing system for roof with details of joint with parapet wall, sunken `floor and down water pipes in scale not smaller than 1:20. ii) Specifications laid down by the manufacturers of the water proofing products should be followed scrupulously to ensure that no air bubbles are left between the under lying surface and the water proofing layer. Adequate overlaps should be provided for the water proofing layers, including cover upto the parapet wall. A few sketches are enclosed as Annexure –I (5 sheets) indicating the method of laying water proofing layer at the junction between roof and the parapet wall. There are a large number of relevant Indian Standards and Code of practice available. Some of these are listed at Annexure-VI. Their provisions regarding material & execution may be followed. iii) Drainage slope of the roof is one of the most important factor. For the guidance of the field Staff, each building plan must also incorporate a roof plan, showing the position of drainage Pipes and direction and extent of slope on the roof. Drainage slope should not be flatter than 1 in 80 and should preferably be 1 in 40. There should be no undulations in the roof surface, which may result in accumulation of rain water. At the time of construction, the roof levels should be personally recorded by the Inspector of Works and 100% check exercised by the Assistant Engineer. Extra care is necessary for construction of golas, coping and joints. iv) At the extension joints in buildings, water proofing has to be strengthened by inserting a PVC Or a copper plate to prevent water from seeping. Some of the arrangements required for the Same are enclosed in the sketch placed as Annexure-II. (5 sheets). These joints should also be plugged by a good sealant. Polysulphide based flexible sealants have good adhesion to concrete surfaces and can be compressed or stretched upto 50% of the width of the joints and are good material for sealing of expansion joints. Depth of the expansion joints above the copper/PVC plate should normally be kept half of the joint width and should not exceed 20 mm.
Water Proofing of Building & Structures
May 01, 2023
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