Code of practice for general design details and preparatory work for damp-proofing and water-proofing of buildings
1988 Edition

According to IS 3067 Clause 6.2.1 for concrete and masonry roofs, preparatory treatments include cutting well-defined cracks into a 'V' shape and filling them flush with cement-sand slurry or IS 1580 bituminous caulking. Roof surfaces must be cleaned thoroughly to remove moss, fungi, and dust by wire brushing. For lime concrete applications, the surface should be roughened to ensure good adhesion. Masonry drain mouths need to be widened to 2.5 times the pipe diameter and rounded with cement mortar, while cast iron outlets require grooves cut around them to tuck in waterproofing layers. Around pipe penetrations, cement concrete angle fillets should be constructed with the waterproofing applied over them. Parapet walls taller than 450 mm require a groove 75 mm wide by 65 mm deep at 150 mm above roof level for waterproofing tuck-in, whereas shorter parapets have waterproofing carried over the top. A 75 mm radius cement mortar fillet should be provided at the junction of roof and parapet walls. The roof surface must be properly regraded and cured before waterproofing application.

IS 3067 advises scheduling damp-proofing during periods when the subsoil water level is at its lowest, typically the dry season. Designers need to collect critical information such as the highest water levels during rains, water table fluctuations, maximum water pressure, chemical composition of the subsoil water, and foundation details. Construction joints should be avoided or carefully treated, with proper support at expansion joints to withstand water pressure. A minimum working clearance of 600 mm around the basement is recommended for application. The mortar bed must be smooth and level, with 75 mm radius cement mortar fillets at horizontal-vertical intersections. The damp-proof course (DPC) should be 12 mm thick, composed of cement mortar (1:4) or cement concrete (1:2:4) incorporating waterproofing compounds as per IS 2645. DPC should extend vertically on the inner edges of brickwork, and floors should be finished up to the superstructure’s inner face. Dewatering arrangements include land drains with loose ballast and tar-felt covers, pumps, and bunds to prevent water backflow during treatment.

IS 3067 recommends cutting clearly defined cracks into a 'V' shape, cleaning, and filling them flush with cement-sand slurry or cold-applied bituminous caulking (IS:1580-1969). Roof surfaces, gutters, and drain mouths must be cleaned of moss, dust, and fungi by wire brushing. Around pipes penetrating roofs, a cement concrete angle fillet should be constructed with the waterproofing extended over it to prevent water ingress. Parapet walls exceeding 450 mm in height require a groove 75 mm wide by 65 mm deep at 150 mm above the roof surface for tucking waterproofing membranes; shorter parapets have waterproofing simply carried over the top. A 75 mm radius fillet must be provided at the roof-parapet junction. Drain outlets should be widened to 2.5 times the pipe diameter and rounded with cement mortar. Expansion joints need to be sealed with non-absorbent, compressible, watertight sealants to maintain waterproofing continuity.

IS 3067 endorses the use of bitumen felts and bituminous mastic (per IS 1346 and IS 4365), lime concrete (per IS 3036), and gunite (sprayed concrete) for waterproofing concrete and masonry roofs. Cracks should be treated by cutting and filling with cement-sand slurry or cold-applied bituminous caulking compounds (IS 1580). Surfaces must be cleaned and roughened where lime concrete is applied for effective bonding. Cement concrete angle fillets are recommended around pipes and at junctions. For parapet walls taller than 450 mm, grooves must be provided to tuck waterproofing layers, while shorter parapets have waterproofing carried over the top. Timber roofs are typically treated with bituminous felts and mastic following proper surface preparation, including caulking joints with bitumen-impregnated fiber, nailing boards to prevent curling, and sealing pipe penetrations with metal flanged collars.

IS 3067 requires maintaining continuous site drainage throughout damp-proofing operations. Dewatering methods such as pumps, well-point systems, or land drains should keep the subsoil water level below the working surface. In confined spaces, alternate pumping arrangements and shoring are necessary. For existing basements, damp-proofing is best performed in dry seasons after draining standing water, using well-point or floor pumps sealed with waterproof plugs post-treatment. Time scheduling should coordinate excavation completion, readiness of working surfaces, scaffolding, and pumping systems to avoid delays. Accurate site data on water table levels, pressure, and soil chemistry must inform design decisions. Dewatering ensures dry conditions, allowing effective and durable damp-proofing.