water proofing of roof

1.1: Repair of rainwater leakage in the building

          The problem of rainwater leakage in the building can be classified as follows:-

1)Leakage in the flat roof  terrace 


                     Stagnation of water on a flat roof is one of the common reasons for leakage and dampness in the flat roof. Leakage happens in a flat roof due to bad drainage also.


                 The slope of roof terrace should be constructed in a way such that the rainwater drains off before seeping into the roof. The minimum recommended slope for a roof covered with tiles in 1 in 60. For a non-treats rough surface, it is 1 in 40.

  2)Leakage in shells and sloped roof


            Lack of compaction during the construction phase due to difficulty in compaction by vibrator. Use of porous concrete.


            Always use dense concrete. All the valleys should be checked for leakage and grouted at the construction stage itself. Waterproofing coating in the form of the bituminous coat can also be applied. Check for the provision of the gutter, cave gutter, valley gutter, and boundary wall gutter.

3)Leakage through Junction of wall and sunshades


            Stagnation of water at the junction between the wall and sunshade. Continuous long sunshades without joints or gaps tend to crack at the interval.


           Give proper slope for quick drainage of the sunshades at the construction stage. Provide a fillet or goal by plaster at the wall junction. In the case of a crack in sunshades, fill these cracks with an elastomeric compound that can accommodate the movement of joints. All leaves etc collected over the sunshade should be maintained, clean, especially during the rainy season.

4)Leakage Through cracks on external walls

        All the cracks that have been formed on the external wall should be deepened to 5 mm and filled with proper sealant.

5)Leakage at Junctions of outer walls with roof slab and other floor slabs


           Due to the difference in the expansion of concrete and masonry. If there is a small gap at the junction at the external face, the water that flows down the external wall tends to be sucked into the building.


           Provide a drip course with a projection with a shaped groove, called drip by extending the slab beyond the wall or by constructing a separate drip coarse in a framed building in the form of bend at the junction. In the case of the existing building, the joint has to be sealed with a waterproof sealant or by the application of elastomeric paint with glass fiber.

6)Leakage from external electric paints

          All the external electrical points and fitting should be sealed with good sealants and made waterproof. Any wires and pipes taken into the building should be bent down and then up to be drained properly. It should not carry water inside the building.

7)Leakage from expansion Joints of slabs or beams

Expansion or other joints provided by the designer in slab and beams should be properly filled with approved Joint Fillers. Joints fillers are special material that allows movement of the joints.

Leave a Comment

Your email address will not be published. Required fields are marked *