The best water-proofing for any surface is a proper slope. Having said that we have to accept the fact that the slope alone is not going to withstand the rigours of nature for 10 years and beyond. The solution is to provide protective layers or actually two (double) protective layers.
Experts in Building Waterproofing Services ensure that the first layer is exactly on top of the flat terrace slab, with a gentle slope of 1:500. There are three important criteria for this layer:
- Presence of weep holes that shall indicate dampening of the surface due to an ageing of the top water-proofing layer, before it affects habitable spaces.
- A homogeneous layer anchored at a right angle joint of the terrace slab and parapet wall.
- An elasticity of the admixture present in the base layer.
The base layer shall have Coba with brick or ACC block bats laid to a slope of 1:90/1:100, depending upon the extent of rainfall and distance of ridgeline to run-off spot for rainwater. The concrete mix recommended is 1:3:6 or max 1:2:4, while in certain cases, 1:4:8 may be acceptable but not lower. Admixtures of polymer in this layer shall help in reducing the setting time thereby giving time for the skilled masons to gradually work on the slopes. (In olden days ‘GUR’ was the admixture used).
The second waterproofing layer, laid above the Coba layer to a thickness of max 1.5mm in 2/3 coats with reinforcement shall render the surface water-proof for a minimum period of 10 years. Please note that the 1st and 2nd layer should be carried up to 300mm above the flat slab onto the parapet wall unless otherwise specified.
The top surface visible to the eye can be
- China Mosaic
- Stone floor
- Special ceramic tiles not more than 200mm in size.
Waterproofing in heavy rains should be avoided if possible and proper care should be taken to break the joints, as lesser the length of joint, the better the result.