Waterproofing of Flat Terraces and Roofs:
How to waterproof a flat terrace
Waterproofing of flat terraces is a tricky problem in building construction, mainly because the surfaces are flat. This means that the water cannot run off the structure quickly, and will move slowly or pool above the surface, creating opportunities for leakage.
In addition, these flat surfaces require sumps or collection pits for the water to flow into before entering the vertical drainage pipes, which another great source of leaks.
It follows that rough terrace surfaces (such as crazy china paving) are not good for waterproofing, as they encourage slow movement or pooling of water. Smooth surfaces are better. The more slope you can give to the surface, the better. A slope of 1 in 100 or steeper is recommended for terraces.
In addition, these flat surfaces require sumps or collection pits for the water to flow into before entering the vertical drainage pipes, which another great source of leaks.
It follows that rough terrace surfaces (such as crazy china paving) are not good for waterproofing, as they encourage slow movement or pooling of water. Smooth surfaces are better. The more slope you can give to the surface, the better. A slope of 1 in 100 or steeper is recommended for terraces.
The best way to waterproof a flat terrace is to use a waterproofing membrane. This is a thin layer of waterproof material that is continuous, and offers no path for water to enter the structure.
The membrane is laid on top of the structural slab.
On top of the membrane, a filler material is laid. The filler material is necessary to give a slope to the finish of the terrace. This slope runs towards the drainage outlets.
The final layer is the finish. This may be a tile, or a stone, or any material that can withstand outdoor conditions. The finish and the filler layers themselves do not contribute to waterproofing.
The membrane is laid on top of the structural slab.
On top of the membrane, a filler material is laid. The filler material is necessary to give a slope to the finish of the terrace. This slope runs towards the drainage outlets.
The final layer is the finish. This may be a tile, or a stone, or any material that can withstand outdoor conditions. The finish and the filler layers themselves do not contribute to waterproofing.
Critical areas
The critical areas in membrane waterproofing - the areas where it is likely to fail - are the few areas where the membrane is not continuous. This occurs at the outlets, also called drainage sumps, where water collects before flowing into drainage pipes.
If a failure occurs, it cannot be easily rectified, as the membrane is not accessible. Therefore to correct a failure, construction workers will have to rip out the floor finish and the filler material, repair or replace the entire membrane, and re-lay the upper layers.
If a failure occurs, it cannot be easily rectified, as the membrane is not accessible. Therefore to correct a failure, construction workers will have to rip out the floor finish and the filler material, repair or replace the entire membrane, and re-lay the upper layers.
