Waterproofing Membranes. A water-proof membrane is a thin layer of water tight material that is laid over the surface. Stagnated water is likely to seep into the structural slab overtime. In flat roofed terrace, the membrane is laid over a filler material that is sloped to ensure that water is drained away by drainage pipes. The membrane is then placed over this layer of filler material. Tiles can be added over the membrane. This will ensure that water does not seep into the roof slab.
Membranes are made of thin layers of water-proof materials usually 2-4 mm thick. Membranes can be of two types: sheet based or liquid based.
Sheet Based Membranes
Sheet based membranes come in the form of rolls. These are unrolled and laid on the firm surface. One of the most common sheet based membrane is the bituminous waterproofing membrane. This membrane is stuck to the roof surface by melting a tar based adhesive on the membrane using blowtorches.
These membranes can be measured and cut to the surface area requirements of the roof. Adjacent membranes should overlap using the same tar based adhesive. The overlapping width can be around 100 mm. This will prevent vulnerable joints and water from seeping in through the gaps between the membranes.
Liquid Applied Waterproofing Membranes
These are the kind of membranes that come in the form of liquid that can be sprayed or brushed onto the surface. By spraying, the liquid forms a monolithic membrane, with no laps, welds or seams. Unlike sheet based membranes, the thickness of liquid applied waterproofing membranes are not predetermined. Hence, the thickness can be controlled as per requirements, by varying the amount of liquid applied per unit area. However, care must be taken to provide the right thickness as a layer that is too thin can easily break.
The application process is quick and can be finished within a day. However, for large areas that are to be done on successive days, cold joints can be introduced by overlapping new membrane to the old. Liquid applied waterproofing membranes usually have the ability to stick to itself. Hence, cold joints can be entertained.
The key advantage of liquid applied waterproofing membrane over sheet based membrane is the absence of joints, which usually tends to compromise the waterproofing.