Liquid rubber waterproofing for a flat roof

Liquid rubber waterproofing can be used to waterproof a flat roof when the liquid-applied waterproofing is applied in at least three coats. For flat-roof waterproofing, the finished surface must be seamless, permanently elastic and resistant to standing water. Rainwater does not run off a flat roof as freely as it does from a pitched roof, so it collects in low points and around junctions, where leaks tend to develop first.

The substrate must be clean, dry and sound; suitable substrates include concrete, bitumen, metal and plastic. Liquid-applied waterproofing can be brushed or rolled on, while larger areas can be treated by airless spray application. Once dry, it forms a seamless rubber membrane that bridges cracks, accommodates movement in the substrate and remains watertight under standing water.

Roof outlets, rooflight domes, roof edge terminations, and pipe and cable penetrations are subject to particularly high stress and require close attention. At these points, the waterproofing is reinforced with an embedded fabric layer. Where only isolated areas of an existing flat roof are damaged, local treatment with liquid-applied waterproofing is often sufficient, without a complete renewal of the roof membrane.