BS 8102:1990 considers that ‘drained protection’, in other words, a cavity drain membrane fitted to the structure, is the most effective and trouble free type of water resisting construction.Cavity drain membranes provide an alternative to conventional cementitious tanking systems, which work by holding water back.

They do not allow pressure to build up against the internal construction and the air gap behind the membrane allows the structure to ‘breathe’ and to some extent dry out.

The membranes are impermeable to water, gas and water vapour, thus protecting the basement internal space from dampness. The membranes are loose laid on floors and fixed to walls using special plugs and sealing materials.

The membranes can be fitted with little or no preparation to the substrate and once fitted, wall surfaces can be dry lined or plastered directly and floors can be screeded or a suitable dry board system installed.