Cavity Drain Installation

There are four different grades of basement dryness (as referred to in BS 8102). Grade 4 is a totally dry environment suitable for the storage of archives and antiques. Grade 3 and 2 is for office and domestic use and Grade One is suitable for plant rooms where minor leaks are tolerable. Water damage to subterranean structures is a highly contentious issue with many views about what is the best way to treat the problem. With many years of accumulated expertise, Cemplas understands that the optimum remedy will depend on a host of factors such as the: age of the building (existing buildings only) proximity to water courses level of waterborne contaminants condition of the existing masonry or brickwork nature of the water ingress. A Cemplas diagnostic survey will identify the prevalent factors. The remedy will also depend on the intended use of the basement, and a cavity drainage system using a studded membrane and a pump to drain the water may be preferable to using a cementitious tanking approach.


Cavity drain membranes work on the principal of allowing water to continue to penetrate the structure but control it in the air gap and divert it to a suitable drainage point or pump (if required). Cavity membranes do not allow pressure to build up against the internal construction, and the air gap behind the membrane allows the structure to ‘breathe' and dry out. The membranes are impermeable to water, and gas and water vapour, thus protecting the basement internal space from dampness. Membranes are loose laid on floors and fixed to walls using special plugs and sealing materials. Cavity membranes can be fitted with little or no preparation to the substrate. Once fitted, wall surfaces can be dry lined or plastered directly, and floors can be screeded, or a suitable dry board system installed. This method of basement waterproofing allows decoration and floor finishes to be completed almost immediately, without long drying out periods.

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