The Cavity Drainage Membrane (CDM) system provides an exceptionally fast and convenient method of waterproofing walls, floors, and ceilings on new build and refurbishment
projects. It is especially useful for waterproofing basements and underground structures, however, it can also be used to waterproof walls and floors above ground level.
The design of the system is such that an air gap is created between the highly water resistant membrane and the substrate. This gap enables the substrate to 'breathe' and equalises water vapour pressure. The membrane is attached to walls and ceilings by means of simple to fit, sealed fixing plugs. While on floors there is normally no need for any form of fixing.
CDM can be covered with a batten and plasterboard finish or a dry wall lining. A special version of the membrane, which has a glass fibre mesh on one side, can also be plastered. On floors it can be screeded over or overlaid with a floating timber floor.
If it is possible that free water will enter the cavity behind the membrane then a drainage facility, possibly incorporating a sump and a pump, will need to be built in.
CDM systems have a life expectancy of 50 years.