Cavity drainage systems or “type C” waterproofing usually utilise pre-formed high density drainage membranes, channels and sump chamber. These are designed so as to direct any water entering back out in a controlled and managed way. Typically cavity drain membranes are installed to the walls and floors these direct water into drainage channels. The channels then allow water to be directed to sumps or drains so that it can be removed safely from the building. Cavity drain membranes provide an alternative to conventional cementitious tanking system.