Question
What is a Cavity Drain Membrane?
Expert Answer
A Cavity Drain Membrane is a High-Density Polyethylene (HDPE) sheet with a studded profile. It is mechanically fixed to basement walls. The studs create an air gap (cavity) between the wall and the membrane. Any water penetrating the wall runs down this gap into a drainage channel, keeping the internal finish dry. It is a key component of Type C waterproofing and is ideal for damp or salt-contaminated substrates where tanking might fail.
