What is Type C waterproofing?

Type C waterproofing is 'Drained Protection.' Instead of trying to hold back massive hydrostatic pressure physically, it accepts that some water may penetrate the shell but manages it. It uses a Cavity Drain Membrane (an egg-crate shaped plastic sheet) applied to walls and floors. Water runs behind the membrane into a perimeter drainage channel and is directed to a sump pump station, where it is pumped away. This is often considered the safest method for existing basements as it does not rely on perfect structural integrity.