One critical area of waterproofing is to ensure the detail you use to seal the penetrations for the shower mixers/taps and their associated outlets not only completely seals the penetrations from water ingress from the outside, but will also provide protection to the wall cavity.

Where a BGT system connects with a Damp Proof Membrane (DPM) is a detail that many designers have drawn without fully understanding how these dissimilar membranes are connected.

The Waterproofing Membrane Association Inc. (WMAI) develop a range of Codes of Practice (COP) for Water Proofing Membrane(s) (WPM) for all situations.