Where the risk sits
On Class 1 buildings the highest-consequence areas are usually bathrooms, laundries, balconies above habitable space and terraces over garages. Failures are rarely a membrane defect alone — thresholds, falls and drainage are common contributors.
Sequencing on a house
Wet area membranes are installed after fixtures and penetrations are set and before tiling. External areas depend on screeds and falls being resolved first. Compressing this sequence is the most common cause of rework.