BU527 Drained and vented cavities (2010)

The cavity provides drainage and drying to manage any water that may penetrate the cladding in extreme circumstances. It is fundamental to the weathertight performance of the building that the wall assembly is designed and constructed to ensure that any water that may penetrate the exterior cladding can be managed by the drained and vented cavity.

This bulletin covers:

• drained and vented cavity construction including air pressure barriers, flexible wall underlay, rigid air barriers, flexible flashing tape, drainage and ventilation openings, cavity closure devices and cavity battens
• cavity maintenance, including ground clearance and cavity closure blockage.