Architectural Detailing - Edward Allen, Patrick Rand
Often a wall cladding material and its joints are not waterproof. When this is the case it becomes necessary to collect and drain water out of the wall assembly. Cavity walls, or walls with an air space within them are designed to collect water that makes it beyond the exterior cladding. The cavity is a capillary break that forces remaining water to drop to the bottom of the cavity where it can be drained out of the building by waterproof flashing. This detail is common in brick walls.