Traditionally, drainage planes consisted of tar paper installed shingle fashion behind exterior claddings coupled with a flashing at the base of each wall to direct rainwater that penetrated the cladding systems to the exterior. It was important that some form of air space or drainage space was also provided between the cladding system and the drainage plane to allow drainage.

Related Documents for Further Reading:

BSD-105: Understanding Drainage Planes

Info-301: Drainage Plane/Water Resistive Barrier

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