High Quality Content by WIKIPEDIA articles! A rainscreen drainage plane is a separation between the veneer and the weather resistant barrier of a rainscreen. It provides predictable, unobstructed path drainage for liquid moisture to drain from a high point of the wall (where it enters) to a low point of the wall (where it exits) the wall detail. The drainage plane must move the water out of the wall system quickly to prevent absorption and consequential rot, mold, and structural degradation.