As the name suggests, a rainscreen system is any kind of siding that is meant to provide a non-fully sealed outermost layer. A rainscreen can be brick, fiber cement panels, wood, metal, or any other kind of siding system that you can imagine. The key to a rainscreen system is creating a pressure-equalized drainage plane behind the outermost layer exposed to the weather. This is typically achieved by installing the siding with a “gap” behind it, and allowing the joints to remain open in between panels or planks.

The main benefit of the rainscreen system is that unlike conventional sealed systems. Water that gets trapped in the wall is allowed to drain down the waterproofing layer and back outside of the wall. In a truly sealed system, there is often a negative pressure buildup inside the wall cavity, sometimes created by wind against the external face of the building, or air conditioning / fans /etc. from the inside of the building. This becomes a problem in some cases where the the space behind the siding that can essentially “siphon” the water from the outside of the building back into the building, and prevent appropriate drainage.

With a truly pressure-equalized system, as in a rainscreen, the pressure on the exterior of the wall is the same as the pressure on the inside of the wall, allowing a true gravity drainage system inside the wall cavity. Thus, the cladding essentially functions as a “wear layer” and primary surface for shedding water, even if it is not fully sealed. Any water that makes its way behind the outermost layer is allowed to drain out, creating a semi-permeable and “breathable” wall system. This breathability prevents dampness and mold from building up in the wall.