A rainscreen is an exterior wall arrangement that leaves a drainage and drying space behind the siding. Furring strips or a purpose-made drainage product hold the siding away from the wall’s water-resistive layer. Water that gets behind the siding can drain through this space, and a suitably ventilated arrangement also helps moisture dry out.
In home addition planning, ask whether a rainscreen is part of the proposed exterior wall assembly and how it will connect with the existing home. Review the siding, drainage space, water-resistive layer and flashing together. A rainscreen does not replace the rest of the wall’s moisture-control details. Its design should follow the chosen products’ requirements and provide a clear path for water to leave the assembly.