Do not believe the FRP suppliers when they advertise FRP panels as waterproof. These panels need wooden backer boards that absorb moisture, leading to dampness and rotting. This further paves the way for mold and mildew formation that contaminates the interiors. Instead, choose PVC panels that are inherently moisture-resistant, anti-mold, and extremely durable. These panels have a non-porous surface that does not absorb moisture, preventing dampness and mold formation. Visit the Duramax website for more details.