Mapeguard Board is a multipurpose, premium-performance, lightweight, rigid, waterproof backer-board panel made with a high-density, extruded polystyrene core; Features a high-strength, waterproof membrane and facer on both sides to provide water and vapor protection; Suitable for use under ceramic tile and stone installations for both residential and commercial interior applications; Uniquely engineered, multi-layered design available in thicknesses from 1/4" to 2" (6 mm to 5 cm); Can be used on walls, floors, ceilings, countertops, and for fabricating room partitions, benches, seats, and furnishing elements.