Schluter's KERDI-BOARD building panels are a multifunctional tile substrate, which can also be used for creating bonded waterproofing assemblies with tile coverings. It consists of an extruded polystyrene foam panel, with a special reinforcement material on both sides and fleece webbing for effective anchoring in thin-set mortar.KERDI-BOARD can be used in a multitude of interior applications. KERDI-BOARD is not intended for exterior applications.