BK-Dur, waffl e is a thermal insulation board made of extruded polystyrene foam with a ribbed surface structure, resistant to water (moisture) and high pressure loads. It is intended for insulation of new buildings and renovation of existing buildings. Hard-pressed polystyrene foam boards with a closed-cell structure allow the building to “breathe.” This is achieved by a special mixture and composition of cells in combination with the treated surface. It is used for insulation of foundations, insulation of floors with high pressure load, perimeter insulation, and insulation of flat roofs.