One of the oldest and most versatile construction materials, mastic asphalt is widely used in building construction and civil engineering as a sealing and wearing surface. Specially adapted mixtures of bitumen and fillers are applied hot, either mechanically or manually. Mastic asphalt screeds are gas-tight and provide effective protection against radon. They can be laid on critical subfloors such as old wooden floors or directly on ground-bearing substrates and are fully usable after approximately six hours of cooling.