Firestone Venting Base Sheet consists of an oxidized asphalt compound reinforced with a nonwoven, glass fiber mat & surfaced with factory-applied ceramic granules on the underside to aid in underside venting. Firestone Venting Base Sheet has a light coat of sand on the top surface. The roofing membrane can be applied to the mechanically attached Venting Base sheet by conventional hot asphalt, Firestone MB Cold Adhesive or by use of a roofing torch. It is designed to be mechanically fastened over lightweight concrete roof decks as a base for a Firestone modified bitumen or built-up asphalt roof system.