CertainTeed Glasbase Base Sheet is designed for use as a base sheet for both hot and cold applied, inorganic built-up roofing systems. It is suitable for use in the construction of various types of membranes for both new construction and reroofing, over a variety of substrates. In addition, it will perform as a venting base sheet when spot mopped over plastic foam type insulations. Glasbase Base sheet will provide additional strength, moisture resistance and asphalt uniformity when used as the first ply over nailable, non-nailable and insulated substrates.