GlasBase™ Base Sheet is CertainTeed's workhorse, non-modified base sheet, suitable as a starter course under BUR ply sheets or modified asphalt cap sheets applied with a torch, hot asphalt, or cold adhesive such as FlintBond® Brush. This 40 mil permeable base sheet is manufactured with a strong, dimensionally stable fiberglass reinforcement. GlasBase is most commonly mechanically attached but may serve as a non-penetrated base ply when mopped with hot asphalt or FlintBond® Brush cold adhesive. In addition, it will perform as a venting base sheet when spot mopped over plastic foam type insulations. Reach out to your local CertainTeed Territory Manager to request a sample and demonstration of GlasBase Base Sheet.