GAP Fiberglass Base G2 sheet is manufactured from tough inorganic Fiberglass mat then coated on both sides with weathering grade coating asphalt and then covered on top with white sand fines to prevent sticking in the roll. GAP Fiberglass Base sheet is applied over the flat roofing deck or insulation as a Base Sheet by Mechanical Fasteners or Hot Asphalt before the application of Build-Up Roofing systems. This sheet is suitable as a vapor retarder, with a solid mopping of asphaltic material, under roof insulation or between multiple layers of insulation.