1.1 This specification covers asphalt-impregnated and coated glass-fiber base sheet with mineral surfacing on the top side and coarse mineral granules on the bottom side for use as the first ply of a roofing membrane. These base sheets prov This specification covers the manufacture and requirements of Type II heavy-duty asphalt-impregnated and coated glass-fiber venting base sheet with mineral surfacing on the top side and coarse mineral granules on the bottom side for use as the first pl