1.1 This specification covers asphalt impregnated and coated glass fiber base sheet, with or without perforations, for use as the first ply of the built-up roofing. When not perforated, this sheet may be used as a vapor retarder under or between roof insulation with solid top coating of asphaltic material.

1.2 The values stated in inch-pound units are to be regarded as the standard.