This specification covers the standard for asphalt-saturated and coated organic felt base sheet with mineral surfacing on the top side, with or without perforations. These sheets are proposed for use as the first ply of a built-up roof and are also suitable for use as vapor retarder. The felt shall be manufactured principally from organic fibers, or mixtures thereof. The surface shall be smooth and uniform and reasonably free of lumps and particles of foreign substances. Physical requirements such as pliability, breaking strength, and water vapor permeance of the materials shall comply with the specifications prescribed herein.

1.1 This specification covers asphalt-saturated and coated organic felt base sheet with fine mineral surfacing on the top side, with or without perforations, for use as the first ply of a built-up roof. When not perforated this sheet may be used as a vapor retarder under roof insulation.

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