This specification covers the standards for asphalt impregnated and coated glass fiber base sheet intended for use as the first ply of built-up roofings. This sheets are also suitable for use as a vapor retarded under roof insulation or between multiple layers of roof insulation. The materials shall conform to the physical requirements, dimensions, and masses prescribed herein. The products shall not crack nor be too sticky as to cause damage upon being unrolled. The specimen shall also undergo testing to determine the following properties: breaking strength, moisture content, and pliability.