This Standard covers asphalt saturated organic roofing felt, w ith or without perforations, for use in the membrane system of waterproofing systems and in the construction of built-up roofs using asphalt systems.
The following types of roofing felt are addressed by this Standard:
(a) Type 1 - a roofing felt that may be used in the construction of a built-up roof membrane (when perforated), as an underlay felt beneath asphalt shingles (when not perforated), or as a building wrap beneath brick, stucco, siding, etc. It is commonly called No. 15 felt;
(b) Type 2 - a roofing felt used as an underlay beneath asphalt shingles, wood shakes, tiles, and other sloped roof coverings. It is commonly called No. 25 or No. 30 felt.