... ''X72' 30# ASTM D226,36''X72' building material Asphalt roof felt ASTM D-4869 30# Description: A heavy-weight asphalt roofing ... felt of building material made of a specially formulated organic sheet ... has been fully saturated with waterproofing asphalt. Uses: A roofing felt used as an underlay beneath asphalt shingles, wood shakes, tiles ...