This specification covers prefabricated modified bituminous sheet materials with polyester fabric reinforcement, with or without granules, that use atactic polypropylene (APP) as the primary modifier and are intended for use in the fabrication of multiple ply roofing and waterproofing membranes. This specification is not intended for (1) issues regarding the suitability of specific roof constructions or application techniques and (2) in-place roof system design criteria such as fire resistance, field strength, impact/puncture resistance, material compatibility, uplift resistance, the need for field applied coatings, and others. Type I and II modified bituminous sheet materials reinforced with polyester fabric, with granule surfacing (Grade G) and smooth surfacing (Grade S) are covered by this specification The APP modified bituminous coating shall be permitted to be compounded with a mineral stabilizer. To prevent sticking in the roll, the reverse side and any selvage shall be permitted to be covered with a fine mineral surfacing or any other surfacing that will not interfere with adhesion or bonding of the lap. The sheet shall conform to the minimum physical properties prescribed for: peak load, elongation, ultimate elongation, tear strength, low temperature flexibility, dimensional stability, compound stability, granule embedment, water absorption, moisture content, and low temperature unrolling. The finished product shall conform to the requirements prescribed for net mass and dimensions such as width of roll, area of roll, selvage width, thickness, and bottom side coating thickness. The specified ultimate elongation, high temperature stability, and low temperature unrolling test methods shall be used.