This specification covers the standards for polymer modified bituminous sheet materials proposed for use as underlayment on roof eaves, or valleys, or both, to prevent leakage of shingle, tile or metal roofs from water back-up due to ice dams. The underlayment sheet shall comply with the physical requirements which include thickness, maximum load, elongation, adhesion to plywood, thermal stability, flexibility, tear resistance, moisture vapor permeance, sealability, and slip resistance. The underlayment sheet shall not crack, as well, nor be too sticky as to cause damage upon being unrolled.

1.1 This specification covers polymer modified bituminous sheet materials intended for use as underlayment on roof eaves, or valleys, or both, to prevent leakage of shingle, tile, or metal roofs from water back-up due to ice dams.

1.2 These underlayment sheets have a sticky adhesive layer which is exposed by removal of a protective sheet. The top surface is suitable to work on during the application of the exposed roofing.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.