This specification covers inorganic fiber-reinforced organic felt, and inorganic fiber-based asphaltic and nonasphaltic felt underlayments for use as underlayment with steep-slope roofing products. The intent of this specification is to provide criteria for producing and evaluating underlayments with a significantly reduced tendency to wrinkle before or after the installation of steep roofing products. Materials shall be sampled and tested suitably to examine their conformance with performance requirements such as tear strength, pliability, behavior on heating, liquid water transmission, dimensional stability at low to high humidity conditions, and elongation.

1.1 This specification covers (1) inorganic fiber-reinforced organic felt underlayment and (2) inorganic fiber-based felt for use as underlayment with steep-slope roofing products. The intent of this specification is to provide criteria for producing and evaluating underlayments with a significantly reduced tendency to wrinkle before or after the installation of steep roofing products.

1.2 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.

1.3 The following safety hazards caveat pertains only to the test method portion, Section 8, of this specification: 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 requirements prior to use.