Underlayment earns Class A fire rating for broader roofing applications

By Jesse Sanchez. 

Contractors gain expanded fire-rated assembly options across metal, tile and asphalt systems. 

Roofing contractors have new flexibility in meeting fire-resistance requirements as MFM Building Products announces a Class A fire rating for its Ultra HT Wind and Water Seal® underlayment across multiple roofing systems. The designation expands its use in projects where fire performance is essential, including commercial, architectural and select residential applications. 

Designed for steep-slope roofing and re-roofing, Ultra HT is a 45-mil, self-adhered underlayment built to perform under demanding conditions. A cross-laminated polyethylene top film paired with a traction coating supports durability and jobsite safety, while a high-temperature mastic rated up to 250°F allows installation beneath metal and tile systems where heat exposure is a concern. 

The fire rating applies across a range of assemblies, giving contractors greater material flexibility. Under UL 790, the product is listed as a Class A fire-resistant barrier when used with 24-gauge minimum steel or 16-ounce copper UL-listed roofing panels. It also meets Class A performance requirements with standard three-tab and architectural asphalt shingles under ASTM E108 and ICC-ES AC188. Together, these classifications allow contractors to maintain fire-rated performance without limiting system selection. 

In addition to fire resistance, Ultra HT is designed to strengthen the overall roof assembly. The membrane adheres directly to the roof deck and seals around fasteners, helping reduce the potential for water intrusion. Its high elongation accommodates building movement, while the non-slip surface improves footing during installation. The underlayment is also compatible with a variety of substrates, including plywood and metal. 

The product has been tested and approved under multiple standards, including ASTM D 1970, Florida Building Code, Miami-Dade County approvals, ICC-ES ESR-1737 and Texas Department of Insurance listings. It carries a 10-year warranty and is manufactured in the United States. 

For contractors, the expanded Class A rating positions the underlayment as a reliable option for meeting code requirements while reinforcing long-term roof performance. 

Learn more about how Class A fire-rated underlayments can expand roofing system options while supporting code compliance and long-term performance!