NASCLA Accredited Commercial General ContractorThermal and Moisture ProtectionEasy
A commercial building project specifies a roof system that must achieve a minimum fire resistance rating of Class A. Which roofing system is most appropriate to meet this requirement while also providing good durability and weather resistance?
- APolyvinyl Chloride (PVC) membrane
- BThermoplastic Polyolefin (TPO) membrane
- CBuilt-Up Roofing (BUR) system with a gravel surfacing
- DEthylene Propylene Diene Monomer (EPDM) membrane
Show answer & explanationAnswer & explanation
Correct answer: C. Built-Up Roofing (BUR) system with a gravel surfacing
Built-Up Roofing (BUR) systems, especially those with a gravel surfacing, are well-known for their excellent fire resistance and commonly achieve Class A ratings, along with good durability.
Why the other options are wrong
- A. PVC membranes offer good fire resistance but similar to TPO, might need specific assemblies or additives to consistently achieve a Class A rating.
- B. TPO membranes generally have good fire resistance, but may not inherently achieve Class A without specific fire-retardant additives or assemblies.
- D. EPDM membranes typically require additional fire-resistant layers to achieve a Class A rating, and are not inherently Class A on their own.
Roofing System Fire Ratings
Roofing systems are assigned fire resistance ratings (Class A, B, C) based on their ability to resist exterior fire exposure, as determined by ASTM E108 testing.
- Class A is the highest fire resistance rating.
- Ratings depend on the entire roof assembly, not just the membrane.
- Common tests include flame spread, burning brand, and intermittent flame.
Memory trick: Fire Safety Rules: Always Build Right for A-Class Protection.