Commercial Building Inspector B2Roof Ceiling ConstructionMedium
A contractor is installing a new roof covering system on a commercial building. The plans specify a Class A roof assembly. Which of the following roof coverings would typically meet the requirements for a Class A fire-resistance rating when installed in accordance with their listings?
- AAsphalt shingles over wood sheathing
- BSingle-ply TPO membrane over rigid insulation
- CClay or concrete roof tiles
- DUntreated wood shingles
Show answer & explanationAnswer & explanation
Correct answer: C. Clay or concrete roof tiles
Class A roof coverings are those that are effective against severe fire exposure. Clay or concrete roof tiles inherently provide excellent fire resistance and are typically rated as Class A. While some asphalt shingles and TPO membranes can achieve Class A with specific assemblies, clay/concrete tiles are universally recognized for this rating.
Why the other options are wrong
- A. Standard asphalt shingles often achieve Class A, but it depends on the specific product and underlying assembly, and are not inherently Class A without testing.
- B. Single-ply TPO membranes can achieve Class A, but usually require specific fire-resistant insulation or substrates, and are not inherently Class A on their own.
- D. Untreated wood shingles are typically Class C or unrated, not Class A.
Class A Roof Covering
A roof covering system that can withstand severe fire exposure, as determined by testing standards like ASTM E108 or UL 790.
- Highest fire-resistance rating for roof coverings.
- Required for many commercial buildings, especially those with higher fire hazard.
- Examples include concrete/clay tiles, metal roofs, and specially rated membrane systems.
Memory trick: Roof classes are like fire grades: A is the best shield.