What is the difference between Class A and Class B/C roof ratings, and how does this affect protection strategies?

• A. Class B/C roofs have the highest fire resistance
• B. Class A roofs are designed mainly for moisture resistance
• C. There is no difference between Class A and Class B/C roofs
• D. Class A is the highest fire resistance; use Class A or ignition-resistant roofs to maximize protection and minimize ember ignition risk

Answer: (D)

Roof ratings show how well a roof assembly resists wildfire exposure, including embers and radiant heat. Class A provides the highest fire resistance, meaning it resists flame spread and ember penetration better than Class B or Class C. Because embers are a leading cause of roof ignition in WUI fires, using a Class A roof—or a roof that is ignition-resistant—greatly reduces the likelihood of the roof catching fire and spreading to the structure. That’s why the best protection strategy is to install Class A roofs or ignition-resistant roofing materials, ensuring proper installation and maintenance to keep gutters, debris, and vents clear and ember-proof. If a Class A roof isn’t feasible, an ignition-resistant roof still offers better protection than lower-rated options, but the highest level of protection comes from Class A. The other statements don’t reflect the true differences in fire resistance or the protective goal of minimizing ember ignition.