Understanding Roof Fire Ratings

It is important for homeowners to be aware that roofs have different fire rating classifications. They are rated as manufacturers submit samples of their roofing products to a certified testing laboratory for certification. These undergo tests that determine a material’s fire resistance. Roof and door installation contractors from Abby Windows enumerate them below.

1. Unrated Roofing means it could not pass even the requirements for Class C roofing materials. This type of roofing provides little fire resistance and should be avoided. Understand that most building codes will not accommodate any type of unrated roofing material.

2. Class A roofing is the preferred choice for any home yet it is specifically vital if you live in an area that is prone to wildfires. To achieve a Class A rating, the roof must be effective against severe fire exposure. This is proven if it can experience the maximum flame spread of 6 feet and resist 15 cycles of a gas flame turned on and off. It should be able to withstand a burning brand measuring 12 by 12 inches and weighing 2000 grams and last one hour before ignition.

3. Class B roofing is effective against moderate fire exposures. Roof and siding contractors note that the maximum flame spread should be 8 feet. It should be able to withstand a burning brand measuring 6 by 6 inches and weighing 1.1 pounds, last one hour before ignition, and can resist eight cycles of a gas flame being turned on and off.

4. Class C roofing provides light fire protection. This normally applies to untreated wood shakes and shingles, plywood, or OSB. The maximum flame spread should be 13 feet. It should be able to withstand a burning brand measuring 1.5 by 1.5 inches and weighs 0.009 ounces, last 20 minutes before ignition and can resist 3 gas flame cycles.