All kinds of roofing systems are expected to meet or exceed requirements set forth by building codes and insurance providers, one of which is fire resistance. Local roof service company Fields Roof Service shares a quick guide to residential roof fire ratings.
How Are Roofs Rated?
Roofing manufacturers submit samples of their products to certified testing laboratories like UL Inc. and FM Global in order to obtain fire rating and certification. The samples undergo tests under guidelines and conditions defined in ASTM E108 – a set of standards designed to determine a product’s fire resistance. Some of these tests include exposure to open flame, direct exposure to gas flame, and pressing a burning brand to simulate embers from a neighboring fire.
Data from factors such as flame spread and the time it takes before the product catches on fire are recorded and used to determine the fire rating. The same data can also be used by the roofing manufacturer when designing roof repair and maintenance methods for their products.
Roof Fire Ratings
Roofing products that pass the tests can be classified into three ratings depending on how they perform:
- Class A roofing products provide the best protection from fires caused by external factors like wildfires. To qualify for a Class A rating, the roofing product must allow a maximum flame spread of 6 feet, must ignite between 2 and 4 hours after contact with a 12-by-12-inch burning brand weighing 4.4 pounds, and must resist 15 cycles of exposure to a gas flame. Slate, tile, and metal roofs generally receive a Class A rating due to natural flame resistance.
- Class B rating is applied to roofing products that allow the flame spread of up to 8 feet, ignite after 1 hour of contact with a 6-by-6-inch, 1.1-pound burning brand, and resist 8 cycles of gas flame exposure. Most standard asphalt shingles receive this rating, which can be augmented with specially-designed products like GAF VersaShield® Fire-Resistant Roof Deck Protection.
- Class C roofing products provide a bare minimum of fire protection. This rating is applied to roofing products that allow up to 13 feet of flame spread, ignite after 20 minutes of contact with a 1.5-by.15-inch, 0.009-ounce burning brand, and resist 3 cycles of exposure to a gas flame. Wood roofing, including untreated wood shakes, fall in this category. Roofing products that fail Class C standards are considered Unrated and are unsuitable for use on occupied buildings.
For more information about fire-resistant roofing or other roofing products and services, call Fields Roof Service at (253) 852-4974. You can also fill out our contact form to schedule an appointment.
