Underwriters Laboratories, Inc (UL) is the most well-known independent safety certification company. They use three classes to rate how fire-retardant roofing materials are. Residential roof contractors in St. Charles, MO, uses these categories also.
These classes are:
Class A – Least Flammable
- Maximum flame spread of six feet
- Withstand up to a 12′ x 12′ burning brand weighing up to 2kg
- Two to four hour ignition time
- Resists 15 cycles gas flame cycles
Asphalt with fiberglass underlay, clay, and slate are examples of Class A roofing materials.
Class B – Semi-Flammable
- Maximum flame spread of eight feet
- Withstand up to a 6′ x 6′ brand up to 500 grams.
- One-hour ignition time
- Resists eight cycles gas flame cycles
Shakes and shingles fall under the class B category.
Class C – Barely Fire-Retardant
- Maximum flame spread of 13 feet
- Withstand a 1.5″ x 1.5″ brand up to 1/4 of a gram
- Twenty-minute ignition time
- Resists three gas flame cycles
Untreated shakes, shingles, and plywood all fall under this category.
If a roof material isn’t rated, you may as well be using paper.
Now that you know about the different classes to rate how fire-retardant certain roofing materials are, you can make more informed decisions. Affordable Exteriors are a premier residential roof contractor in St. Charles, MO, with the best roof material options.