A Class A vs. Class C Fire Rating

Whether you are a homeowner or a business owner looking for a new roof, you might have noticed that some roofs are classified as Class A or Class C.  You might not know what the difference is however.

Class A and Class C are defined by a non-for-profit independent testing agency known as Underwriters Laboratories or UL.  It was founded in 1894.  Many products have UL certifications because UL tests for public safety and when a product achieves a UL rating it is then more marketable. 

The class rating (A, B, or C) given to roofing products that have been tested are named after the size of the "burning brand" that is placed on the roof during the fire test.

The Burning Brand Sizes Are As Follows:

  • Class C - 1" x 1" Burning Brand
  • Class B - 6" x 6" Burning Brand
  • Class A - 12" x 12" Burning Brand

The brand is first lit exposing each edge and face to the flame for 30 seconds. 

If the burning brand is able to burn through the bottom of the deck or if the heat transfer is enough to result in ignition on the other side of the deck, then the roof covering or assembly (roof covering and underlayments) fails the test.  If they fail the test, then they do not get a rating.

For great visuals of how these tests work, you might be interested in a presentation that Steve Quarles put together at the University of California at Berkley.  You can also watch our video on YouTube of a simulated Class A Burning Brand on our Synthetic Cedar Shake shingles compared to natural shake shingles:

Sometimes the roofing products (like the shingles) are not a Class A system by themselves.  In order to be a Class A system, they have to have an appropriate underlying fire barrier to achieve the Class A assembly.

If you want a green roof construction product that holds up to a Class A standard, then you will want to check out our environmentally friendly roofs - DaVinci Products.  

Learn more about DaVinci by talking to a DaVinci product specialist.


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