Fire Resistance of Natural Slate Roofing:
IBC Class A Fire Resistance Rating Received
The National Slate Association (NSA) and National Roofing Contractors Association (NRCA) recently teamed-up to conduct testing of the fire resistance of a slate roofing system in accordance with UL 790, “Standard Test Methods for Fire Tests of Roof Coverings.”
The testing was inspired by a change in the International Building Code (IBC), the 2009 edition of which recognizes slate roof assemblies as having a Class A fire resistance only when installed over a noncombustible roof deck. Previous editions of the IBC designated slate roof coverings as having a Class A rating when installed over combustible and noncombustible roof decks. The test assembly consisted of nominal 1/4-inch thick, North American slate shingles laid with a 3-inch headlap over No. 30 felt underlayment on a 1/2-inch plywood roof deck. The tested assembly achieved a Class A rating.
While it is hoped the favorable test results can be used to substantiate the fire resistance of similarly constructed slate roof assemblies, NSA and NRCA will continue to work together to exempt slate roof coverings from testing to determine their fire classification in future editions of the IBC.
- Complete details of the Slate Fire Resistance Test Report
For questions related to these test reports, please contact the National Slate Association toll free at 866-256-2111 or email mail@slateassciation.org.
Setting up the burning brand
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Burning brand test in progress. |
After the burning brand test. |
Close-up of the bottom of test deck after the burning brand test. |
These photos are posted with permission from Mark_S_Graham, see additional photos on Flickr.
