Your Roof: Fire Resistance and Fire Ratings Explained
Every summer sees its share of devastating wildfires threatening or consuming residential developments. But, if there’s any glimmer of hope from these tragedies, building science is developing better fire-safe ways to build homes. In particular, scientists have devoted effort to keep burning embers from entering homes through air vents, soffits, and walls. And, of course, fire-safe roof and wall products are important too.
Over the years, when discussing fire resistance, I have always made the distinction between interior and exterior fires. The same products that make the roof of a home resistant to external fires make it difficult for an interior fire to burn its way through and self-vent. When a fire inside a building can’t burn through the roof, it spreads laterally, consuming more of the building and contents.
Fire Resistance and Ratings for Metal Roofing
When it comes to fire ratings and metal roofing, the higher melting point of copper and steel leads to a naturally higher fire rating. With aluminum, special fire-resistant underlayment must be used for a Class A or Class B rating. But even with a standard underlayment, it’s still a non-combustible roof surface. The lower melting point of aluminum with a standard underlayment can protect against many exterior threats. However, it will still allow an interior fire to burn through and vent.
The low weight of metal roofing is an added benefit when it comes to fire resistance. Most roofing materials are much heavier than metal. These materials can pose a significant cave-in threat in the event of an interior fire. In worst cases, when the roof collapses, firefighters can only contain the fire from the outside rather than go inside and extinguish it. A low-weight roof can help prevent collapses. The weight of aluminum roofing is a half-pound per square foot, compared to one pound for steel, three pounds for asphalt shingles, and twenty pounds for tile.
There are several key steps you can take for fire safety. Some are dictated by building code, and others are personal preference. I frequently talk to architects and property owners in their quest for fire safety. I’m here to help, so please feel free to contact me at any time.
Todd Miller has spent his entire career in the metal building products manufacturing industry. He is president of Isaiah Industries, an organization recognized as one of the world’s leading metal roofing manufacturers. Todd is currently Vice President of the MRA (Metal Roofing Association) and a Past Chair of MCA (Metal Construction Association). Through his website, he strives to raise the bar on standards and practices to provide property owners with the best possible products for successful roofing projects.
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