California Fire Rating For Decks

by John
(Napa Valley)

I heard that new decks in California have new fire standards they must meet and have to have certain burn rates?

Do know anything about this or where I can find out more? I am confused about what kind of decking material I should use to build me deck now.

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Sep 25, 2009
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Fire Ratings for Decks
by: Editor - Rich Bergman

Thanks for your question as it is relevant to California.

As of January 1, 2008 State Fire Marshal (SFM) standard 12 7A-4 was introduced to the California Building Code which sets out some pretty stringent fire rating standards for all newly constructed decks.

In order for a newly constructed deck to be code approved, it would have to still be intact and show no evidence of flaming or glowing 40 minutes after the burner used during the testing has been turned off.

In addition, in some cases where the decking material has a Class C flame spread, the walls of the home must be of a higher burn rating standard. This would require using traditional heavy stucco or cementitious fiber boards.

So any new deck you build would have to meet these standards. Since the regulations are so new it may not be easy to find materials that can meet this standard. And many products probably have not or may never be tested for this kind of application.

Most composite decking manufacturers have fire testing data and its called a flame spread index from 0-200. Zero is the best, 200 the worst. This standard for flame spread is ASTM E84.

Class A has a rating of 0-25, Class B is between 26 and 75, and Class C is 76-200

If you want to get a material approved you should contact the California Stat Fire Marshal and get a copy of standard 12 7A-4 and then hire an engineering firm to conduct the tests appropriately for review by the fire marshal.

There are some natural materials that have a class A fire rating which is on par with concrete and that is one of the exotic hardwoods known as Ipe. I am pretty sure that Ipe would last longer than any plastic composite material which would probably melt rather quickly.

Plastics in general have much higher heat release rates than wood and so the manufacturer would have to put fire retardants into the material and probably quite a lot. So I don't know if all of them do that or to what extent.

Although I do believe Trex has one product that has made it to Class B rating but please verify with Trex.

However what would you have to use for your joists?

That is a good question. You may have to use metal joists either of steel or aluminum. I am not sure what else is available.

But this means the cost of building a deck has just gone way way up because all of these materials are more expensive than common structural lumber.

But with all the brush fires in California over the years I suspect this is required.

Natural Fire Resistant Wood

For those who really do not want to go the composite route you might wish to take a closer look at Ipe.

It is so darn dense it is like steel and actually performs better than many composite materials.

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