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R311.2.2 2006 IRC Under stair protection

Yankee

Yankee

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Mar 31, 2010
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During a C.O. inspection yesterday I came across an under stair closet (enclosed accesible) which had been finished out with cedar as a cedar closet. In order to approve or dissapprove an alternative means of compliance, I want to check my understanding of why the code calls for 1/2" gyp board on the interior of such a space. The gyp board would be to provide 15 minutes of fire protection to an egress stairway, correct? Or is there some other reason?
 
Yankee said:
The gyp board would be to provide 15 minutes of fire protection to an egress stairway, correct? Or is there some other reason?
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My understanding of it is pretty much the same as yours. The gypsum board prevents a fire that may start in the storage space from compromising the use of the stairway for a little while longer.

Was there gypsum board under the cedar finish?
 
No, plywood under the cedar. I told him if he could show 15 minutes with the assemblys applied, that would be an acceptable alternative.

My other thought is (and this is why I've posed for comments): if an additional hard wired smoke was installed under there, wouldn't that meet the intent of the gyp-board (provide early warning to use those stairs)?
 
It might be simpler to remove the cedar, install 1/2 gyp, then reinstall the cedar. They obviously installed all this wood without knowing (or applying) the code. The addition of a smoke detector is an interesting idea. I suppose that would be the call of the building official (unless you are it).
 
Glennman CBO said:
It might be simpler to remove the cedar, install 1/2 gyp, then reinstall the cedar. They obviously installed all this wood without knowing (or applying) the code. The addition of a smoke detector is an interesting idea. I suppose that would be the call of the building official (unless you are it).
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Yaaaa . . . I'm "it" all right . . . : )

The under stair is also "under landing" (crawl height for storage) and would be quite difficult to re-do.

thanks
 
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How thich are the cedar boards? They might be sufficient as the flame barrier alone.
 
i know its not IRC but IBC 721.6.2.2 time assigned to membranes. table 721.6.2(1) indicates the time assigned to membranes on the fire exosed side.

721.6 is wood assemblies. FWIW... plywood with cedar over you may decide you can accept that as a 15 minutes.
 
88twin said:
i know its not IRC but IBC 721.6.2.2 time assigned to membranes. table 721.6.2(1) indicates the time assigned to membranes on the fire exosed side. 721.6 is wood assemblies. FWIW... plywood with cedar over you may decide you can accept that as a 15 minutes.
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Yes, if the assembly added up to 15 or more I would, and I did leave that as an option and now I'll go look at the section you quoted, thanks!
 
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