# Separation between B & S occupancies



## svey (Feb 5, 2010)

Does anybody know the rationale behind requiring a fire-rated separation between B & S-2 occupancies but not between a B & a more hazardous S-1 occupancy based on Table 508.3.3?


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## Coug Dad (Feb 5, 2010)

Re: Separation between B & S occupancies

Welcome to the site.  This has been discussed before.  For a B /S-2 configuration, you are actually protecting the low hazard storage from the more hazardous business, not that the logic makes a lot of sense.  You can search the postings for other learned opinions.


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## brudgers (Feb 5, 2010)

Re: Separation between B & S occupancies

S-1 is low hazard by definition.

Business is moderate hazard (or ordinary hazard under NFPA).

If you want to avoid the separation, classify the storage as S2.


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## Coug Dad (Feb 5, 2010)

Re: Separation between B & S occupancies

Brudgers,  I think you have your S's backwards


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## Gene Boecker (Feb 5, 2010)

Re: Separation between B & S occupancies

And, of course, all this is based on the assumption that a separation is desired rather than using the non-separated option in the code (Section 508.3.2 in the 2006 IBC).


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## Big Mac (Feb 5, 2010)

Re: Separation between B & S occupancies

depending on the size of the building non-separated use might not be an option.  The premise behind the code is that when separations are required the less hazardous occupancy needs to be separated and protected from the more hazardous occupancy.  Based on separation requirements found in Table 508.3.3, one has to assume that the code considers the 'Use Group B' occupancies and the 'Use Group S-1' occupancies to be on an equal footing with regard to hazard.  Conversely the code considers the 'Use Group S-2' occupancy to be less hazardous than the 'Use Group B' and therefore needs a fire resistive protection for the S-1.


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## Gene Boecker (Feb 5, 2010)

Re: Separation between B & S occupancies



			
				Big Mac said:
			
		

> depending on the size of the building non-separated use might not be an option.  The premise behind the code is that when separations are required the less hazardous occupancy needs to be separated and protected from the more hazardous occupancy.  Based on separation requirements found in Table 508.3.3, one has to assume that the code considers the 'Use Group B' occupancies and the 'Use Group S-1' occupancies to be on an equal footing with regard to hazard.  Conversely the code considers the 'Use Group S-2' occupancy to be less hazardous than the 'Use Group B' and therefore needs a fire resistive protection for the S-1.


Ah, but if the building is big enough (huge S-2) then the Business portion could be possibly less than 10 percent of the overall and considered an accessory occupancy - even better!

Weird how this code thing works sometimes. . . . .


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## RJJ (Feb 5, 2010)

Re: Separation between B & S occupancies

Gene: I would assume you are referring to a small office attached or inside a much larger storage area! To use the % theory.


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## Gene Boecker (Feb 5, 2010)

Re: Separation between B & S occupancies



			
				RJJ said:
			
		

> Gene: I would assume you are referring to a small office attached or inside a much larger storage area! To use the % theory.


Exact-amundo!


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## svey (Feb 8, 2010)

Re: Separation between B & S occupancies

Thanks for the insight guys.  Although it's going to take some time to recalibrate my thinking about what we're trying to protect in this particular case, the table does seem to imply the protection is for the occupants in the S-2 occupancy from the more hazardous B occupancy.  Thanks again guys.


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