# Fire Barrier Conversion



## DTBarch (Apr 30, 2014)

I apologize in advance for what is likely a redundant question in the Forum.

Scenario: Existing fully sprinklered warehouse building in California.  Formerly B and S-1 occupancies.  New tenant is using warehouse space as an S-2 occupancy.  Wall separating office from warehouse was originally built as a non-rated wall with 5/8" type x full height to deck on warehouse side, but with gyp. only to 6" above grid on office side.  With new S-2 use, we need a 1 hour barrier.  Exposed studs above ceiling on office side have multiple conduits attached, and of course easy access is restricted by existing ceiling grid.  I assume that the exposed studs on the office side prevent compliance with CBC Section 703.2.1 for non-symmetrical wall construction.

Question:   Is there an assembly solution available that would allow existing warehouse side full-height type x gyp board to act as one side of new 1-hour rated fire barrier?  Since you can't fasten through that side into the new studs, I'm unclear if there's any possibility there.  If not, in your experience have you seen this solved in a efficient manner?


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## cda (Apr 30, 2014)

Build a new one hour wall on the warehouse side

Look also at the build your own rated wall in ibc, will try to find the section

721 2009 ibc


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## DTBarch (Apr 30, 2014)

Yes, but can I use the existing warehouse side gyp. board as the inside gyp. board barrier of my new 1 hour wall?  In other words, butt new studs to existing wall and add one new layer of 5/8" type x? Remember, the backside of that existing rock is exposed above the ceiling line on the other side...


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## FM William Burns (Apr 30, 2014)

If you can't treat or repair the exposed side above the office area, the construction of a new listed assembly on the new tenant side is all I can envision.


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## cda (Apr 30, 2014)

DTBarch said:
			
		

> Yes, but can I use the existing warehouse side gyp. board as the inside gyp. board barrier of my new 1 hour wall?  In other words, butt new studs to existing wall and add one new layer of 5/8" type x? Remember, the backside of that existing rock is exposed above the ceiling line on the other side...


Unless missing something do not see why not

If it was built new it would still be exposed, as long as thickness and every other spec for the Sheetrock is correct


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## steveray (Apr 30, 2014)

No listed assembly that I can think of for backwards drywall not fastened to the rated wall....Maybe you can prove something with equivalancy from Chapter 7?  You can't do mixed use nonseparated? No reduction for the sprinklers?


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## cda (Apr 30, 2014)

"""Since you can't fasten through that side into the new studs,""""

Missed that

Hang from the rafters, scaffold, ladder some means to get it fastened ??

How many sq ft are you talking about??

Just throw up another complete one hour wall against the existing wall, and don't mess with the existing

Use densglass assembly ?

http://www.westsidebmc.com/common/getfile.aspx/176641

http://www.buildgp.com/DocumentViewer.aspx?repository=BP&elementid=4286


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## mtlogcabin (Apr 30, 2014)

What code section requires the rated separation?

Is the office accessory to the S-2 warehouse?

In other words

Find the charging language that requires a rated separation and if there is one then look at the other options available.

Non-separated uses

Accessory uses


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## Francis Vineyard (Apr 30, 2014)

Following mtlogcabin analysis seems it may not need to meet all the separation requirements; see 3408.1


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## DTBarch (May 15, 2014)

Interesting and useful comments gentlemen.

So check this out.  The subject space occupies 66,536sf of an unlimited area Type IIIB warehouse building with a total area of around 180,000sf.  As mentioned, the two occupancy groups involved in this tenant space are B and S-2.  Table 508.4 of the CBC requires a 1 hour separation between B and S-2.  Since the office area occupies 8,761sf, we can not use the accessory use exemption (over 10%).  Therefore, per mtlogcabin's suggestion if we explore non-separated occupancies per Section 508.3 we identify the most restrictive of the two occupancies to be the Group B occupancy, which under Table 503 has a tabular limit of 19,000sf for the Type IIIB category that it is in (versus 26,000sf tabular for S-2).  Applying the building area modifications in Section 506 we have the tabular base of 19,000sf PLUS a frontage increase of 9,918sf PLUS a Fire Sprinkler increase of 38,000sf results in 19,000 + 9,918 + 38,000 = 66,918sf allowable versus our actual overall area of 66,536sf.

Here's the base data for the calculation:

Tabular Area: 19,000sf

Frontage exceeding 20' = 821'

Total Perimeter = 1063'

Sprinkler Increase Factor is 2 for AFES

So it appears as though we would be just barely under the limit and exempt from the 1 hour separation requirement.  Is there anything I'm missing or not calculating correctly?

I know Section 508.3.1 references most restrictive applicable provisions of Chapter 9.  Are there any typical pitfalls in there that I need to watch out for??  Chapter 9 is such a far reaching chapter and seems like there could be some boogey men in there, or am I just paranoid?

As always, greatly appreciate your suggestions.  Have often used non sep calcs for single tenant buildings, but never applied it to "portions of" as made available by 508.3


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## DTBarch (May 15, 2014)

After review, I see a couple mistakes in my calc.  Specifically with the frontage factor should use 9,923 instead of 9,918 and the sprinkler factor is 3, not 2 for the one story condition.  Both of which increase the allowable and make it not so close, and still seemingly resulting in relief from the separation requirement.


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## Francis Vineyard (May 15, 2014)

A designer may choose a fire barrier separation but it would not be required where non-separated is applicable.


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