# Proper use of CBC/IBC table 508.4



## Joe.B (Feb 18, 2021)

This table has the same occupancy types listed across the top and down the sides and for the most part makes sense. I'm confused about the discrepancies when you get to H occupancies. If I go down to H-3/H-4 then over to H-1 a 1 hour separation is required if the building is sprinklered. If I go over to H-3/H-4 then down to H-1 it's NP, not-permitted. If I go down to H-5 then over to H-2 then no fire rating required if it's sprinklered. Over to H-5 then down to H-2 1-hour rating is required. Do you always go over first, then down? Does this imply, for example, that if you are designing or working on an H-2 (sprinklered) with an H-5 next door then no separation required on your side. If you are on an H-5 (sprinklered) job with an H-2 next door then you are required to do a 1-hour wall? Thanks!


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## cda (Feb 18, 2021)

Down first

Than over


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## RLGA (Feb 20, 2021)

Actually, go whichever way you get a value. If you use it and get a "—," then you used it the wrong way.


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## cda (Feb 20, 2021)

Ok,,, there are two ways to read a table


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## Joe.B (Feb 22, 2021)

RLGA said:


> Actually, go whichever way you get a value. If you use it and get a "—," then you used it the wrong way.


That's what I thought it should be. It turns out CA decided a simple chart wouldn't be good enough, they had to throw a wrench in it. 

So anybody from California want to take a stab at this? Down then over, or over then down?


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## cda (Feb 22, 2021)

Joe.B said:


> That's what I thought it should be. It turns out CA decided a simple chart wouldn't be good enough, they had to throw a wrench in it.
> 
> So anybody from California want to take a stab at this? Down then over, or over then down?



Cannot copy and paste it

but this table 508.4????







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I like go down first than over ??

Are we missing something ???


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## Joe.B (Feb 22, 2021)

The link you provided is what I'm looking at. Down first then over appears to be the less restrictive approach, which is what has me worried. Generally when there are conflicts the "more restrictive provisions shall apply". I was wondering if anybody else has had this come up in review. I see two possible interpretations: Go with more restrictive = go over then down in all cases. Or top row is occupancy in question (review/approval), side column is adjacent occupancy. Thanks for taking the time to consider this apparent conflict.


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## RLGA (Feb 22, 2021)

California broke the system. Apparently, somebody did not think it through.


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## cda (Feb 22, 2021)

Looks like for California

You read across first

Than down


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## Joe.B (Feb 23, 2021)

RLGA said:


> California broke the system. Apparently, somebody did not think it through.


Must be all the earthquakes... or the weed.


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