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Existing Building - Mixed Occupancies
May 18, 2020
7:38 pm

Forum Posts: 4
Member Since:
March 1, 2019
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Sounds correct to me using IBC 2018 second edition 

508.4 will walk you through… or if it’s used with an occupant load of Less than 50 then you can use the same use. 303.1.2 #1

im not a code official or a building inspector yet, been studying IBC 2018 and passed my exams.

im just brushing up and taking on some of the interesting topics. 

Im looking forward to plan review 

anyway good luck


May 18, 2020
4:26 pm
New Member

Forum Posts: 1
Member Since:
May 18, 2020
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Question about if I am interpreting Mixed Occupancy Code correctly – scenario:


2012 IBC

Building is existing, from 1981, 4 Stories, 49,000 SF, 4 identical floors (12,250 SF per floor).  II-B Construction (unprotected steel frame w/ concrete floors in metal deck).

Building was retrofitted with a sprinkler system at some point, and flanks two major roadways and has a third open side thanks to a wide access driveway (thinking 504.2 and 506.2 here).

Building was originally 100% B Occupancy, but we will introducing Assembly Occupancy on three of the floors, to be as follows:

4th Floor – 12,250 SF B Occupancy, 0 SF A-3 Occupancy (unchanged)

3rd Floor – 7,750 SF B Occupancy, 4,500 SF A-3 Occupancy

2nd Floor – 10,250 SF B Occupancy, 2,000 SF A-3 Occupancy

1st Floor – 7,750 SF B Occupancy, 4,500 SF A-3 Occupancy


Because our A-3’s exceed the 10% threshold outlined to be an Accessory Occupancy, we would need to address them as a Separated Occupancy a la 508.4, correct?


It’s my understanding we would not qualify for a Non-separated Occupancy since our overall building already exceeds what the strictest limits would be (imposed by the A-3), even though our A-3 only extends up three stories and individually and A-3 floor areas don’t exceed their individual limits.


We would love to get away with doing Non-separated Occupancy as a matter of design flexibility and affordability, but are prepared to separate if needed.  I think I’m overthinking this like I have seen others do on assorted building code forums…


Thanks in advance!