October 15, 2015
IBC 2018 Section 508.3 is for Non-Separated Occupancies, 508.4 including T 508.4 is for Separated occupancies. You have the choice of which to follow as designer. If you follow the non-separated 508.3 than you do not have to use the table T508.4 but you must follow the most restrictive requirements for the occupancy classifications for the building area. For example, B with an F-2 . VB construction non sprinklered, T602 will indicate B is allowed max 9000 sqft area and F-2 is allowed 13000 sqft. The rule will be the B occupancy because its most restrictive. This is how you would go through all requirements that are specific to the occupancy classification in the code. You could be bouncing back and forth between B and F-2 requirements. If your building area is less than 9000 sqft you will not need a Fire wall/barrier/partition.
If you choose to follow separated occupancies than yes you would follow T508.4 requirements. But don't mix the 2 sections. Keep them separated
October 17, 2019
I am working on an existing foundry. We are proposing to demolish their office portion and build a new envelope with new offices. I read on 508.2.4 that no separation is required between accessory occupancies and the main occupancy. Then I go to 508.3 It says no separation is required between non-separated occupancy. Following that there is 508.4 table that tells you which occupancies need to be separated. The main building is F-2 and I have a B occupancy that is an accessory space (is less than 10% of the entire building). In that table it says that 2 hr is needed between B and F-2 for a non- sprinklered building.
I was thinking that because it is an accessory space that no separation was required but on 508.4 says otherwise. I am trying to understand how to interpret the code to decide if I need a 2hr fire barrier between occupancies.
Thanks in advance!