Nonseparated occupancies in existing buildings.

I'm working on an existing mixed use (B, A3) 3-story building with a new A3 occupancy group (occupant load=106) on the 2nd floor. Being between floors, the required horizontal occupancy separations would be a problem. However, the building complies as a non-separated occupancy..based on A3, type III-A, sprinklers, and frontages.


I've heard back from our plan checker, and their opinion is that we need to bring the entire building up to 2007 CBC (based on the 2006 IBC) requirements. Additionally, they say we need to check the structural calcs for the whole building since they say we are changing to occupancy category III (per IBC chapter 16).

My stance is that chapter 508.3.2 is not meant to change the occupancy or construction of the building- it's only a tool to provide an alternative to separated occupancies if certain criteria are met.

Can anyone shed some light on this issue?


thanks,

Greg
Original Post
If you are changing the occupancy category to III then per section 3406.4 you need to conform to the seismic requirements for a new structure (there a some exceptions).
However, your occupant load is less than 300 and you are still under occupancy category II (See CBC table 1604.5).
Thanks for the reply. My main question is whether using the nonseparated option (in this case A3 vs a mixed occupancy) should result in all the same requirements as actually changing the use of the building.

Also- re the cat. III requirements- table 1604A.5 states: "covered structures whose PRIMARY occupancy is public assembly with an occ. load grater than 300. I read that to mean you can still have a load over 300 (and maintain category II) in a mixed use building, so long as its primary occupancy is not public assembly.

thanks,
Greg
Using the nonseparated uses method to determine code compliance with Group A-3 being the most restrictive would not trigger a change of occupancy IF the existing building currently includes a Group A-3 occupancy.

Regarding the Category III application, here is what the IBC Code and Commentary has to say:

"The revised wording requires agreement on the determination that a building’s 'primary occupancy' is in fact public assembly. This could be as simple as verifying that the portion of the building housing the public assembly occupancy is more than 50 percent of the total building area. Also, the previous wording referred to the occupant load of 300 in 'one area.' Since the reference to one area has been dropped, it would now appear that the aggregate occupant load of all the public assembly uses would be used in making this determination."

Therefore, the occupant load limitation is applied to the total occupant load in all of the Group A occupancies. But, if the primary purpose of the building is not assembly (50% by the Commentary's definition), then this item would not apply.
Likes (0)
×
×
×
×
×