Occupancy category - IBC 2009 vs ASCE 7-05

[jittles]

Hello fellow engineers, I am in need of some second opinions on a potentially sticky code interpretation issue.

This is in the U.S., governed by IBC 09.

What occupancy category would you assign to the following structure?

Two story steel framed building. The first story consists of two small, one-story restaurants on each end (occupancy load = ~30 each). In between these, there is a workout facility/gym that is two stories (first floor occupant load = 129, second = 160).

The two restaurants and the gym in between are not connected (doors, hallways, etc) within the building.

Both of these are "assembly" type uses per the IBC. The building has been designated A-2/A-3 by the architect.

Now, the IBC says a category III structure includes:
Buildings and other structures whose primary occupancy is public assembly with an occupant load greater than 300.

ASCE 7-05 goes a bit further and specifies:
Buildings and other structures where more than 300 people congregate in one area

The commentary to the IBC states:
Buildings and other structures with a primary occupancy that is public assembly with an occupant load greater than 300. Public assembly occupancies meeting this criterion will typically be classified as Group A in Chapter 3. The 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.


Would you base the occupancy category on the total occupant load of the entire structure (leading to category III for structural), or would you select one total occupancy portion of the building, e.g. the gym space that is interconnected (leading to category II for structural)?

The total occupant load of the structure is 354. Occupant load of the primary occupancy space (the gym) is 289.


My opinion is that this building should be category II. The ASCE 7-05 language of "...in one area" is what really pushes me to that answer.

Thoughts?

 

[steellion]

I think you could certainly argue for Occupancy Category II. How much would it hurt you to just go to Occupancy Category III and avoid the debate? Is this an existing building? Already designed?

 

[jittles]

Your last guess is the correct one - the building is already designed.

The building department's argument is that since it's an "A" type occupancy, they could change it to any other "A" type occupancy without triggering a structural evaluation. The new occupancy could have the interior walls taken down, and the whole building's occupant load would be combined.

It's a silly argument, IMO; there's no reasonable expectation for us to design a building for all possible future uses, but this is their current position.