Separation in an unlimited area building?

[Sifu]

Using 2018 IBC, given an unlimited area building, IIB, single story group B main occupancy, with accessory A3 and S2. Looks like they use the unlimited area provisions because the building exceeds the allowable area for A3. The combined A3 and S2 exceed 10% of the floor area. Do the accessory provisions still apply requiring that the accessory areas not separated from the main occupancy by fire barriers total less than 10%, or since it is unlimited does this still apply? They appear to be thinking it applies because they are separating the S2's, which would leave the remaining A3 at less than 10%, BUT they are only using fire partitions so I'm not quite sure. Seems like they could have gone non-separated with frontage and not worried about it, so I am a little baffled.

 

[Sifu]

And... the accessory S2's seems like they would be considered as the main occupancy per 311.1.1 but they are garages, does this make a difference?

 

[RLGA]

Assuming that Section 507.4 was the unlimited provision they were using, and the building is sprinklered with 60-foot yards, then I would say only the Group A-3 occupancy is the accessory occupancy. However, if the building is not sprinklered or it does not have 60-foot yards, there is no unlimited area provision that would suit this project if the building is over the allowable area.

Section 507.4 allows Group B and Group S occupancies to be of unlimited area (it does not have to be one or the other), so the Group B and Group S-2 occupancies are covered by the unlimited area provision. The building is of Type IIB construction, so it is not restricted by the provision's construction type limitation. That leaves the Group A-3 occupancy unaddressed.

Section 507.4 does not list Group A-3, but has specific provisions for Groups A-1 and A-2. Therefore, it leaves the Group A-3 to be permitted as an accessory occupancy per Section 507.1.1.

Section 507.1.1 states that accessory occupancies are to follow the provisions in Section 508.2. Section 508.2 allows accessory occupancies to be nonseparated. However, the area of the accessory occupancy is limited to 10% of the floor area of the story or the nonsprinklered area per Table 506.2, whichever is less.

 

[classicT]

Which provision from Section 507 are they using for an unlimited area building?

And I do not follow the OP... at first it is indicated that the main use is Group B, but then compare to allowable area for Group A-3.

single story group B main occupancy, with accessory A3 and S2. Looks like they use the unlimited area provisions because the building exceeds the allowable area for A3.

 

[steveray]

507.6 Group A-3 buildings of Type II construction. The
area of a Group A-3 building not more than one story above
grade plane, used as a place of religious worship, community
hall, dance hall, exhibition hall, gymnasium, lecture
hall, indoor swimming pool or tennis court of Type II
construction, shall not be limited provided that the following
criteria are met:
1. The building shall not have a stage other than a
platform.
2. The building shall be equipped throughout with an
automatic sprinkler system in accordance with
Section 903.3.1.1.
3. The building shall be surrounded and adjoined by
public ways or yards not less than 60 feet (18 288
mm) in width.

 

[classicT]

507.6 Group A-3 buildings of Type II construction. The
area of a Group A-3 building not more than one story above
grade plane, used as a place of religious worship, community
hall, dance hall, exhibition hall, gymnasium, lecture
hall, indoor swimming pool or tennis court of Type II
construction, shall not be limited provided that the following
criteria are met:
1. The building shall not have a stage other than a
platform.
2. The building shall be equipped throughout with an
automatic sprinkler system in accordance with
Section 903.3.1.1.
3. The building shall be surrounded and adjoined by
public ways or yards not less than 60 feet (18 288
mm) in width.

Doesn't work if the main occupancy is Group B.

 

[steveray]

Ok...so add this:

507.4 Sprinklered, one-story buildings. The area of a
Group A-4 building not more than one story above grade
plane of other than Type V construction, or the area of a
Group B, F, M or S building no more than one story above
grade plane of any construction type, shall not be limited
where the building is provided with an automatic sprinkler
system throughout in accordance with Section 903.3.1.1 and
is surrounded and adjoined by public ways or yards not less
than 60 feet (18 288 mm) in width.


If B is allowed unlimited and A3 is allowed unlimited, and S is allowed unlimited......Guess what....

 

[classicT]

Ok...so add this:

507.4 Sprinklered, one-story buildings. The area of a
Group A-4 building not more than one story above grade
plane of other than Type V construction, or the area of a
Group B, F, M or S building no more than one story above
grade plane of any construction type, shall not be limited
where the building is provided with an automatic sprinkler
system throughout in accordance with Section 903.3.1.1 and
is surrounded and adjoined by public ways or yards not less
than 60 feet (18 288 mm) in width.


If B is allowed unlimited and A3 is allowed unlimited, and S is allowed unlimited......Guess what....

You cannot mix the different methods for unlimited areas from Section 507. Pick one. That's it.

 

[steveray]

Anything in the code that actually says that? I don't see pick one....I see where you are going, just doesn't make a lot of sense...

507.1 General. The area of buildings of the occupancies and
configurations specified in Sections 507.1 through 507.13
shall not be limited. Basements not more than one story
below grade plane shall be permitted.

 

[Sifu]

They do not list any particular method for unlimited buildings, just referencing 507, so I chose 507.4 because it fits. There are several ancillary conference room areas, some fit into 303.1.2 so they follow the main occupancy. There are some storage areas so they also follow the main occupancy per 311.1.1. There is one large A3, which is not included in the unlimited occupancies per 507.4. I conclude that 507.4 directs that we follow 508.2 so the 10% limit would apply to this A3. This A3 area is under 10%, so it works as an accessory occupancy. The way I lean, the accessory storage and garages fall under 311.1.1 so it is the same as the main which equals no separation. The small conference rooms fall under 303.1.2 so they are the same occupancy as the main so no separation required. The large A3 training room does not fall under 303.1.2, nor 311.1.1 but it is under 10% of the floor so it can use 508.2 as an accessory occupancy and it is the only true accessory occupancy so there is no separation required anywhere. Sorry, it is very hard to articulate this. It is a police station and very, very cut up. The DP is making a lot of assumptions without providing a clear path and leaving it up to me to figure out. It looks like they are using a software to provide the code analysis, which is basically regurgitating code sections without really identifying a path.

I only compare the A3 for allowable area because I wonder why they go through these gyrations if every occupancy would allow it to be a straight non-separated mixed use strategy, but they are over the allowable area for an A3. They wouldn't be if they used frontage, which would certainly work. I am thinking that is just the path the software took. Then to compound things, they do separate the accessory garage spaces with what they idenify as fire partitions (but they go to deck). And, these aren't really true garages in the normal sense of the term, they are rooms with OHD used to pull in a vehicle for inmate drop-off or evidence storage or processing.

Sorry, never had the pleasure of reviewing a police station.