12,600 sf 1 story building questions: Automatic sprinkler system required? Rated Wall?

[palikona]

I'm designing a 12,600 sf 1 story commercial building. Half will be "B" (offices) and half will be "S1" (Mod. Hazard storage). The way I'm reading the IBC, the building would only need a sprinkler system if the S1 use was over 12,000 sf total. But given that the S1 area is half that, I believe that it doesn't need a sprinkler system. Is this correct?

Also, given the different use groups, do I need to provide a 1 or 2 hour rated wall between "B" and "S1"? I'm thinking yes?

Thanks for the help.

 

[ICE]

2020 California Building Code:

903.2.9 Group S-1. An automatic sprinkler system shall be provided throughout all buildings containing a Group S-1 occupancy where one of the following conditions exists:
1. A Group S-1 fire area exceeds 12,000 square feet.
2. A Group S-1 fire area is located more than three stories above grade plane.
3. The combined area of all Group S-1 fire areas on all floors, including any mezzanines, exceeds 24,000 square feet.
4. A Group S-1 fire area used for the storage of commercial motor vehicles where the fire area exceeds 5,000 square feet.
5. A Group S-1 occupancy used for the storage of upholstered furniture or mattresses exceeds 2,500 square feet.

No separation is required between a B and S1 occupancy.

 

[palikona]

Sorry, I should have said this is in Colorado and is under the 2021 IBC.
I'll have to check about 4. and see if they are storing commercial motor vehicles.

Thank you,
Chris

 

[palikona]

The client will not be storing motor vehicles in the group S-1 area. Sounds like we do not need a sprinkler system because half the building is S-1 and half is B, correct? Thank you.

 

[Yankee Chronicler]

If the two occupancies are not separated, the building area is limited by the occupancy that has the stricter requirements. Both B and S-1 are limited to 9,000 s.f. in construction type V-B, so your construction type will have to be V-A or II-B unless you can get a huge increase for excess open perimeter.

 

[Yankee Chronicler]

The client will not be storing motor vehicles in the group S-1 area. Sounds like we do not need a sprinkler system because half the building is S-1 and half is B, correct? Thank you.

Unfortunately, no. IBC definition of "Fire Area":

[BF] FIRE AREA. The aggregate floor area enclosed and
bounded by fire walls, fire barriers, exterior walls or horizontal
assemblies of a building. Areas of the building not provided
with surrounding walls shall be included in the fire area if such
areas are included within the horizontal projection of the roof
or floor next above.

So, although other parts of the code don't require a fire separation between B and S-1, if you want to consider the S-1 as a separate fire area, you do have to provide a fire wall or a fire barrier between the two occupancies.

 

[palikona]

If the two occupancies are not separated, the building area is limited by the occupancy that has the stricter requirements. Both B and S-1 are limited to 9,000 s.f. in construction type V-B, so your construction type will have to be V-A or II-B unless you can get a huge increase for excess open perimeter.

It’s going to be a prefab metal building so I should be ok, right?

 

[palikona]

Unfortunately, no. IBC definition of "Fire Area":



So, although other parts of the code don't require a fire separation between B and S-1, if you want to consider the S-1 as a separate fire area, you do have to provide a fire wall or a fire barrier between the two occupancies.

Ah right. Ok, I’ll be providing a 1 hour wall.

 

[walker.t]

I’ll be providing a 1 hour wall.

Where do you get a 1-hour rating? Wouldn’t you need a 3-hour separation for the S-1 occupancy per Table 707.3.10?

 

[Yankee Chronicler]

Where do you get a 1-hour rating? Wouldn’t you need a 3-hour separation for the S-1 occupancy per Table 707.3.10?

Correct. B to S-2 would be 2 hours, but S-1 requires 3 hours (except to H-1 or H-2).

 

[walker.t]

so your construction type will have to be V-A or II-B

Table 506.2 NS allowable areas for Group B and Group S-1 in Type III-B are 19,000 s.f. and 17,500 s.f. respectively, so if the building is 12,600 s.f. Type III-B would allow nonseparated mixed occupancy.

But they still need to deal with the 12,000 s.f. S-1 fire area limit from 903.2.9. They need to do a cost-benefit analysis and determine if that 600 s.f. is worth sprinkling the building or the cost of building an appropriate wall to create two fire areas.

It’s going to be a prefab metal building so I should be ok, right?

You have to take into consideration the materials used to frame interior walls, if you wanted to use wood framing that would eliminate Type II construction but it could be Type III.