Determining Fire Area size w/ mixed occupancies

[Mech]

2009 IBC

I need to determine if my building requires sprinklers in accordance with Section 903.

Section 903.2.9 states "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) . . .

3) . . .

4) . . . "



The areas and occupancies are 7,000 sf S-1 & 6,000 sf S-2.

If I treat this as nonseparated mixed occupancies, then the following applies.

508.3.1 Occupancy classification. Nonseparated occupancies shall be individually classified in accordance with :Next('./icod_ibc_2009_3_sec002.htm')'>Section 302.1. The requirements of this code shall apply to each portion of the building based on the occupancy classification of that space except that the most restrictive applicable provisions of :Next('./icod_ibc_2009_4_sec003.htm')'>Section 403 and :Next('./icod_ibc_2009_9_sec001.htm')'>Chapter 9 shall apply to the building or portion thereof in which the nonseparated occupancies are located.

If the building has no fire rated construction anywhere, how big is the S-1 fire area? Is it 13,000 sf because there is no internal fire rated assembly that keeps the S-1 fire area at 7,000 sf?

Suppose the areas and occupancies are 7,000 sf S-1 & 6,000 sf B, separated occupancies (no separation required by Table 508.4) and no fire rated construction anywhere. Is the S-1 fire area still 13,000 sf?

Thanks in advance.

 

[peach]

The S1 fire area is what it is... if over 12,000 you separate it... or sprinkle it. I'm curious what the use is for the S1 is and what the S2 is..

 

[RLGA]

If there are no fire barriers providing separation between the two occupancies, then your S-1 fire area is the total building area. Therefore, you would have an S-1 fire area that exceeds the 12,000 sf limitation and the building would require sprinklers throughout.

If a 2-hour fire barrier is installed between the S-1 and S-2 occupancies (per Table 508.4), then the S-1 fire area is 7,000 sf and no sprinkler system is required.

 

[Francis Vineyard]

Suppose the areas and occupancies are 7,000 sf S-1 & 6,000 sf B, separated occupancies (no separation required by Table 508.4) and no fire rated construction anywhere. Is the S-1 fire area still 13,000 sf?Thanks in advance.

Table 706.4. Would this separation require a 3 hr. fire wall?

 

[RLGA]

Table 706.4 is for fire walls. Based on the size of this project, a fire wall is not necessary. Fire barriers can be used for dividing a building into fire areas per Section 707.3.9.

 

[texasbo]

Is it 13,000 sf because there is no internal fire rated assembly that keeps the S-1 fire area at 7,000 sf?Suppose the areas and occupancies are 7,000 sf S-1 & 6,000 sf B, separated occupancies (no separation required by Table 508.4) and no fire rated construction anywhere. Is the S-1 fire area still 13,000 sf?

Thanks in advance.

Yes, and yes, in my opinion, even though intuitively (especially in the second case) it's a little difficult to reconcile.

 

[Francis Vineyard]

Thanks, I missed the change from 2006; the table used to be separation of single occupancies but now it includes mixed.

 

[RLGA]

Francis, you bring up a good point that I hadn't noticed in the 2009 edition. According to Table 707.3.9, for mixed occupancies the highest rating for the applicable occupancies is used. Therefore, a 3-hour wall is required. It is interesting that to be considered separated occupancies, the rating need only be 2 hours per Table 508.4 (1-hour if sprinklered), which is a change from the 2006 IBC.

 

[Mech]

Peach - Sorry to mislead you as the actual use is a car dealership with repair facilities and a parts department. I figured if I got educated on the basics, I could reason my way through the actual scenario - groups B, S-1, S-2 with a total of 27,000+ sf and 2 stories.

I do realize that repair garages are limited to smaller fire areas.