# Fire Area vs separated occupancy



## ThatOneGuy (Apr 13, 2021)

Hello all,

IBC 2015.  Designing an office building with an attached warehouse. Office building is roughly 11,000 SF, warehouse is roughly 3,000.  Trying to determine separation requirements and avoid needing fire sprinklers. 

*Interpretation 1:* No fire-rating required between warehouse and office.
Justification: Table 508.4 says NR for a B-to-S1 separated occupancy. 903.2.9 says sprinklers only required where S-1 area is >12,000.  Three is less than twelve, good to go.

*Interpretation 2:* A 3-hour wall is required between warehouse and office.
Justification: 903.2.9 uses the defined term _FIRE AREA_ when listing the 12,000 SF limit. Chapter 2 defines _fire area_ as bounded by exterior walls or rated construction (paraphrasing for brevity). Then follow to Table 707.3.10 for ratings required "between fire areas". S-1 requires 3 hours, and the paragraph above clarifies that in mixed occupancy the highest rating applies. Without this 3-hr wall the fire area is 14,000 and sprinklers would be required.

Interpretation 2 seems the more technically correct to me, but it also seems to be missing the point. The warehouse is only 3,000 SF but still has to count the entire building footprint of 14k in the fire area? Unless the building is split into two parts by (probably) a big block wall. 

Looking forward to your opinions on the interpretations here.


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## cda (Apr 13, 2021)

I think I am going with number one

plus no sprinklers


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## RLGA (Apr 13, 2021)

Fire areas and occupancy separations are two different things.

Both of your interpretations are correct. The occupancy separation requirements are based on comparable fire loads. Group S-1 and Group B are determined to have comparable fire loads. The concept of occupancy separation is to separate occupancy groups with a lower fire load from those with higher fire loads.

Fire areas provide compartmentation to limit the spread of fire. Storage areas are generally large open areas with little construction that restricts the spread of fire. Depending on the type of office building, many have several small offices and other partitioned spaces (closets, conference rooms, restrooms, breakrooms, etc.) that provide some level of compartmentation, even though the construction may not be fire-resistance rated.

The real question to ask: If Group B and Group S-1 have comparable fire loads, why does Group S-1 have a maximum fire area threshold while Group B does not?

If you look at the statistics (NFPA fire data for 2014 to 2018), the number of fires within storage buildings compared to office buildings is similar (storage=22,401 to offices=18,972). The property loss, death, and injury numbers are also similar between the two types. However, this is based on the fact that storage spaces have had fire area restrictions for years. If there were no fire area requirements for Group S-1, the data numbers for storage would likely be higher.


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## Rick18071 (Apr 14, 2021)

What ever is strictest


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## ThatOneGuy (Apr 14, 2021)

RLGA said:


> Fire areas provide compartmentation to limit the spread of fire. Storage areas are generally large open areas with little construction that restricts the spread of fire. Depending on the type of office building, many have several small offices and other partitioned spaces (closets, conference rooms, restrooms, breakrooms, etc.) that provide some level of compartmentation, even though the construction may not be fire-resistance rated.
> 
> The real question to ask: If Group B and Group S-1 have comparable fire loads, why does Group S-1 have a maximum fire area threshold while Group B does not?


Very interesting. I wasn't thinking about compartmentation due to non-rated construction factoring in to the code logic. However, I think the original question about what separation would be required remains open. 
If the purpose of a fire area threshold in S-1 is to keep fires from spreading uncontrolled through large open areas, why would that be applicable in this situation where the "large open area" is actually only 1/4 of the defined maximum? It's the adding in of the adjacent office space (compartmented as you described) that seems off to me.


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## cda (Apr 14, 2021)

From the author:::




			https://www.specsandcodes.com/articles/code_corner/The%20Code%20Corner%20No.%2027%20-%20Fire%20Areas.pdf


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## RLGA (Apr 14, 2021)

ThatOneGuy said:


> Very interesting. I wasn't thinking about compartmentation due to non-rated construction factoring in to the code logic. However, I think the original question about what separation would be required remains open.
> If the purpose of a fire area threshold in S-1 is to keep fires from spreading uncontrolled through large open areas, why would that be applicable in this situation where the "large open area" is actually only 1/4 of the defined maximum? It's the adding in of the adjacent office space (compartmented as you described) that seems off to me.


Fires can start anywhere, and many people assume fires will start in the storage area and spread into the occupied office areas. However, a fire can just as easily start in the office area and spread into the storage area. If the storage area is not compartmentalized, once the fire reaches it, it will spread more rapidly than it did through the office area. The fire area separation does not need to be right at the demarcation between office and storage--it can be anywhere provided the resulting fire areas are under the threshold to avoid having sprinklers.

If the building consisted of a 13,000 sf storage area and a 1,000 sf office area, you would have to either provide a sprinkler system or divide the storage area to create two fire areas under the 12,000 sf threshold. 

If you have an office building at 13,500 sf and a small storage room at 500 sf, then Section 311.1.1 (2018 IBC) allows you to have accessory* storage spaces without classifying them as Group S-1, which would otherwise trigger the fire area threshold. However, even though the building in the OP's case has a smaller storage area compared to the office area, it probably would not be considered accessory storage.

* We already had a discussion on the forum about the use of the word "accessory" in Section 311.1.1 compared to its use in Section 508.2.


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## Tim Mailloux (Apr 14, 2021)

or you just do the smart thing and put sprinklers in the building


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## ThatOneGuy (Apr 14, 2021)

Tim Mailloux said:


> or you just do the smart thing and put sprinklers in the building


Believe me, I'd like to. It's an issue with this particular client. Honestly the question about this separation wall is peanuts compared to the complications of rated corridors on the office side which would all go away if they'd just agree to sprinkler the building.


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## Paul Sweet (Apr 14, 2021)

Tell your client to ask their insurance agent how sprinklers would affect their insurance rates.


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## cda (Apr 14, 2021)

And Uncle Congress is giving money away!!!







						Fire Sprinkler Tax Incentives | W&M Fire Protection
					

Learn more about the tax incentives for installing fire sprinkler systems in your building. Call W&M Fire Protection today.




					www.wmfireprotection.com


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