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S2 - B Use - Firewall 9000 Sq Ft

J

jeffo

Registered User
Joined
Nov 12, 2021
Messages
24
Location
Texas
Hi,

I recently was looking to expand my building. Currently it is a metal building of 9000 sq ft, with about 1500 sq ft of office built out (all 1 story). It was built in the 1970's. We have been here for 15 years.

My plan was to build it out to 11900 sq ft.

Upon inspection from the city, they stated a 1 hour firewall was needed to be installed between the office and the storage area.

I had checked with the city before as I was looking to build a new warehouse and was told I would not need to have a sprinkle system in place unless above 12000 sq ft.

When I researched it in the past I was told I did not need the firewall due to the following:
Non separation is not required until the less of the height and area from table 503 is exceeded for occupancy. F2 is 12000 and B is 19000.

I just really want clarity on this as I seem to be getting no response from the building inspector as I think they are just overloaded in work. Do I need a firewall per code, or do I not?

thanks!
 
You most definitely do not need a firewall. Allowable area (assuming Type V-B construction) for B is 9,000sf. For F-2 it as 13,000sf. (UPDATE TO S-2 => 13,500sf)

With the total area being greater that the allowable area for a B-occ., you will not be able to go mixed-use non-separated, as you would follow the most restrictive (B) requirements.

The feasible alternative is to go mixed-use separated and follow IBC Table 508.4. Per this table, the required separation is a 2-hr fire barrier. Note that per IBC Section 508.4.4.1, the construction of the required separations is to follow Section 707 for fire barriers. There is a huge difference in a fire barrier and a fire wall, mainly the requirement for structural independence for fire walls.

Here is the math to substantiate IBC Section 508.4.2:
(1500/9000)+(10400/13000)=.96
(UPDATE TO S-2 => (1500/9000)+(10400/13500)=.94 or 94% of allowable building area)

Meaning, you are 96% of the allowable building area with the proposed addition.
 
Last edited:
Note for my above post, I followed the 2015 IBC for Texas. Assumed Type V-B construction. And used the areas provided in the OP, which may have been rough numbers.
 
Is the interior office construction wood frame or metal stud? Also, the thread title states "S2," but your post states "F2." Which one is it?
 
I am in TX, using 2015 ICC now.

S2 (sorry typo on the F2)

I believe Wood frame on the interior, non load bearing.

It is a 9000 sq ft metal warehouse, eaves height is only like 14 or 16'.
 
A fire wall would be required since the existing building is 9,000 sq. ft. and the allowable area for a Group B occupancy (most restrictive) is 9,000 sq. ft.

To avoid having a fire wall dividing the Group S-2 area (between new and old), the separation between the Group B and S-2 occupancies would need to be a 2-hour fire barrier. This would require demolition of existing construction to accomplish.
 
There's no need for a firewall based on the provided information.

You would need a 2hr fire barrier to separate occupancies between B and S-2. That doesn't necessarily mean demo. It depends how the wall is built now. It may be possible to add extra gyp to the existing wall and maybe extend the wall to the bottom of the roof deck.
 
FYI for all, I updated by preceding posts with bold red font to reflect the OP's clarification regarding F-2 vs S-2 use.
 
Magnesium - nope. These are AL356. Mg wheels are super high end. Strong but brittle -- and light. Most spun cast wheels are closing in on the weight savings once seen in Mg.

Sounds like I need my engineer to get the 2hr barrier drawn up asap.

Also, on the report it was noted:
There are also issues with zero or near
zero lot lines and multiple buildings on the same lot.

These buildings were built and approved more than 40 years ago. I have a recent survey I just did so I am really not sure what the building inspector is wanting me to do here.
 
You should hire an architect. Engineers typically do not know the building code outside of structural requirements.

As for the zero lot lines, if you're not changing those walls or the occupancy they enclose, they shouldn't need to be brought to current code. But there may be local requirements based on extent of new work.
 
jeffo said:
Magnesium - nope. These are AL356. Mg wheels are super high end. Strong but brittle -- and light. Most spun cast wheels are closing in on the weight savings once seen in Mg.

Sounds like I need my engineer to get the 2hr barrier drawn up asap.

Also, on the report it was noted:
There are also issues with zero or near
zero lot lines and multiple buildings on the same lot.

These buildings were built and approved more than 40 years ago. I have a recent survey I just did so I am really not sure what the building inspector is wanting me to do here.
Click to expand...
Where you have multiple buildings on a site, you may either treat them all as one building, or they must be separated by an imaginary lot line. Assuming Type V-B construction again, but if the buildings are less than 20-ft apart, some of the exterior walls would need to be rated construction where using the imaginary lot line method. This comes out of IBC Table 602 and IBC Section 503.1.2.

503.1.2 Buildings on Same Lot
Two or more buildings on the same lot shall be regulated as separate buildings or shall be considered as portions of one building where the building height, number of stories of each building and the aggregate building area of the buildings are within the limitations specified in Sections 504 and 506. The provisions of this code applicable to the aggregate building shall be applicable to each building.
 
If these "wheels" are predominately combustible, then it is a Group S-1, which would actually help your situation.
redeyedfly said:
There's no need for a firewall based on the provided information.

You would need a 2hr fire barrier to separate occupancies between B and S-2. That doesn't necessarily mean demo. It depends how the wall is built now. It may be possible to add extra gyp to the existing wall and maybe extend the wall to the bottom of the roof deck.
Click to expand...
However, any openings would need to be replaced with 1-1/2-hour-rated openings. Usually, these office buildouts within pre-engineered metal buildings do not have the walls go all the way to the roof deck. If that is the case, then either the walls need to be extended to the deck or a new 2-hour horizontal assembly needs to be provided.
 
Yes, the office is framed out inside, thus it does not go all the way to the ceiling. The wheels of course are not combustible -- just wheels. I also have an area where we work out and roll stuff in and out that has a wall unit on it, and it has the hanging meat locker like plastic strips. Does this also have to have the 2 hour barrier? It is kind of crazy as I really do not see the purpose of the barrier. Everyone can walk from their office to the front door in under 5-10 seconds!!
 
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