Fire Separation Distance / exterior wall openings - Table 705.8

[Jay]

Hello,

Hoping someone can help shed some light on how this table is used. I have designs underway for a mixed use 12,000 sf 2 story building....F1 use (catering kitchen) and S on first floor, B use on second floor. Designs are coming along. Jury is still out on the classification being either 5A or 3B. I'm weighing the options with that.

Clients just threw me a monkey wrench by wanting to shift the new building over to connect with another existing building on the site. Buildings will touch but no proposed connection (doorway) at this time, perhaps in the future.

Here's my question, does Table 705.8 column "Fire Separation Distance" specifically pertain to the proximity of my new building to the existing building?

I can't see how that would be since any FSD of 0-3 feet doesn't permit any openings at all, which seems very unrealistic, so I must be missing something here.

Appreciate any insight. Thanks.

 

[cda]

All in same property same owner??

 

[cda]

Will both have a fire sprinkler system??

 

[RLGA]

There are three things to consider: (1) consider both buildings as one providing that the aggregate areas and overall building height complies with the height and area requirements of Chapter 5 for the most restrictive construction type; (2) consider them a completely separate buildings with an imaginary lot line between the two buildings; or, (3) connect the buildings with a shared wall acting as a fire wall.

If using 1, then there is no issue regarding the openings in the walls that face each other.

If using 2, then you have to place an imaginary line between the two buildings, and the walls and openings adjacent to the line must comply with the fire separation distances in Tables 602 and 705.8. Thus, the imaginary line must be placed so that the wall and any openings of the existing building are not in violation of the IBC, or you will need to bring them up to compliance for fire resistance and protection.

If using 3, then the shared wall must comply with the requirements for a fire wall, including structural stability. If you cannot achieve structural stability, then you can provide double-wall construction per NFPA 221. Openings can be provided in fire walls in accordance with the IBC.

 

[George McGerd]

The purpose of Table 705.8 is to regulate exterior wall openings based on fire separation distance provided between two separate, distinct buildings, which can be determined by analyzing each 'fire area' or the aggregate as required to achieve compliance with Table 506.2. With that being said, follow RLGA's advice above and that should lead you to a conclusion of whether or not a fire wall separation will be required by code.

As a designer, I always look to provide a new firewall between new construction and existing buildings (if they are touching) especially if the existing building is not part of my scope. That way you can, more-or-less, leave the existing building alone and focus your efforts on the new building you are designing.

 

[Jay]

Great assistance here, thank you all. George's clear answer on the purpose of Table 705.8 with regard to two separate buildings is what I was looking for. Though Ron does make some salient points to consider. I appreciate the three scenarios you portrayed.

All buildings are same lot, same owner.

While I would love to sprinkler the building, so far it does not seem to be required. And will save owner expense. Looking at 5B construction (sorry, I typed 3B earlier, that was a typo), the total new floor area is actually 11,000 s.f. (the other 1,000 s.f. is two story storage warehouse) my areas are as follows, total of both floors:
F1 use - 3,400 s.f.
B use - 6,000 s.f.
S2 use - 1,600 s,f,

If I add the existing building in order to analyze them as one building, per Ron's first option, that adds 1,800 s.f. of B use, still below the requirements to classify this as 5B and not need a sprinkler system. Seems like the way to go.

As you can see from the areas above, I am well below the most stringent requirements of table 506.2 and also within the height limitation, as this building is about 33 feet tall.

Thus, it would seem I am ok with looking at this entire assembly as one building, ok with the wall opening requirements not being zero since fire separation is not an issue (one building) and ok with no sprinklers. In particular, the Fire Protection Systems chapter mentions some exceptions for sprinklers in F1 under 903.2.4, for which I comply. Same for other uses in that chapter.

Hope this all makes sense. Again, appreciate the back up. Doing residential for many years.... commercial is becoming quite a lesson in code research.

Thanks
Jay