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Shaft

Sifu

SAWHORSE
Joined
Sep 3, 2011
Messages
3,317
I read many fine discussions on this forum in trying to find an answer to my question without having to ask it again, but I couldn't find one, so I'll ask.

2 story, core shell building, VB, sprinklered. Plans have an open 1st level, for future build-out. 2nd floor is the same only it does include a central corridor connecting the remote stairs and toilet rooms. The second level also includes two enclosed shafts/chases for future mechanical duct work that will connect the first story with the mechanical systems on the roof (not included in the core shell). I don't think the shafts are required to protect the floor openings for the ducts per 2018 IBC 712.1.6 & 717.6.3. So if they wanted to shoot the ducts from the 1st story to the roof, I think they could. BUT, if they are enclosed by 4 walls on the 2nd story, does that change things? The two-story opening condition per 712.1.9 that the opening not be "concealed within the construction of a wall or a floor ceiling assembly" still has me conflicted. My (literal) thinking is that the opening is concealed by the construction of a wall, but not within a wall. Obviously, a shaft is permitted in this case, but if it is a shaft, then does it not need to meet the requirements of 713? Or, does the language in 713.1 exclude this particular shaft when it says "the provisions of this section shall apply to shafts required to protect openings"? If I am correct that the shaft isn't required to protect the openings, then 713 does not apply, thereby allowing an unrated enclosure at that 2nd story (and unrated openings into that enclosure)? If that is the case then they seal the floor openings based on 717.6.3 and the walls surrounding the shaft can be unrated. Conversely, if the enclosure must meet 713, then they must enclose if by fire barriers, treat the bottom of the shaft accordingly, rate any future openings into the shaft, and rate the floors. Seems like a long way to go for a 2 story opening.
 
VB construction, so I'm assuming a non rated floor/ceiling assembly between 1st and 2nd floors? 717.6.3 (IMC 607.6.3) doesn't require a shaft in this case, just firestopping at the floor/ceiling penetrations. The duct can then be enclosed or exposed, doesn't matter. If that is not done, full shaft enclosure is required. That's the two options given. If the floor/ceiling is rated, install a fire damper at the penetration and you are good.

As far as the exception for being located within a wall, thats exactly how I read it. It has to be located within a wall, between the drywall attached to the stud framing on both sides. I have seen 2x8 or 2x10 walls used though....
 
VB construction, so I'm assuming a non rated floor/ceiling assembly between 1st and 2nd floors? 717.6.3 (IMC 607.6.3) doesn't require a shaft in this case, just firestopping at the floor/ceiling penetrations. The duct can then be enclosed or exposed, doesn't matter. If that is not done, full shaft enclosure is required. That's the two options given. If the floor/ceiling is rated, install a fire damper at the penetration and you are good.

As far as the exception for being located within a wall, thats exactly how I read it. It has to be located within a wall, between the drywall attached to the stud framing on both sides. I have seen 2x8 or 2x10 walls used though....
Correct, no rated floor assembly. My take is the same; either provide the fireblock at the floor or provide a shaft. Thanks for the input.
 
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