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713.12 Shaft Enclosure at Top

R

RobbyO

Member
Joined
Mar 30, 2016
Messages
11
Location
Seattle, WA
I'm having trouble understanding when 713.12 would be applicable. Per section 713.5, the shaft shall have continuity per 707.5. 707.5 states:
Fire barriers shall extend from the top of the foundation or floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto.

So if the shaft must be continuous between the floor and the structure above, when would you ever not enclose the top? Would this only apply if you stopped short of the last floor in the building?
 
713.12 Enclosure at top.
A shaft enclosure that does not extend to the underside of the roof sheathing, deck or slab of the building shall be enclosed at the top with construction of the same fire-resistance rating as the topmost floor penetrated by the shaft, but not less than the fire-resistance rating required for the shaft enclosure.

The shaft may have a higher rating than the floor/ceiling assembly and therefore it is easier and more cost effective to stop the shaft prior to the deck
 
Fair, but what allows you to not take it all the way to the deck? It seems like from the Continuity requirement, as soon as you penetrate a horizontal assembly you'd have to take the shaft enclosure up to the next floor/roof.

Say for a vertical opening connecting two stories in a two-story building, could you decide not to take the shaft enclosure to the roof deck and instead exit the shaft somewhere in the ceiling space with a fire/smoke damper and then duct to the roof opening?
 
Robby...What code do you use? What is the shaft used for? Even stair enclosures are allowed to terminate at a lid now...Wish I could post the sections, but ICC just put a stop to that...
 
I'm using 2015 IBC. In this instance I have a duct running from the roof down to two floors. I cannot use the typical exception for shaft enclosures as it's an I-2 occupancy. It seems that the requirement for Continuity would require the duct be enclosed in shaft wall construction the entire way through the second floor to the roof.

713.12 made me wonder when you would ever not take the shaft enclosure to the underside of the deck. It might open some options in my particular case since the shaft needs to offset horizontally before it can penetrate the roof deck.
 
So you can just choose at any time to end your shaft and cap it with construction with an equivalent rating to the shaft? Seems odd, since with the scenario I've described in a two-story building, the shaft could start at the second floor slab, end some arbitrary distance above that. The duct would enter and exit this little shaft box with a damper at each penetration, and then you're basically entrusting the rating of the floor to the dampers without much impact from a shaft.
 
Yep....really bugs me with stairs, but look at the 2015 for fire barrier continuity, it is pretty clear these days....I don't write, I don't like it, but I have to allow it...
 
Thanks Steveray, that at least clears my original question up. Still not sure it makes any sense that you are required to have a shaft for a two-story connection in an I-2/I-3 occupancy, but then can terminate it at whatever arbitrary distance you want above the floor. Not great Code language.
 
The building I work in has two sets of elevators, one goes to the 12 floor and the others go to the 20th floor. Not all shafts go to the top of the building...
 
Sure, but I would imagine the one that goes to the 12th floor extends to the 13th floor slab. The oddity is when you're allowed to cap the shaft at any distance above the last floor penetrated.
 
Cap it with a rated floor or rated lid...It shouldn't really matter....For example, I have an 8000 person office building in my town, 4 stories, with 8 stairs that all dump into the same unrated corridor with NONE directly to the exterior....They are adding an exit passageway to make one better. Those fire barriers would typically have to go to the deck above. Well....there is a TON of ducts, sprinklers, plumbing in that area. So now that would be "in the exit" and you would be putting a lid in it or on it anyway. (Or spending $100,000 to move it all) I imagine these are some of the reasons they are allowing more and more lids it seems...
 
The key is to completely isolate/encapsulate the shaft. Floor/ceiling assemblies generally make that easier to accomplish.
 
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