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» ICC Bulletin Board » Code Chat » Building and Residential Codes -- Non-Structural Issues » shaft enclosure

   
Author Topic: shaft enclosure
herm
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2003 IBC - 3 story apt. bldg., R-2, Type V-B const., required 1 hr. shaft enclosure (stair & elevator)is interupted on one side, by floor structure(24" open web wood floor trusses)bearing on enclosure wall. Issue - one hr. protection is continuous up to one hr. g.w.b. ceiling on underside of floor trusses and then continues again from plywood subfloor to the next g.w.b. ceiling above. What should be done at the interstial space betweeen the finished ceiling of the floor below and the subfloor above to maintain the rated shaft? Note that all framing is done prior to any g.w.b. installation, so once the floor framing is set on top of the wall it will be impossible to run the g.w.b. continuous from the bottom of the shaft to the top. Any help would be appreciated!
Posts: 2 | From: mitchell, s.d. | Registered: Sep 2009  |  IP: Logged
TJacobs
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Should not have been done like that. The wall needs to go thru the floor in one piece. You will probably need to rate the floors that are now supporting the walls. You might ask the AHJ if they will accept 1-hour spray fireproofing of the space. Good luck.

706.5 Continuity.
Fire barriers shall extend from the top of the floor/ceiling assembly below to the underside of the floor or roof slab or deck above and shall be securely attached thereto. Such fire barriers shall be continuous through concealed spaces, such as the space above a suspended ceiling. The supporting construction for fire barrier walls shall be protected to afford the required fire-resistance rating of the fire barrier supported, except for 1-hour fire-resistance-rated incidental use area separations as required by Table 508.2 in buildings of Type IIB, IIIB and VB construction. Hollow vertical spaces within a fire barrier shall be fireblocked in accordance with Section 717.2 at every floor level.

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Jake

Sometimes a great deal of effort is expended to avoid the inevitable.

Posts: 930 | From: Land of Lincoln | Registered: Apr 2003  |  IP: Logged
IJHumberson
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herm,

From your description, it sounds like the floor assembly at each level is supporting the fire barriers. If so, that does not comply. Section 707.5 requires that the supporting construction be protected to afford the required fire resistance rating of the element supported - with Type V-B construction, you have 1-hour shaft walls supported by 0-hour rated floor construction.

When shafts were constructed of block or other masnonry construction, this wasn't an issue - the shaft construction still has to be similarly separated from the rest of the building, even though it is a wood-fram-and-gypsum shaft wall instead of a masonry shaft wall.

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Ivan J. Humberson, P.E.

Posts: 109 | From: Gaithersburg, MD, USA | Registered: Mar 2005  |  IP: Logged
herm
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Thanks for the info. Actually the walls of the shaft are supporting the floors and therein lies the problem. To be able to frame up the all the walls and floors before drywalling allows no way to run the g.w.b. up both sides of the shaft at the floor trusses. If the shaft has to be continuous thru the interstitial space between the rating ceiling below and the floor above, then it seems to me that a separate bearing wall should be built out away from the shaft enclosure wall far enough so that the drywall can come in and install the drywall between the outer face of the enclosure and the wall supporting the floor structure. Would this be the most logical solution short of a masonry enclosure?
Posts: 2 | From: mitchell, s.d. | Registered: Sep 2009  |  IP: Logged
peach
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you do not have a shaft!

the designer has a problem.

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Thanks for the memories.. Frank (old blue eyes) Sinatra

Posts: 6160 | From: metro DC | Registered: Apr 2004  |  IP: Logged
Michael A.
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In my jurisdiction we would allow the wall to be constructed, the drywall applied and the floor system to be ledgered off the wall. That way the wall is not being supported by the floor and the floor would not be required to be rated. This may be a solution ( a rather tedious one) to your current situation.

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You must be the change you wish to see in the world.
—Gandhi

Posts: 28 | From: Colorado Springs | Registered: Nov 2007  |  IP: Logged
peach
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Hi Michael A..

I think you'll find ASME 17.1 doesn't allow a non rated shaft.

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Thanks for the memories.. Frank (old blue eyes) Sinatra

Posts: 6160 | From: metro DC | Registered: Apr 2004  |  IP: Logged
syarn
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herm-maybe u can install a rated shaft wall from just one side....may need to use metal CT studs.

http://www.marinoware.com/Documents/9676_MWA_Shaftwall.pdf

[ 10-08-2009, 08:30 AM: Message edited by: syarn ]

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svy

Posts: 184 | From: mt. laurel, nj | Registered: Mar 2008  |  IP: Logged
Coug Dad
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The entire floor would not need to be rated. Only enough of the floor to create a rated load path for the wall would need to be rated.

This is a continually growing problem as designers and AHJ's come to terms with the larger non rated buildings allowed by the IBC compared to the old UBC.

Posts: 237 | From: Husker Country | Registered: Oct 2008  |  IP: Logged
peach
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ASME 17.1 (the elevator code) doesn't allow it.

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Thanks for the memories.. Frank (old blue eyes) Sinatra

Posts: 6160 | From: metro DC | Registered: Apr 2004  |  IP: Logged
   

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