I cannot seem to find a listed head of wall detail for a 1 hour rated fire barrier partition that terminates into a wood framed plywood deck roof. Very common condition, but I cannot find one. We can notch the gyp around the purlins and take it to the deck, or perhaps use a fire safing material to span the 5.5" gap from the underside of purlin/top track connection to the deck. Open to either option, just would like to see a listed detail. The wall is a UL 419 metal framed wall. Thanks
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Head Of Wall Detail?
- Thread starter JPohling
- Start date
steveray
SAWHORSE
Rated wood "penetrations" are something the firestopping manufacturers have been ignoring for far too long.....
Ok, Not many responses on this one. How about this solution. The current rated wall framing is stopping at the underside of the 5.5" deep purlins. The top track is secured to the purlins so there is a 5.5' gap to the wood roof deck. Rip a 24" tall section of gyp. board notched at the purlins and install so it overlaps the wall below 18+" and cantilevers the 5.5" gap vertically to meet the horizontal roof deck. 1 layer each side provides 1 hour protection
steveray
SAWHORSE
A lot of designers are drawing something similar but I would argue it is not listed....
Tim Mailloux
REGISTERED
I would look to see if Hilti has a listed fire safing joint for this type of condition
adekom
REGISTERED
It sounds like the purlins are running perpendicular to the fire barrier, and in that case I think it would be difficult to notch the gypsum membrane on each side of the fire barrier around every purlin. Each of the purlins penetrating the fire barrier would constitute a through penetration and would need to be protected with an approved penetration firestop system per 714.4.1.2. This would likely entail quite a bit of intumescent sealant on both sides of the fire barrier which I think would translate to a lot of labor and cost. I am skeptical that the gypsum board could be cantilevered as you suggest. More likely is that the wall framing would need to be continued into the purlin cavity to provide structural backup for the fire membrane.
An alternative approach would be to have the gypsum stop at the underside of the purlins and install wood 2x6 blocking in the roof cavity in between the 2x6 purlins (aligned with the gypsum above and below). IBC Section 722.1 references Chapter 16 of the AWC National Design Specification which includes provisions for calculating the fire resistance of exposed wood. Non-structural 2-by blocking has char rate of 1.5 inches per hour, which is enough to continue the 1-hour rating to the underside of the sheathing.
I would run the latter approach by your code official. My AHJ has standard ways that they interpret the code and are forthcoming about what details they will and will not accept for rated wall/floor intersections. (In some cases they allow blocking in lieu of continuing gypsum into the floor or roof assembly). Do you have GWB under the underside of the purlins as well? If you do, that will certainly help your case, and your AHJ may allow you to do one 2x6 blocking centered on the wall rather than blocking aligned with each wall face.
An alternative approach would be to have the gypsum stop at the underside of the purlins and install wood 2x6 blocking in the roof cavity in between the 2x6 purlins (aligned with the gypsum above and below). IBC Section 722.1 references Chapter 16 of the AWC National Design Specification which includes provisions for calculating the fire resistance of exposed wood. Non-structural 2-by blocking has char rate of 1.5 inches per hour, which is enough to continue the 1-hour rating to the underside of the sheathing.
I would run the latter approach by your code official. My AHJ has standard ways that they interpret the code and are forthcoming about what details they will and will not accept for rated wall/floor intersections. (In some cases they allow blocking in lieu of continuing gypsum into the floor or roof assembly). Do you have GWB under the underside of the purlins as well? If you do, that will certainly help your case, and your AHJ may allow you to do one 2x6 blocking centered on the wall rather than blocking aligned with each wall face.
This is a non rated roof/ceiling condition so no gyp on the underside or they could terminate there. Yes notching the gyp at each purlin and the lack of support framing is a problem. Yes, I think the solid blocking approach is the way to go.