1 hr fire rated storage room

[michaelj]

have a 1 hr rated storage room, designer has submitted a UL-U419 wall, typical 1 layer (each side) 5/8" type "X" Gypsum, no problem. For the ceiling he submitted a UL-P516 2 layers 5/8" bottom side of framing, not a problem. My question is is there a detail on how the two should join? walls extend all the way to the bottom of roof deck (typical metal building) and the ceiling is down about 5'. The two layers on the ceiling will join just one layer on the wall. They say there is not a detail. I have not found any reference to how this joint should be. Any thoughts?

 

[Builder Bob]

why is the ceiling being rated? if the walls go to the roof deck

 

[cda]

Kind of like a rated corridor does???

 

[JPohling]

yeah I dont think that would need a rated ceiling if the walls are to the deck.

 

[steveray]

There is ALWAYS a detail....they are just too lazy to find it....I agree with the esteemed members above...if the drywall (entire rated wall assembly)goes to the deck...ceiling not required...other wise the ceiling needs to be the lid on the walls, not side hung....Hence the reason fire rated platform type framing is so difficult to do correctly....

 

[Builder Bob]

If I was the designer, I would extend the walls to the roof deck and install ACT in the storage room if the ceiling aesthetics are that important. otherwise, i would omit the ceiling and save a few bucks

 

[michaelj]

The problem with the roof deck and wall connection is the roof is a typical metal building with "Z" purlins but then have a mesh liner attached to the bottom of the purlins with 8" batt insulation running between purlins and another 4" batt laying across the purlins under the metal decking. the standard detail from the MBMA for a fire rated wall and deck is to compress the standard 2-3 inch roof insulation, but since this has the liner mesh and extra insulation it does not meet that detail.

 

[JPohling]

So, your saying you cannot figure out a decent detail at the wall to deck connection? then terminate the walls below the deck and use a rated tunnel type detail for the lid. build the lid just like the wall and your done. I would want to see a slip track if the walls are connected to the roof deck.