1 Hour Rated Horizontal assembly

[Red Stick]

I have a 4'x6' janitor's closet that needs a 1 hour rated ceiling to separate it from the area above (bar joist and roof deck). It currently has a 2"x4" framed ceiling with 5/8" gyp. bd. top and bottom with fire tape. I can find UL and GA files numbers for 5/8" on a wood truss bottom chord, which list it as 1 hour rated for the bottom chord. However, I can't find anything for a small horizontal assembly, protected from both sides.

Any suggestions?

Thanks

Jeremy

 

[Francis Vineyard]

Ask the manufacturer of the wood truss.

 

[texasbo]

Don't think you're going to find one with 2x4 joists, although I am a little confused by assembly 21 in Table 720.1(3), 2006 IBC. That assembly doesn't specify joist depth, but it's a lot of work. My question is: are you sure you need a 1 hour ceiling for the closet?

 

[Red Stick]

The building inspector wants a 1 hour separation, typically to the roof deck above. There are bar hoist, etc above which makes this difficult. He said that as long as a ceiling is protected from above and below, he us satisfied. The fire marshal wants a UL number. Everything I have seen is for floor/ceiling rather than a horizontal separation.

 

[texasbo]

A one hour floor/ceiling is a horizontal separation. If it is supported by one hour walls, then it complies. I still can't imagine why a 4x6 janitor closet would need separation.

 

[Francis Vineyard]

Jeremy, I'm still a little confusedof the situation, but it sounds like because of the existing roof trusses you need to assemble this from one side; not being able to access from above; if that's the case; search for horizontal (corridor) shaft wall or elevator shaft wall assemblies.

Hope this helps.

 

[texasbo]

Francis; I think the problem is that the trusses make it difficult to carry one-hour wall assemblies to the underside of the roof deck.

The real problem is that some asshat is making him rate a 24 square foot closet.

 

[Francis Vineyard]

texasbo; it doesn't make sense to me either; I thought Jeremy was saying he needed a UL assembly for the FM because the existing one didn't comply.

"The real problem is that some asshat is making him rate a 24 square foot closet" very true; there the ones that gives us a bad name.

 

[fatboy]

yup........small man, big stick.........ahole.

 

[RLM-Architect]

The GA-600 Fire Resistance Design Manual in assembly numbers FC 5406 (2x10 joists-24" o.c. including trusses), FC 5407 (wood I-joists-24" o.c.) and FC 5408 (parallel chord wood trusses-24" o.c.) that indicates the use of a double layer of 5/8" Type X gyp board on the bottom of joists to be qualified as a 1 hour rated membrane.

The requirement for the janitor closet protection is an issue of both the NFPA 101 and the IBC. Either 1 hour separation OR sprinkler protection will satisfy the Code.

A single sprinkler head from the domestic water supply will also be permitted if the entire building is not sprinklered.

 

[Examiner]

There is the shaft wall system that can be used in the horizontal plane. I have used it many times. Why not ask the inspector to quote chapter and verse where he is citing the violation. It would be interesting to see that one. If anything the storage closet and any others in the job as an aggregate total would most likely be under the 10% rule for mixed occupancy separation and therefore would not need separation.