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Roof/ceiling framing 1-hour rated for exterior walls with no parapet

C

CodePrincess

Member
Joined
Mar 19, 2013
Messages
7
Location
Yakima, WA
I did a search and couldn't find anything, so if there's a thread answering this, please direct me!

VB building with 5 feet of fire separation distance. Wood trusses and no parapet. Designer wants to put 1-hour on the ceiling and call it good. Is that okay? We are looking at 705.11, exception 4. Occupancy Classification is S-1.

I am not sure if that is sufficient, because Section 705.5 says that walls with less than five feet of fire separation distance must be rated from both sides. Does this include roof/ceilings as well as walls?

This is a commercial building, but I keep thinking of IRC Section R302.2.2--the exception--where a parapet is not required if there are fire-resistant materials applied to the roof decking, or the roof decking is non-combustible, and in both cases there is a minimum class C roofing. Is there a counterpart to this informaion in the IBC? The IBC commentary to Section 705.11 was no help either.

Is protecting the ceiling equivalent?? That would seem to me to be protecting from the inside, but as I asked above, does 705.5 apply to roof/ceilings?

Also, does it matter that the terminology in exception 4 is different than exception 3? Exception 3 says "roofs of...fire-resistance-rated construction," and exception 4 says "roof/ceiling framing elements...shall be of...fire-resistive-rated construction." I took out part of the sentances so you can see the parts I'm focused on.

Section 711 (horizontal assemblies) did not help. I didn't expect to find help in Chapter 15, but looked just in case, and it only covers fire classification as expected. The gypsum manual has assemblies for wood trusses, but they are all just showing ceiling protection, and nothing on the roof.

I also need to address the 1-ft overhang, but one thing at a time!!
 
Since you're referencing Section 705.5, then you must be in the 2009 IBC or later, and that states an exterior wall that is 10 feet or less is required to be tested for exposure on both sides. That means only the wall. Exception 4 to Section 705.11 gives options where a parapet is not required. The reference to roof/ceiling framing elements only refers to the joist and beams and not the ceiling ad roof sheathing. If the framing elements are parallel to the wall, only those within 4 feet of the wall are required protection. If the framing elements are perpendicular to the wall, then the entire length of all framing members on that wall require protection. In all cases, the supporting elements for the framing members require protection, so other bearing walls and columns supporting protected framing member will also require protection. The protection of these framing members does not make them horizontal assemblies.
 
Thank you! I can tell I didn't ask my question very well. Sorry!

I am in 2012 IBC.

I need to know what they have to do to protect the roof/ceiling. Bottom line: What do they have to do to their wood trusses since they don't want a parapet?

Yes, they want to use exception 4, I'm sorry I didn't make it clear that is what we are talking about.

I specified that it's an S-1 so that you'd know which to do on the parallel side.

I addressed the different wording between exception 3 and 4. You've clarified that, thank you!

Does putting drywall on the ceiling protect the trusses sufficiently to meet the exception requirements?

Or, do they have to do something to the roof--that's why I brought up the IRC.

Thank you!! I'm not clear on how to phrase questions here. I'm trying to make sure I give full info so we can focus on the target.
 
I'm going to try again. Here's what I sent a building official friend of mine. Maybe something addressed to a friend will come across more clear:

Do you know where to look for this answer? I need help with the exterior wall section in Chapter 7 of the IBC. There’s an exception to the parapet part (number 4) that says that if the roof/ceiling framing is protected then you don’t have to put a parapet on the wall. What has to be done to the framing to protect it? Do you have to put something on top of the roof like in the IRC section about townhouses, or is putting something on the ceiling sufficient?
 
The concern is the protection of property on the adjacent lot from your building from a fire event. Therefore, the protection is at the ceiling if you want to protect the trusses. Each truss can be individually protected, thereby not requiring the ceiling to be protected. At the roof, all that is required is a Class B or Class A roof covering.
 
Ok, thank you! I am going with that. It backs up the only commentary I was able to find anywhere, and that is the building codes illustrated.

I'll check your thank you box, because I super appreciate your time and help!!
 
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