# V-A vs V-B



## cburgess (Oct 17, 2013)

Does a simple wood-framed wall and ceiling (studs and joists), covered with a sheet of 5/8" gyp board, qualify as a V-A construction type? It was my understanding that there's a difference between a rated assembly (such as the ones I described) and a rated protected structural member, which is what "A" is all about. For starters, it's the whole assembly that results in the hour rating, including what's on both sides of the system. The single layer of 5/8" gyp on the room side doesn't give an hour protection to the studs and joists in the wall/ceiling, does it? If this were II-A, I'd expect to see each member, including individual joists, completely enclosed in fire-resistant materials. Does a different standard apply to wood, or am I misunderstanding the whole concept?

This seems to me to be a very basic question that every person who uses the building code needs to come to grips with. And yet I've never seen a definitive explanation in the code itself.

Thoughts?

Craig Burgess


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## zigmark (Oct 17, 2013)

IBC Table 601 covers the required Fire-resistance rating requirements for the building components based on type of construction.  Chapter 7 details the allowable standards used to obtain those ratings for each component as well as the penetrations.  I'm not sure if you had a questions their or were just making a statement?

ZIG


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## cburgess (Oct 17, 2013)

No, it was a question, and I think Table 720.1 answers it. Thanks.

The problem is an existing non-sprinklered church that's renovating some restrooms, and adding 120 SF of new restroom. They say the existing and new construction are V-A, but they're basic 2x4 walls and 2x8 joists, with a single layer of drywall on each. The walls have fiberglass batts in the cavities. That doesn't appear to me to be a V-A wall per Table 720.1, and neither does a single layer of 5/8" gyp on the underside of the joists make a V-A roof/ceiling assembly. Both of those matters they can remedy easily on the new work, but verifying the existing construction is going to be harder.

The reason the existing construction is important is that if the structure is really V-B, they're already over their area limit even before the little toilet room addition and won't be able to do the work without a variance.

Craig


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## zigmark (Oct 17, 2013)

Craig-

I agree that verifying existing construction can be very difficult.  Even worse when the building has been remodeled through the years without any consideration to type of construction.  How about area increases for yards or clear space around the existing structure?  Is the building already sprinkled?  Just some thoughts.

ZIG


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## steveray (Oct 17, 2013)

Is thre drywall wrapped all the way to the exterior at windows and doors?....If not.....VB......The burden of proof is on the applicant....


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## mtlogcabin (Oct 17, 2013)

First of all Welcome to the Board

A fire rating is from the fire exposed side. Some exterior walls only require a rating from the inside.

2009 IBC

705.5 Fire-resistance ratings.

Exterior walls shall be fire-resistance rated in accordance with Tables 601 and 602 and this section. The required fire-resistance rating of exterior walls with a fire separation distance of greater than 10 feet (3048 mm) shall be rated for exposure to fire from the inside. The required fire-resistance rating of exterior walls with a fire separation distance of less than or equal to 10 feet (3048 mm) shall be rated for exposure to fire from both sides.

As for a roof/ceiling assembly there are some 1 hour GA proprietary systems the allow one layer of 5/8 installed on resilient channels


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## Builder Bob (Oct 17, 2013)

If it is type V-A , then I would assume that any ceiling registers and returns would have a radiation damper in it since they are penetrating the membrane creating the one hour roof/ceiling assembly..... If none are there, then it is type V-B.

(This is a quick rule of thumb and may get you into trouble without further research)


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## cburgess (Oct 18, 2013)

Thanks for the input, everyone. I've issued an RFI for the applicant to provide documentation of the existing construction being V-A.

And Zig, I already factored in the area increase for frontage. I don't have exact distances, but from an aerial photo it looks likely that they have at least the 30' requirement on all sides. Even giving them credit for that, though, they'll still be over the limit for V-B. That's why we need some sort of resolution on the issue.


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## globe trekker (Oct 18, 2013)

cburgess,

Another Welcome to the Building Codes Forum to you!

Instead of applying gyp. board to both sides of the framing, is it feasible / realistic for them to provide some

other type of material to achieve the "V-A" rating?  Possibly, a fire rated ceramic type of coating.  We allowed

a contractor to install a supposedly 3 hr. fire rated, ceramic based, "paint on" coating to an existing framed

wall,  to meet the different occupancy group types separation.  The Fire Chief allowed it!

Just throwing this suggestion out for other options, ..and a great question!    

.


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