2 leaf/2 wall code conflict?

[cadesignr]

Hello all. Has anyone had code compliance problems with BID, as far as two wall, 2 leaf systems with an air gap, creating firestop compliance problems? After casually talking with a building inspector regarding these codes, I began wondering how you would comply, and yet maintain 2 seperated leafs? It seems one contridicts the other, and as far as the building inspector was concerned, there no getting around this one, especially in commercial building remodleing. Fireblocking must be enclosed between two leafs of one frame, if timber construction is used, which totally negates using an exterior wall as part of a 2 leaf system. In fact, this seems to imply, to comply, one would have to build 2 more walls, with one leaf each, on the interior of a room to comply with these codes, as well as meet studio isolation criteria for a 2 leaf wall. It also implys that all suggestion of building homestudio room with in a room construction of this type, actually may compromise insurance concerns. Any comments? I posted this here, as it really has to do with design at the outset rather than after the fact, and construction is NOT the issue. Compliance is.

fitZ

[John Sayers]

Fitz - as I see it you can build a triple leaf wall setup and still comply with the two leaf principle.

The two leaf system is based on two airtight wall structures. If the third - outer - wall is not airtight it plays no part as the air pressure can release. It's not hard to make the outer one non-airtight - just put some air vents into it.

I had that experience with left bank as the outer skin on the barn was 6" x 1/2" hardwood vertically with 2" x 1" battens over the joins. The hardwood was pretty green when it was originally put on maybe ten years ago and was now warped and had shrunk and there were airgaps everywhere. So I just lined the inside with 5/8" Firecheck Drywall, no insulation. I then built the studio inside that with the inside out wall construction which became the two leafs.

Worked fine.

cheers
john

[cadesignr]

Hello John, thanks for the reply. Ok, what I was really interested in, was the third leaf interferance. So it WOULD take building a 2 leaf system inside of a room to comply, as long as you have a way to vent the pressure. Cool. Hmmm, thats a whole different animal now. But, I see the reasoning behind a reversed leaf facing the interior now too. As long as you have ONE more wall system, even though it is not part of the two leaf iso assembly, it still must contribute quite a bit to the overall STC. I mean, from what I've read, this would actually lower it, but that doesn't make any sense to me, as it is still another barrier for the sound to go through. Ok John, as usual, your experience has enlightened me once again.

fitZ

[John Sayers]

fitz - the irony was that Amirel then decided he wanted to paint the exterior so the painter went and sealed up all the airgaps and painted the whole building. I didn't notice any difference in the STC of the building

cheers
JOhn