Wednesday, February 8, 2012

How Best To Build A 1hr Fire Rated Soffit?

I need a good method to build 1hr fire rated soffits. Anybody got any good ideas?

Currently the soffits look like this.

These are wrong because the wall behind and the joist bay above is not fire stopped.
I've talked to my BI and he says to use 5/8" firecode drywall on the underside of the joist bay and on the wall.

Okay, that seems easy enough, but in practice how are things like this done? I've never built one before.

I will have to build at least two soffits, probably on either side of the center load bearing wall to conceal the HVAC trunk lines. Actually, I haven't been able to decide on the best way to run the soffits...got any ideas?

HVAC Duct Diagram

Was that easy to understand? It wasn't for me first couple of times I looked at it.
This is two separate systems. One for the basement apartment and one for the main floor of the house.
How best to proceed?
It seems like I have to remove the existing soffit framing.
Then install the Sheetrock on the underside of the joists and the wall studs, but only the part where the soffit will be.
Then run my HVAC trunk line with top take-offs that penetrate the fire-stopping.
Then run what ever else I need to in the same area.
I would like to use this soffit as a chase for everything I can (no drilling through joists if I can help it). I can envision running water, gas, low-voltage lines (cable, Ethernet, phone) and romex.
As long as I correctly firestop the penetrations of the soffit is there a reason not to do this?

Simple Soffit Construction?
Then after everything is run in the soffit area I would build and attach the bottom and the one side.
I think I remember reading somewhere about a simple method to do this.
No elaborate 2by4 framing but I can't remember where I read about it.
I mean, the 'framing' of the soffit only needs to be strong enough to support the 5/8" drywall right?

Anybody got any helpful ideas?


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