Firestop perimeter


Old 01-09-09, 03:10 PM
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Firestop perimeter

Remodeling my basement and my building inspector stated that there needs to be "firestop perimeter walls against foundation at top plate".

Can anyone provide a little advice on this? Is it as simple as installing another 2x4 (this time treated) next to the top plate and touching the foundation?

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Old 01-10-09, 11:01 AM
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I've never heard of an inspector asking for this, I don't see why he would. You really should ask him exactly what he wants to see so you only have to do this once. One thing I learned a long time ago, the building inspector is always right.
Old 01-10-09, 12:23 PM
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I'm guessing you have interior framed walls in your basement that are spaced maybe 1" away from your foundation walls? And that the inspector doesn't like to see the 1" gap behind the top plate of the wall.

Craig is right about asking what they want to see, and how they want it done. There's no sense arguing with them, just communicate and find out what exactly they want.

Last job we did that was like that, they were happy with taking a can of fire-rated spray foam and filling that gap, just to stop the airflow there. Sometimes it makes more sense to tack up some 14 1/2" pieces of plywood wherever you can, to reduce the amount of foam you need to use. Any wire or plumbing penetrations through the top plates had to be sealed with foam in a similar way.
Old 01-10-09, 04:48 PM
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I had a job where I was asked to firestop and it was a different kind of insulation material. Hears a site with the basic same material
Safing Insulation

Safing Insulation
I'm in the construction and new things are good but it gets out of control and at a big burden of cost to the job and customer its a wonder we made it this far
Old 01-20-09, 01:14 PM
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Again, I hope it's not too late....

One easy way is to ask what material can be used. In my county, regular old fiber glass is OK. If you can use that AND your walls ARE 1" or so away (which is the only reason I can think of that they would want the firestop) you can do the following:

Cut a long piece of fiberglass, the smallest R rating you can find. Then cut it into strips about 4-6" wide. Then just work the strip in behind the framing at the top of the wall. It doesn't have to actually go behind the top plate, it just has to be high enough to stop any fire from getting past the top plate and into the upper floor joists. I would work it as close to the top plate as I can, and then maybe tuck a half inch or so behind the top plate.

I made the mistake of using rockwool. It is very brittle comapared to fiberglass and little fibers just come flying off of it. I had to cut 15" lengths to be able to work it behind the framing. Next time, I would use regular fiberglass.

Also, don't forget, if you drilled any holes in your top plate for wiring, you'll need to caulk them with a fire rated caulk.

Good luck,
Old 01-20-09, 03:24 PM
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Thank you all for the comments. Direction from the BI is to use drywall and attach it from the joists (or blocking) back to the foundation or rim joist. Using fireproof caulk around the conduit.

So...I picked up some 5/8 drywall and will slice it up.

Thanks again.

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