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tomdor 12-31-2012 04:01 PM

Rigid Foam Under Rat Slab
Okay, so I've searched the web and searched through this forum and can't find the answer to one question I have.

I will be pouring a rat slab into my crawl space to prevent the persistent buggers from tunneling under my footing. I also plan to make this a conditioned crawl.

Should I pour the rat slab over rigid foam? Would it make a difference? I'm in climate zone 4c (Seattle)?


Windows on Wash 12-31-2012 05:23 PM

Why kind of rigid foam?

I can't hurt.

Gary in WA 12-31-2012 10:38 PM

PS. install 6mill poly under the whole slab first...

tomdor 01-01-2013 12:25 PM

Happy New Year and thanks for the great info in the links!

I was planning on using XPS but do you know if I can use R-Matte Plus ISO?


Windows on Wash 01-02-2013 09:44 AM

Use XPS under the slabs.

ISOs are moisture sensitive.

Gary in WA 01-02-2013 10:31 PM

The foil-facing is good IF there is a space, but not with a slab over it.... Just don't puncture the foil with rocks or pea gravel (in the concrete mix), hmm.....;

Or it can/will absorb 7 times more water in the test as XPS;


tomdor 01-03-2013 02:02 PM

hmm experience with the foil is that if often gets a small puncture if you look at it the wrong way.

Thanks for the add'l info:)

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