# XPS on floor sealing questions



## Windows on Wash (Aug 30, 2011)

Why 2 layers of plywood? XPS has very good compressive strength and should be fine under a plywood deck. Might as well have 1" of foam on the floor instead of 1/2"

Use foam to seal the larger gaps (closed cell) and sealant and tap to seal all the seams.


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## Gary in WA (Mar 11, 2009)

I'd go with two layers as you said, that much better at stopping room air getting to the slab; http://www.buildingscience.com/documents/reports/rr-0309-renovating-your-basment

The thicker foam board is recommended for colder climates; http://www.buildingfoundation.umn.edu/FinalReportWWW/Chapter-5/5-optimum-main.htm

where are you located? 

Gary


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## Subliminal (May 31, 2012)

I'm in NJ. It gets (relatively) cold in the winter...can get down in the teens, at any rate. And, of course, up to 100 in the summer.

I grew up in AK, so I know it doesn't get THAT cold. ;-)


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