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Basement wall against foundation

Patrick Cook | Posted in Green Products and Materials on

I am about to start working on finishing out our basement, and have been a little surprised that the most confusing part has been what materials to use when framing in front of the foundation.  I spoke with our local inspector and it sounds like the code allows for a few options.  I am mostly curious about what the “best” option for our area is.  I obviously want good longterm results while avoiding overkill.  I am in Canton, GA (Climate Zone 3):  

Option 1 (and this sounds like what most contractors do): Frame the wall just off of the concrete and insulate between the studs with R20 Mineral Wool.  3/4″ plywood against the joists for vertical fireblocking, and an extra pressure treated piece of lumber against the concrete every 10′ for horizontal fireblocking.

Option 2 (what I think I want to do and what I see on YouTube most frequently, but may be overkill for my area): Glue 1″ XPS directly to the Concrete, frame the wall against the foam, use R15 Mineral Wool between the studs. Then same 3/4″ plywood fireblocking against the joists and spray foam where the studs separate from the XPS.

From what I have read, I don’t think I need a vapor barrier, though the XPS acts as one.  Let me know what best practice for my area is.  A lot of the stuff I see seems to be focused up north where the temperatures are a lot more extreme.  The house was built in 2016 btw.

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