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Deseloth 07-24-2013 02:02 PM

Basement foundations a wavy mess - wanted to put up 2" xps

I may be one of the select few thats read this all pages of this insualtion forum, and I like to think I've learned quite a bit, especially from Gary and Windows on Wash, so thanks!

So I had the whole plan, tear out the existing walls (a moldy, improper stud spacing and insualtion, terrible electrical, and wood and drywall touching concrete) and put up 2" xps, studs, then roxul cavity insulation.

The problem I found last night is my poured founation is an uneven mess, with vertical variations up to a 1/2". Should I still use xps? That stuff doesn't bend at all, which means there will be gaps behind it.

I'll try and get a picture up tonight to show you what I mean.

Thanks in advance for any advice. Unless that advice is spray foam, then I'll have to work weekends for the next 4 months.


gregzoll 07-24-2013 04:17 PM

Take a line stretched across the wall to find the highest poit. Then use a laser to keep the wall straight and true an inch off. After done pulling any plumbing, electrical, low voltage witing, use Spray foam to seal the space.

If you still want to use blue foam board, you would have to use shims cut from it, or glued on the back of the framing, to keep it against the wall.

Gary in WA 07-26-2013 10:57 PM

Use thinner layers of board to meet your thickness goal. Make sure it is air-tight on concrete.

No gap to insulation from foamboard for convective loops;



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