# Insulating basement with uneven walls



## jr1234 (Apr 13, 2019)

So, for the past couple of years I've been slowly finishing my basement, and my next step is insulating the walls. I live in a 4C climate, so pretty mild. No obvious moisture problems.

Problem is, I've just noticed that my walls are uneven. All around the perimeter of the basement, the base is about 4' of concrete block wall (height), while the remaining 3' above that is wood paneling. The concrete block protrudes about 7/8" to one inch further into the room than the paneling. 

I was planning to use 2" rigid foam to insulate the walls from floor to joists, but now I'm not sure how to address the 7/8 inch gap that would be created between the insulation board and the upper portion of the wall. Any ideas? I'd rather not use spray, so I'm looking for other options (if they're available). 

To close that gap, could I add an extra one-inch layer of foam board to the upper section of paneling? Since it's not a precise inch, that might pull me off the wall in some spots. Or could I cut a four-foot section of board to cover the concrete, then put a three-foot section over the paneling, and then seal the seams where they meet in the middle? Any other ideas? 

FYI: I do plan to hang drywall on top of the insulation. 

Thanks for your feedback.


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## chandler48 (Jun 5, 2017)

Offset your XPS to take up the 7/8", taping it completely, especially at the lateral break across the top of the ledge. You are building out a stud wall from the block wall, correct? That will even your walls up. I would not adhere any wall covering directly to the XPS. You'll need space for electrical, etc., anyway.


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## Nealtw (Jun 22, 2017)

Install 2" on the bottom and 1" inch on the top build the wall and add 1" between the studs in the top. Start with the fire stop at the top. 1/2" plywood nailed to the joist in to touch the sill plate on the foundation and out to the line of the top plate. So the top plate is nailed up to the plywood.


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## jr1234 (Apr 13, 2019)

Thanks for this feedback. 

Yes, I'm building out a stud wall from the block wall. After reading these posts, it seems like it would be okay to leave a gap (the 7/8") uninsulated, between the wood paneling upper wall and the rigid foam. Is that right? 

Thanks again.


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## user_12345a (Nov 23, 2014)

You'll need to seal any gap with some spray foam where the insulation ends (top and bottom, possibly sides) to not have a thermal bypass.

A gap can allow for convention, slightly increasing heat loss but not by a lot.


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## user_12345a (Nov 23, 2014)

> A gap can allow for convention, slightly increasing heat loss but not by a lot.


referred to gap between insulation and wall here, not at the edges.


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