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Rigid foam on poured concrete - lots of ridges and protusions


markwarren's Avatar
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Join Date: Dec 2013
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IL

12-19-13, 03:07 PM   #1  
Rigid foam on poured concrete - lots of ridges and protusions

Hi All -

I am in the planning stages for finishing my basement in northern IL. Right now, the focus is on how I will insulate the walls. Itís a lookout basement with a half wall and set of windows on one wall, and all of the other walls are below grade.

My plan is to put up 1Ē rigid foam on the concrete walls, and then frame against that with 2x4 framing. I will fill the framing with R13 batt insulation to provide extra warmth.

Two questions on the wall insulation:

Some of the walls are quite bumpy with excess concrete from when the forms were set. There are some long ridges approximately 1/4" in some spots, along with some bigger chunks. Do I need to chisel all of that off in order for the rigid foam to work? Here are a couple of examples.

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There will be two storage rooms in corners of the basement. Is it okay to leave those exterior walls not insulated, and then just use batt in the stud cavities of the walls facing the interior finished rooms?

Thanks

 
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Bud9051's Avatar
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12-19-13, 03:14 PM   #2  
The 1" rigid, then studs, then fill with Roxul would be a good solution. Fiberglass just ok. Thicker rigid if code requires.

As for those ridges, a right angle grinder with a diamond faced cup will make short work of them. A standard grinding wheel will also work, a bit slower. And yes, it is better to remove most of the ridges to fit the rigid reasonably tight to the concrete.

Bud

 
markwarren's Avatar
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12-19-13, 03:18 PM   #3  
Thanks - Is it safe to say I don't need to be concerned about taking the ridges and bumps off? They are just overfill essentially?

I'll look into the Roxul as an opttion.

 
Bud9051's Avatar
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12-19-13, 03:58 PM   #4  
As stated "And yes, it is better to remove most of the ridges to fit the rigid reasonably tight to the concrete." If leave a gap, it allows air circulation which can transfer moisture from the lower area up to the colder area at the top where it can condense and form ice. Use an adhesive in a horizontal pattern.

Bud

 
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