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Finishing basement

user-7648036 | Posted in General Questions on

I have read a number of articles on GBA re: finishing & insulating basements, but struggling to develop a clear plan. I live in Chicago suburbs (zone 5) and recently had an interior French drain installed. My plan was to install dimple mat against concrete as gap and rigid foam against mat. I would prefer to then use vertical & horizonal 1x3s against foam (before drywall) to save space vs 2×4 stud walls. But concerned about attaching 1x3s to concrete wall and creating additional holes in dimple mat. Grateful for any guidance…

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  1. Expert Member
    BILL WICHERS | | #1

    Water will tend to run down the surface of the foundation wall so some holes in the dimple mat aren’t likely to be a problem. If you’re really concerned, use the trick I use to keep water out of outdoor masonry anchors (to prevent spalling in a freeze): squirt some silicone into the hole before you install the fastener. The silicone will help to seal around the penetration and close the hole. You want to use a generous blob of silicone for this.

    If I was doing this work myself, I’d drill through the stud, foam, and dimple mat into the wall. I’d inject silicone into the hole, then I’d install a tapcon long enough to reach the recommended depth into the masonry. Note that larger size tapcons are MUCH less likely to strip out, so I’d use minimum 1/4” tapcons here.


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