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I noticed that the caulk has failed where the bottom plate meets our concrete slab foundation along an exterior wall. I’ve removed the old caulk and vacuumed the area. The bottom plate is sitting on a foam gasket, but I’d like to fix it to help with air sealing.

This is a wood to concrete joint. I need something that will adhere to both and stay that way through temperature changes.

Should I re-caulk it with a flexible caulk or use a small bead of great stuff from my foam gun?

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  • Is this on the inside or the outside of the sill plate? And how wide is the gap?
    – SteveSh
    Commented Dec 7, 2022 at 15:25
  • Inside, just below drywall. Gaps look the be about 1/4”.
    – Josh Bush
    Commented Dec 7, 2022 at 15:34
  • "Best" is asking for opinions. Give us some objective criteria that you're looking to measure by (most waterproof, longest lasting, lowest cost, there are lots of possible "bests") and we'll be able to answer the question.
    – FreeMan
    Commented Dec 7, 2022 at 16:00
  • When building a house back in the 90's the power company had best energy practices. Their guidance was to caulk the sill plate and use expanding foam on all the wire penetrations. Maybe things have changed though.
    – RetiredATC
    Commented Dec 7, 2022 at 16:08
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    @isherwood I see a high flex sealant used pretty commonly on YouTube on high efficiency houses at the sill plate, but I think tape is more common on the exterior. Example: youtube.com/watch?v=rQj1wPyvsio Commented Dec 8, 2022 at 4:00

1 Answer 1

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I went with a small bead of spray foam. One of the “good” images from PNNL's guide (reproduced below) showed spray foam along that joint.

image of spray foamed sill plate

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