I'm starting to finish my basement. First step is sealing up some various places water has come in over the years. I've already fixed grading outside, but also want to seal inside.

I have one crack that I've seen water come through after heavy rains. For that I've purchased an expanding polyurethane product that goes under a layer of epoxy to force it into the crack (http://www.radonseal.com/crack-injection/diy-injection.htm).

I have several other cracks that show no evidence of water intrusion, but I'd like to seal them to be safe. I'm looking at a normal polyurethance concrete caulk (e.g. http://www.loctiteproducts.com/p/pl_seal_cms/overview/Loctite-PL-S10-Polyurethane-Concrete-Crack-&-Masonry-Sealant.htm) for these.

Obviously for the crack I've seen wet I want a good deep fill, but for the others I'd rather pay $0.20/linear foot for the Loctite than $10/linear foot for the expanding one. Will the cheaper option still provide a decent seal, or is it worth $600 to use the expanding one everywhere?

  • If you have problem of this type I don't think that any caulk would stop it. Maybe it will stop it in this particular place but water will most likely find its way. Best, but far more expensive solution would be to rebuild entire concrete slab. If this works for you I can give you the details. Commented Mar 31, 2015 at 7:36

1 Answer 1


You are really brave to finish a basement with a known moisture issue. I for one wouldn't spend a penny on finishing my basement until I have seen it go through a wet season without failing. Not telling you to stop but would warn to slow down. Get your framing/electric/plumbing/whatever done and let it go through at least 4-5 months before finishing touches.

As for cracks, if it has leaked before then I would suggest that you always go with an epoxy. There are too many on the market for me to give a recommendation. I have used at least 10 and was happy with 8 of them. Concrete caulk is not your answer to seal a leaking crack but can be used on the outside of the house to keep issues at bay. Also make sure you read the instruction on the epoxy. You are probably going to have to chisel out the crack to make it larger so the epoxy can fill it.

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