I have a garage made from cast concrete panels. The gaps between the panels and at the bottom have clearly had an attempt at waterproofing in the past but it has failed, so now I get standing water when it rains.

What would you recommend to seal the gaps between and below the panels?

enter image description here

enter image description here

Probably won't get the garage perfectly sealed since the door is at the bottom of a slope and there's no drain, but hopefully I can improve it a bit.

  • Have you tried the expandable foam? Apply it with one side taped or boarded.
    – r13
    Commented May 1, 2021 at 11:14
  • Hmm hadn't thought of that though I kind of detest expandable foam - think I'll try silicone instead as Jasen suggested.
    – Timmmm
    Commented May 1, 2021 at 12:23
  • That's a good idea. You can insert rigid foam instead of the backing rod to minimize the quantity of silicone sealer (apply it on both sides to prevent water and moisture)
    – r13
    Commented May 1, 2021 at 13:06
  • 1
    For the floor gap, grading away from the outside of the building (and, evidently, adding a trench drain at the door) would help to keep water away from the joint in the first place.
    – Ecnerwal
    Commented May 1, 2021 at 14:10
  • Yeah unfortunately one wall is built about an inch from a retaining wall so it's a bit impossible. A drain would definitely help.
    – Timmmm
    Commented May 2, 2021 at 14:35

1 Answer 1


clean with high-pressure water jet, allow to dry, Seal with a neurtral-cure silicone after fitting a backer-rod to keep the silicone depth within the acceptable range (consult the silicone packaging).

  • Ah thanks! Any idea about the floor or would you just do the same thing there? Looks like they used some kind of mortar previously.
    – Timmmm
    Commented May 1, 2021 at 12:26
  • 1
    I'd do the same thing, possibly making a slight groove using a diamond blade in an angle grinder so that the caulk can get in there and be protected from abrasion.
    – Jasen
    Commented May 1, 2021 at 12:45
  • Ah good idea, I will give it a go, thanks!
    – Timmmm
    Commented May 1, 2021 at 13:23
  • This is fine advice, but @ecnerwal had it right in the comments: deal with the exterior first. Commented May 1, 2021 at 14:30
  • (and for the vertical crack, I'd work from the outside...) Commented May 1, 2021 at 14:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.