How do I water proof this cement wall around the garage door:

enter image description here

Can I use something like a polyurethane crack filler or something:


Here is a closer look at the problem:

enter image description here


  • By waterproof you mean to get rid (and prevent the reappearance of) mould on its exterior [which your pictures seems to show], or do you actually get water infiltrating inside? Commented Sep 2, 2017 at 23:14
  • Well, on the outside it seems to be algea. What i want though is to prevent infiltration on the inside. Commented Sep 2, 2017 at 23:46
  • What does the inside look like (on the other side of that wall)? Commented Sep 2, 2017 at 23:49
  • It's dry. But the winter is coming (lol if you watch GOT) and I'd like to plan ahead and know what I could fill this crack with if need arises. Commented Sep 3, 2017 at 0:19

1 Answer 1


The Loctite PL seal you want to use is good for a crack depth up half an inch according to its datasheet. Since this a window-like sill, if it was properly installed, it already has some kind of PU or similar foam under it to prevent water infiltration between it and the concrete. So, if the crack looks even more superficial than that half inch, you may get away with just plastering the surface of the crack with quick-set mortar.

There's no easy way to rigorously test crack depth here because any serious test setup (e.g. dye injection & core drilling) is just as involved as a deep crack repair, which would involve first sealing the surface with the aforementioned mortar and then injecting a PU foam deeper using injection ports. I don't suggest using this method until you have an actual leak (which insofar you didn't see).

Also, ultrasonic crack depth measurement (for which you can rent equipment) is fairly difficult to apply here because the crack is very close to edge of concrete and it is going to have to deal a other unknowns like whether the cavity under the sill is filled with some foam which has lots of air bubbles in it. You might as well take the sill off and take a look.

  • Why would quick set-mordar be simpler than Polyutherine piller? Commented Sep 12, 2017 at 2:34
  • @JeniaIvanov: no, it's not simpler (you need to mix it), but it's [far] cheaper in the same quantity (which which you might not be able to get though, as it's usually sold in big bags). Commented Sep 12, 2017 at 18:32
  • I probably should simply use polyurethane then. Commented Sep 14, 2017 at 21:41

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