enter image description here I planned to use Loctite Polyseamseal with a backer rod. I called Loctite tech support and they advised against it in that Polyseamseal won't hold up in a standing water situation. That surprised the heck out of me! The advertising and spec sheet did not mention that prohibition. Anyhow,it's an awfully big joint to caulk. Would appreciate DIY any suggestions.

*UPDATE: I have attached A PHOTO OF THE STALL. The floor is ceramic tile and the two walls are some sort of composite panels with gold marble patterns.

I would appreciate any help or guidance.

  • 1
    I wouldn't be caulking a gap that big. Mar 12, 2015 at 1:42
  • Chaulk can be used for small holes...this is way to big,plus you have a water involeved,and temperature variations.Give us a picture if possible and maybe bit more detailed description of the problem so we could help Mar 12, 2015 at 13:44
  • Thanks for your help. I will take photos and post them and give further information . But first I have to get my camera and lights and setup to get good quality photos as best as I can.
    – C.Thomas
    Mar 12, 2015 at 21:57
  • Rather than caulk, I'd browse the tile section for some kind of piece you can use as trim at the base of the wall to cover over the gap. Typically you'd install the tile floor first, and the walls would overlap the floor with at most a 1/4" gap.
    – BMitch
    Mar 13, 2015 at 1:36
  • If he did that, should he lay down some caulk underneath the new tile as a sealant? I'm just wondering what's at the bottom of that crack...and what isn't.
    – aaron
    Mar 13, 2015 at 1:51

1 Answer 1


I'd grout it. Then when the grout fails I'd do it again. The third or more time gets caulk as a last resort before gutting it.

Before the picture was up I had envisioned where the floor meets a tub; grout always fails there after a few years, but by then it's all pretty well settled and a touch-up grouting usually lasts much longer.

However what you have there... erm, what do you have there? Any idea if that was a kit or home made? Is there a watertight, factory manufactured basin down there or what? I'm going to assume there is and someone added walls and a floor for aesthetics. Otherwise, gut it! So, it kinda doesn't matter what you use, until it starts growing mold. This is where the breathability of grout wins, over the moisture trapping capabilities of caulk.

If you MUST use caulk, use silicone. Latex caulk gets grubby much faster and is otherwise unsuitable in a wet location; insure that your silicone is suitable. I personally don't agree with the answers there about always using caulk at changes of plain; I try to get away with grout for as long as possible, everywhere. You can always come back and hack-job some caulk at it. When the time comes to readdress it, I'd rather be dealing with lose chunks of grout than removing old, moldy caulk mess. And if you use caulk, you will be readdressing it at some point, instead of the maybe you'd get with grout.

  • I don't know if its a kit, looks homemade but I dug out two layers of plastic backer rod which was covered with what appears to be semi- brittle epoxy about 1/4" thick(I had to chisel out) and the backer was moist.
    – C.Thomas
    Mar 13, 2015 at 14:03
  • I don't know if it's a kit or homemade. I had to chisel out what looks like semi-brittle epoxy about 1/4" thick and underneath was two strips of plastic backer rod this which was moist to the touch. I noticed no mold! If I fill it entirely with grout,that's breathable won't water and moister seep down though the grouted gap?
    – C.Thomas
    Mar 13, 2015 at 14:18
  • @C.Thomas Epoxy is definitely another option (consider replacing 'caulk' in your title with 'solution'). It becomes obvious once grout has cracked, with caulk it's hard to tell it's failed until you see mold. Akin to the 24 hour band-aid rule, you don't want something absolutely impermeable always trapping water. IME, A bead of caulk that has come lose, soon turns into a mold party because it never gets a chance to dry out underneath there. It's not that grout is all that porous (once sealed), it's that caulk isn't at all and it creates a 'situation'.
    – Mazura
    Mar 13, 2015 at 17:55
  • My understanding of your comment is two possible solutions. 1) Fill the entire cavity (with no backer rod) with grout then seal the grout
    – C.Thomas
    Mar 13, 2015 at 21:49
  • 1
    Based on your advice, and my own research, I guess the best solution is to pack the entire gap with a wide joint mixture of sanded cement type grout ( with polymer additives) and after drying seal it with a penetrating sealer. Does this sound right?
    – C.Thomas
    Mar 14, 2015 at 15:06

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