groutrepairshowertile
Just moved into this house a few months ago, and noticed the stub wall in the shower that holds the controls has cracked grout.
I'm guessing that somehow water got in behind the tiles and started to swell the supporting studs, which blew out all of the grout in the area.
What should I do to fix this?
You can see the tile is separating perpendicular to its surface.
Here too.
I recently built a shower using this same type of grout, but a different color. The matching silicone caulk I used was suitable for wet locations (picture below). I used this caulk in the gap between the vertical shower corners but I used up the one tube I ordered from HD and used clear silicone caulk along the horizontal shower to base gaps, and the vertical shower to adjoining walls wood trim. In the gap between the shower tile and shower glass I also used the clear silicone caulk. It all looks really nice now.
Nothing really bounds well to small pieces of loose thinset. The problem is that the thinset that is adhered under your tile isn't in one stable piece. Meaning that even if you add more thinset to a band of loose thinset it probably won't hold long, it certainly won't hold long term.
I suggest you cut your loses. You have had someone replace the tiles. I hope they told you they wouldn't last. For one I would have never just replaced your tiles. It is just too obvious that there would be issues really soon, since you are doing the same thing that just broke. I suggest demoing tile and doing it right. By the time you try to do 4-5 rounds of touch up you will be at the same amount of time than just redoing the floor. I mean there are instances where a plywood subfloor for tiles would conceivably work and may last years but you know that yours is not this case so why bother gluing the tiles down? They will come up, more tiles will come up, you will have grout crack everywhere. [And I am not a big demo and do it perfect to last 200 years Mike Holmes type]
Best Answer
It looks like the problem is not just the grout (which fills the gap between tiles) but also may be the tile adhesive is separating from the supporting structure (possibly plasterboard/drywall).
You can remove grout from between tiles using a variety of tools designed for this purpose. Then you can re-apply grout (and sealant if needed)
It seems likely that water has penetrated that structure, it might be best to open it up and assess what damage has been done and how the water got in.
In your case you may need to remove all the tiles, repair the supporting structure and re-tile. It's the only way to get the tiles to align neatly at the corners.