Shower was redone about a year ago. At some point a crack slowly developed, through grout and a tile. The area is in the middle section, so tiles above and below and to the sides are fine.

What could be the cause? Is everything around it under strain, and it just erupted in the middle?

image below - red lines added over cracks

EDIT: another image with 3 steps - studs, cement board + redgard, start tiling

Also, I should say there are a few other grout cracks in various places. Bathroom is at corner of house, so it's an outside wall.

The reason for remodel was original drywall got wet and bulgy from soap holder falling off (and us not covering it up very well). Studs were a little moldy but seemed sturdy enough. Cleaned with vinegar and dried for a few days.

enter image description here

enter image description here

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    You'd have to tell us something about what's behind the tile.
    – isherwood
    Commented Jun 14, 2023 at 18:27
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    Well either there is no waterproof membrane and concrete board wasn't used or you have some huge settling issues with your house. It could be from a loose tile to thinset join but not usually in a fault pattern like this. If I were to guess I would say either the wall wasn't prepared right at all - could be too much distance between studs (doubt it) maybe there is just drywall behind and the drywall got wet and cracked because of that. That sort of cracking is not a good sign. Also is this wall on the outside of the house?
    – DMoore
    Commented Jun 14, 2023 at 18:28
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    Could be they used cement board but didn't do the joints correctly. That's moot: it needs to be redone and redone right. Commented Jun 14, 2023 at 19:15
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    Really do need more information about whether this is caused by the house settling/heaving. Is this an exterior wall? Are you on a hill? Is there clay under the house? Has it rained or been dry a lot lately? Do other doors around the house bind seasonally? Commented Jun 14, 2023 at 20:58
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    @AloysiusDefenestrate The electrical wiring is indeed buried in the wall. The main electrical panel is on the outside of the bathroom wall. Is that against code?
    – itchmyback
    Commented Jun 18, 2023 at 22:36

1 Answer 1


The good news is it is called flexing. The bad news is it is flexing.

The wall behind it was not done properly and it is flexing. If the tiles are on a drywall it will do that. It should have been a cement board. The grouts are the weakest point, but I have seen tiles crack as well, like you have. That is a clear indicator of flexing. More damage is to come.

  • In my house, it's not only just greenboard, but no joint tape was used between pieces.
    – DaveM
    Commented Jun 14, 2023 at 19:14

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