I recently noticed horizontal cracks in the bathroom tile, running almost the entire width of the shower/tub enclosure back wall. We have had issues with crown molding separating ever since we installed a new HVAC system and we are considering adding a humidifier to the system. It appears that the material in the house may be drying out.

The discoloration in the grout is because it was wet. I've never seen grout like this until I moved here. We also have some separation of the back shower wall from the sides. But now that summer is here, and it is more humid, the cracks and separations are less noticeable.

I'm just concerned that this may be an issue with the new bathroom. Any thoughts?

large view of cracked tiles/wall

Close view of cracked tiles/wall

  • 2
    I'm more concerned that it might be an issue with your house. Cracks along entire walls mean that things which should not be moving, are. That can be VERY bad, depending what the root cause is.
    – Ecnerwal
    May 29, 2015 at 1:59
  • What is the height (1) above the floor, and (2) above the start of the tile by the floor? I'm interested in whether either of these are 4'. May 29, 2015 at 4:18
  • Thanks for responding. We had an inspector check the house last year who advised that the cracks were basic settling and nothing to worry about. the height of the crack above the floor is about 51 inches. And it is over the tub. About 37 3/4 inches up from tub.
    – Wil Hall
    May 29, 2015 at 10:30
  • 2
    I'm guessing that's the seam of a backerboard, so yes, it's either basic settling, or more substantial movement. You'll know more when you do the reno. May 29, 2015 at 14:18
  • If the house is wooden framed (99% of houses around here); then it will expand and contract annually with moisture changes (we live right on the Atlantic coast and heat with wood in the winter; so we see relative humidity changes as high as 50% or 60% every year). Make sure your contractor understands this problem. There are many design decisions you can take to allow for the movement (e.g. chimneys don't move so allow space around the thimble thru the wooden wall). See: Bruce Hoadley "Understanding Wood"
    – ericx
    Nov 18, 2015 at 16:59

1 Answer 1


I had a similar problem in my house, and I started digging out and replacing the cracked tiles. That turned out to be rather tedious, as the tiles were well attached to the wall and there was much collateral damage.

Ultimately my diagnosis was as Aloysius Defenestrate hints at in the comments. The cracks were along a seam between two backer boards. In my case concrete board below, green board above. The boards where not obviously taped at the seams or supported by any horizontal lath boards between the studs. Either one might have mitigated the problem. Inevitably I ruined the underlying backerboard removing the cracked tiles, but I could see the underlying structure.

My repairs involved pre-drilling and toe-screwing some lath boards as support. and layering up new backer, thinset and tiles.

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