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I had a new en-suite bathroom installed in my oversized bedroom a little less than a year ago. Today I noticed when walking on a certain tile i hear a little sort of pop sound. On closer inspection it appears the grout is cracked as seen in the picture in that area and a few others throughout the bathroom.

I don’t know whether this is a subfloor issue but I’ve been freaking out about it because that seems like a nightmare to fix.

Anyone with suggestions on what it might be, what it might take to fix, and how I can hold the contractor responsible assuming he messed up?

He said he did everything right — new plywood subfloor nailed down every 6 inches (same as tiles), an underpayment, and Schluter Ditra, with each tile back buttered and carefully put in place with the right thinset.

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  • Try to lift the tile and take photos. Are there any cracked tiles?
    – Martin
    Oct 24, 2023 at 11:23
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    The "holding contractor responsible" is out of scope for thise site. We are DIY, not law.
    – Martin
    Oct 24, 2023 at 11:23
  • Have you talked with the contractor about it?
    – FreeMan
    Oct 24, 2023 at 11:36
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    Do you remember if the contractor installed any backer board under the tile? It would have increased the tile floor elevation relative to adjacent rooms.
    – popham
    Oct 24, 2023 at 15:50
  • Is that natural stone tile? Or is it some kind of ceramic? If ceramic, do you recall if it was porcelain?
    – popham
    Oct 24, 2023 at 15:51

3 Answers 3

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Most likely what you have is a tile with an uneven application of thinset. The popping sound is the tile swinging. You can DIY it or have a handyman do this: remove the tile, scrape thinset, apply new, reset tile, grout.

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  • The problem ID is probably correct, the resolution, maybe not. This sounds like a new install - the original contractor should take care of it. ;)
    – FreeMan
    Oct 24, 2023 at 11:57
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If you look at the various options for tile over wood floors in the TCNA Handbook, every option calls for some kind of underlayment on top of the subfloor. Engineered backer board products on a floor aren't going to debond from ceramic tile like yours unless the installer was grossly negligent. Pulling up the tile will decide that possibility immediately. If the thinset beneath has squished blobs of thinset or uncollapsed ridges of thinset, then you have a workmanship problem. (In the case of stone tile, a failure to back butter is a poor workmanship possibility, but your images clearly establish that yours is ceramic tile.)

Instead of an engineered backer board beneath your tile, there could be a plywood underlayment. The TCNA Handbook does have plywood underlayment options, but successfully implementing one is a little trickier than the engineered backer board products:

  • The underlayment plywood must be exterior grade so that the glue isn't susceptible to water and
  • there's a special thinset for applying tile to wood underlayment. This thinset must satisfy ANSI 118.11. It'll say so in the fine print if you can't find the right stuff from "good for wood!" marketing material.

Using the wrong thinset for plywood underlayment is an easy mistake to make, where this would probably be your best-case-scenario. Spot fixing tiles as they fail with an ANSI 118.11 thinset will solve this problem eventually.

There's nothing in the TCNA Handbook for tile directly over subfloor. In all likelihood a subfloor's plywood isn't going to be exterior rated, making it susceptible to water. A subfloor typically will be designed to the International Residential Code's maximum deflection of L/360, where that L/360 is obviously inadequate or else there would be a TCNA Handbook recipe for tiling a naked subfloor (put on some underlayment, subfloor--have you no decency?). I suppose it's possible that a specific naked subfloor is much stiffer than the International Residential Code's L/360 (3/4" OSB subfloor over a 16" joist layout, for instance). Maybe the exterior grade glue isn't actually that important. It's possible that spot fixing debonded tiles with an ANSI 118.11 adhesive could fix a problem with tile debonding from a plywood subfloor.

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What you are hearing is common when newly installed tile experiences normal seasonal temperature changes.

Since there is no cracked tile, ( that you have told us about) and the cracking is only between the grout and tile, I have to believe the subfloor is fine.

In many cases this happens in the worst measure after the first seasonal change and is less after that.

The usual way to service this is to remove some grout where the cracks are and regrout. In some cases, where the grout cracks are prominent, it is advisable to add some liquid polymer to the grout when mixing.

The bottom line is that this is not a sign of any major issue.

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