I have had two instances of grout cracking in the past year, and both of them were with the same builder. One of them was on Hardibacker, and now this one on Ditra. Both of them are on a single layer of 3/4" Advantech. I'm not sure this guy is even going to be doing any more construction with the economy the way it is, but I'm thinking if he does, I'm going to strongly suggest he go with single layer plywood or a double layer of OSB.

Some of problem might also lie with the framers. If they didn't level that wall perfectly with the other walls, that could cause the problem. We've also had some pretty wide temperature swings over the past few weeks, and a crapload of rain. Don't know if those might be a factor.

Well today, I finally pulled up some of the tile that has cracks around the entire perimeter of each tile....AND......they are stuck down really well...nothing is loose...the Ditra is well bonded to the plywood subfloor...the tile is well bonded to the Ditra. I don't know what to say. It's as if the movement is sideways..and Ditra is supposed to address that issue. I may give up on the stuff in High Traffic areas. Lucky(or not) this is my brothers house. If it weren't I would be totally screwed right now.

Bri, have you mentioned this to anyone from Schluter? Maybe they could offer an opinion on the problem.

I haven't. I'm afraid my sister-in-law will find out the reps name...and..well......I don't want to be responsible for what might happen

Plus....I used modified thin set for everything..so, I just figure they'll tell me that was the problem. But now that I see the bond is fine...I think I will tell them.

Got another one.

This is one I did earlier this year. Three different areas of tile, and one travertine. Not one tile is cracked, but there are hairline cracks in different areas. Even the grout with the travertine is cracking. I figured if it was a deflection issue, the stone would crack too, but it hasn't, and it's on Ditra XL. They've installed cabinets, a stove, and a refrigerator on this travertine and it appears to be holding up okay, but the grout has hairline cracks. I'm about to my wit's end on this.

If I just knew what the problem was, I could address it, but I can't seem to figure out what's causing it.

Funny enough...I am doing a shower right now...the rest of the room is done already...many years ago...old ditra...with the ribs. I can take the whole floor out in one piece. Not one crack in the joints though. How weird is that?

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Any pics yet