>I can find no evidence of water damage in the adjoining wall.

Should have clarified that there is no plumbing in there. On the other side of the wall is the nook for the clothes drier, another wall past that with no plumbing, then the guest bath, so water would have to travel far to pool there.

Sounds like the adhesive has separated from the slab, because of poor prep.

If it sounds hollow, it's loose.

Not necessarily (poor floor prep, although it's a possibility).

writersblock-- let me ask you-- did they grout the floor to the baseboard, or did they caulk it? Also, by any chance, are you in Fla.?

"tickety-boo"? :-)

(must be a technical term.)

Yes, I'm in FL, Bill. Caulk.

The reason I asked about Fla. (the crunching is what gave it away) is there's an inspector I know who goes all over the country (a gentleman named Dave Gobis). He's literally one of the top names in the industry, as in one of the guys who helps write our specs. He's mentioned several times about the literally hundreds of installations PER YEAR he's inspected all over the state that have all been installed with unmodified thinset, which just doesn't have enough grab to hold onto a concrete slab without additive, all of which the thinset begins to crumble after a couple of years and the floor comes back up. I know this to be true from personal experience, because when I lived in Homestead, all the tile guys I worked for down there all used unmodified thinset. Every one of them. I didn't start using modified thinset until I went into business for myself, and even then it was tough bidding against other tile contractors when my thinset's running 20.00 a bag versus them paying 5-7.00 a bag. Just one of the reasons tile installations, for the most part, are so cheap down there.

Several years ago I went to FL to help out a buddy who had tile releasing from his slab, along an exterior wall.

When I started digging around in the other rooms I found a few other tiles that had released, they were all along the same wall.

They were on the south wall and southwest corner wall of his house. My best guess was that the afternoon sun was causing a bit more thermal stress on that south side of the slab, and the stresses cause the thinset bond to fail and the tiles to pop.

The tiles were set with unmodified.

While I was taking lunch one afternoon, there was construction going on a few lots over, the guys were using BEACH SAND and mixing that with portland for mortar to set CMUs.

Oh, how concrete loves salt, eh?

Thanks, guys. That makes a lot of sense, since the owner at the time did everything as cheaply as possible (we're having to replumb, too, although they had done it about five years before we moved in). Believe me, if the guy normally did use modified thinset, I'm sure they would have griped like crazy about the cost till he said, "on your own head be it."

Well, it's actually not that big a deal. I'd already known it was likely that we'd need to redo the whole downstairs when we do the kitchen since there's very little extra tile--not enough to cover the areas they left out+the changes we're making. So now I just know that's not a "maybe" anymore.

Is there anything we can do temporarily about the ones that are already loose, since I don't know how soon we'll be able to start work?

Oh, and when we're ready to do the real deal--know anyone good who works in the treasure coast area (Stuart, pt st lucie, vero)?

Pull up the tiles, clean em up with a grinder, and then go to Lowes and buy a bag of Laticrete Multi-purpose thinset, and reset them. You'll need a hammer and chisel next time.

Thanks!

I know a couple of people from Jax, if that's close enough.

Well, they probably wouldn't think so--it's about four hours from here. We're nowhere near ready to start yet, though, so maybe I'll ask again when the time rolls around.

Thanks, though.