This crack is by the back door and goes through two tiles as shown and then follows the grout line to the right and then down the immediate perpendicular grout line. It stays in the grout and does not affect another tile as of this time.

This crack is the one by the room I removed the carpet. As shown, it bends through the first tile and continues through the next tile.

This photo shown the concrete below the tiles.

Could be voids under those tiles. Try knocking on the tiles to see if there are any hollow spots. Also, a decoupling membrane underneath would have helped. As long as you have some replacement tiles, might just do that and see how it goes.

The last pic shows they had bad coverage with the thinset. Just replace the bad tiles. (Probably will happen with some other tiles over time.)

This post was edited by homebound on Fri, Oct 25, 13 at 10:44

Thanks for your response. I tapped around each tile and only the one next to the room that I took the carpet out sounded hollow. The other two areas I couldn't hear a difference when tapping all around the crack.

Seems the cracking is on the vertical and not the horizontal.

Don't worry so much about the slab.

The framing is moving.

Cut the grout at the cracks now and see how far it goes.

Give it time to become stable and replace the damaged tiles.

Time is your friend here.

Good Luck.