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So after hosing down the bathroom, I started to hear some cracking. I looked at the tiles and they were bulging out from the center. I guess water got into the top and loosened the tiles.

Wall Close-up Close-up 2

I started to gently remove the very loose tiles by hand, so they wouldn't fall and break. The wall is concrete and the remaining adhesive is pretty rock hard. Not sure if I should remove it all and re tile or is this fixable?

  • It is fixable. Try to pull any tile from the wall. It shouldn't budge. Scrape dried thinset off the wall and mix a correctly proportioned water to thinset batch. It should remain on a trowel when turned upside down or have the consistency of peanut butter. – ojait Sep 1 '15 at 3:39
  • The thinset on the wall is pretty hard. The tiles that came off didn't seem to stick very well since the back was pretty clean. What do you recommend I use to scrape the thinset on the concrete wall since it is pretty much rock hard. – Rick Sep 1 '15 at 3:46
  • Also check the backing material. I noticed a crack running vertically under the window corner. If the backing was floated with a cement mix check that it hasn't been compromised. The crack may not be the primary reason for the tile not adhering, but it may have contributed. Look for bulges and large gaps in the backer (small hairline cracks can be normal) I hope it was just those few tiles that came loose and not the whole wall. – ojait Sep 1 '15 at 14:20
  • The dried thinset should be fairly easy to remove from the wall (at least the trowel ridges will). I've used: a margin trowel. an old wood chisel, wide flat-head screw driver, pry bar... It may be difficult to only remove the thinset and not gouge the backer, but once you're in the flow it will be easy. – ojait Sep 1 '15 at 14:27
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    It looks like the installers let the thinset dry too much before sticking on the tiles. For walls, it is a good practice to apply a thin layer of thinset to both the backing and the tile. This is called back buttering. It will help prevent them from coming off again. – Jason Hutchinson Sep 3 '15 at 18:49
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I can see the ridges left by the installers notched trowel. Look at the back of any loose tiles. It should have thinset on at least 80% of it's back. I'm guessing the thinset wasn't mixed correctly. If it is to dry the tile does not get pressed into the notched adhesive so as to form a mechanical bond. You can check if the tiles are affixed properly by giving them a slight rap with your knuckle. You should hear a dull sound. A hollow or "ting" reverberation indicates a void or low spot were the thinset isn't fully supporting the tile.

  • Most of the tiles that came off were pretty clean on the back. There is a lot of hollow reverberation. – Rick Sep 1 '15 at 3:44
  • no dried thinset on the back of the tile means they weren't affixed properly and/or the thinset wasn't mixed correctly. – ojait Sep 1 '15 at 3:51
  • The tiles that are bulging out are held on by the grout. is there an easy way to remove them without having to having the other come out? – Rick Sep 10 '15 at 11:52
  • @Rick- the fact is that if the grout is the only material keeping the tiles on the wall it may be wise to remove them regardless of whether they appear securely fastened to the wall. – ojait Sep 10 '15 at 17:47
  • @Rick- And to remove any tiles that are about to fail try a margin (square shape) trowel or a pointing trowel. The off set handle makes it easy to pry the tile away. Also a putty knife or any wide bladed hand tool. – ojait Sep 10 '15 at 17:52

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