I was working on removing and redoing old grout/caulk in the guest bathroom for a house we moved into recently (built in 88, unsure if shower has been re-tiles since then). About 24 hours after I removed the grout line between the tile and the tub, I noticed some water beginning to pool around the bottom of the tile wall in one corner, along ledges of tub. One tile was somewhat loose and I pried it off to see what was going on. It looks like the tile was installed on green drywall? Behind the drywall is the lip of the tub. The drywall does not seem damaged, I can’t push through it or anything and it’s not crumbling. There is a bit of mold along the bottom but doesn’t look severe.

Does anyone have experience to know if a professional needs to come evaluate this further? I know tile on drywall is bad, but if it’s something that can wait a few years to redo then I will glue the one tile back on and defer the issue? Attached is a photo of where I pried off the one tile. No other tiles are loose

Since the drywall is not waterlogged I’m assuming there’s no damage to the framing of the house?

enter image description here

  • I removed the cost question since that's explicitly off-topic. The only way to get accurate cost in your part of the world is to get some estimates.
    – FreeMan
    Nov 30, 2023 at 13:04
  • tile grout is not supposed to keep water from sipping through. Whatever is behind the tiles are supposed to be able to deal with moisture and a small amount of water.
    – Quoc Vu
    Jan 3 at 19:41

1 Answer 1


That is typical 80s shower construction.

The green board is a moisture resistant board commonly used then but rarely now.

The mildew is the result of water leaching behind the tiles at the tub edge. You can clean it off as best you can.

There is no way to know exactly what is behind the walls. However what is shown in your pic simply indicates a loose tile has come off and does not show signs of a more extensive water infiltration.

If, as you have stated the walls are firm and no other tiles are loose, you can reinstall the tile,( use a polyurethane adhesive ),grout and caulk the bottom edge. You should be good for a year or two, maybe longer. However I would definitely put this project on my "to do" list. The frequency the shower is used will increase the urgency.

We cannot quote prices here. They differ by region, but honestly, taking out shower walls and rebuilding with cement board and new tile is actually pretty easy. Dirty, but easy.

  • I would be tempted to make my first attempt at using epoxy grout to waterproof the inside face of the tiling. Depending on the current tile's quality, that is.
    – popham
    Nov 30, 2023 at 18:22

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