My contractor used mold resistant drywall for ceiling in shower stall; ceiling will be tiled. The stall will be surrounded by frameless glass and there will be about 4" gap from ceiling and the glass. Should I tell contractor to replace drywall with cement board, or is mold resistant drywall fine in this case with liquid waterproofing on it? Cement board will be used for shower walls.

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3 Answers 3


I would want cement board up there, but not for the reason you may expect. I wouldn't want hard, heavy tile hanging on a thin layer of paper regardless of moisture concerns.

It's not terribly expensive and a fairly easy fix. I'd ask for cement board.

  • @rtaft wouldn't the schluter membrane applied with thinset tie the paper to the fleece backed membrane? Just saying schluter explicitly showing that this is ok in a ceiling application.
    – redlude97
    Commented Jan 27, 2022 at 18:22

My shower was originally done entirely with drywall, not a scrap of cement board in sight. It was installed in 1976 by the then-owner of the house and lasted until around 2012 when someone stumbled in the shower and kicked the wall a little too hard.

Water falls down, well-done tile and caulking shouldn't let any water through regardless, drywall for the ceiling should be fine as long as you're not in the habit of taking hours-long hot, steamy showers with no vent fan. (in which case all of your drywall is likely to suffer, whether it's in the shower ceiling or not.)

But cement board is better, so if you're willing to pay for it, then by all means do that instead.

  • You might mention the type of tile. Light 4x4 tile is one thing, the thick 12x12 and larger tile you often see today is another. Chances are drywall will hold, but if given the option....
    – isherwood
    Commented Jan 27, 2022 at 13:59
  • @isherwood if one covers the wall, I don’t see why 4x4 would be different to 12x12 (ignoring any thickness differences)?
    – Tim
    Commented Jan 27, 2022 at 23:28
  • 1
    @Tim It would be thickness differences that would matter. I don't remember how thick the old tiles were. About a quarter inch I think. Paper is actually pretty strong as long as the force is distributed well, that's how corrugated cardboard boxes can hold large amounts of weight.
    – Perkins
    Commented Jan 27, 2022 at 23:58
  • 1
    I most definitely do not recommend this answer - in my house the previous owner hacked together a shower using nothing but drywall beneath the tile; on one occasion I noticed that the tiles are loose and it turned out half of the drywall behind rotted away because of tiny cracks between the tiles.
    – xxbbcc
    Commented Jan 28, 2022 at 15:35
  • Tiles might not let water through, but the group between them certainly will.
    – Woodford
    Commented Jan 28, 2022 at 16:27

Last I looked cement board and drywall prices are low and comparable enough to not make a dent in your budget (looks like your ceiling is $10-20 of cement board at most, including screws). I did my first shower ceiling with cement board, it worked great.

As for isherwood's concerns about a thin layer of paper not holding the weight of tile, check out Schluter's Kerdi membrane. A thin layer of water proof orange membrane, mortared to that thin layer of paper, works amazingly well. I did my last project with it.

Drywall showers, as mentioned by Perkins, are known to mold because grout ages and cracks with time - even well done tile. I consider Perkins lucky the walls weren't covered in mold; not recommended.

I am a DIY guy, neither a contractor nor a professional nor do I have any affiliation with Schluter.

  • I'm not sure your anecdotal, short-term evidence is terribly convincing that it's a good strategy. It'll probably hold, but the odds are better with cement board. Does Schluter recommend that application?
    – isherwood
    Commented Jan 27, 2022 at 14:00
  • I'll definitely replace sheetrock with cement board, cost is not a concern here at all. It's probably under an hour time worth of work here.
    – positron
    Commented Jan 27, 2022 at 14:25
  • I wouldn't suggest building a whole shower out of drywall. My only point was that, if you're doing it right, the backing material's susceptibility to water shouldn't actually matter particularly much. Something more water resistant than drywall is definitely a better choice now that the prices are roughly the same just because it gives more margin for error. But it may not be worth the expense of redoing a ceiling given that all the protection factors will be as much in your favor as possible.
    – Perkins
    Commented Jan 28, 2022 at 17:43

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