Cement board vs purple gypsum board for small repair

Discussion in 'Shower & Bathtub Forum & Blog' started by Hughpe, Feb 11, 2019.

  1. Hughpe

    Hughpe New Member

    Jan 24, 2017
    Water leaked from corner of tub- from taking showers-onto green board drywall and ruined it. I’ve taken steps to mitigate the leakage but have no doubt that will occasionally get wet. It’s a small repair but probably a pain. Would cement board or purple gypsum board be a better substitute for the rotted drywall. Thanks
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    The purple stuff tends to have a water resistant coating on it, but the guts are still gypsum and you'll be poking holes in it to attach it!

    CBU won't be damaged by being wetted. To get the surface prepped, consider setting mud versus the premixed stuff. YOu don't have much time to install it, but it won't soften again if it gets damp like the premixed stuff. Mix small batches.

    FOr reference, I'd take a level and check the rim of the tub. It should have a slight slope to it into the tub and not slope outside. It could just be the shower curtain isn't well positioned, or the door, if it's configured that way, but more often than not, it's the tub was not leveled properly during installation.
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  4. Stuff

    Stuff Active Member

    Mar 7, 2013
    The bigger issue isn't the wallboard but the waterproofing that failed. Cement board is OK to get wet but will let water pass through and you'll eventually have a moldy mess in the wall. Lots of 1950's bathrooms around here were covered with glued on plastic tiles as they didn't think people would actually use the shower. Then a new family moves in and tiles start popping.
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