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Thread: Wonderboard x2... okay?

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  1. #1

    Default Wonderboard x2... okay?

    So... I was cleaning my shower Saturday and cleaned a little too hard... I pushed a couple tiles right through the (wet, rotten) greenboard it was glued to. I ended up taking that whole section of wall down. The original construction was studs, 1/2" sheetrock, 1/2" greenboard, tile.

    I added extra studs (there was only one in the ~30" span of wall), and I'm wondering.... is it okay to use two thicknesses of 1/2" Wonderboard, instead of sheetrock plus Wonderboard, behind the 4" wall tile?

    One sheet of Wonderboard would be enough, as opposed to buying some Wonderboard and a sheet of sheetrock.

  2. #2
    Plumber jimbo's Avatar
    Join Date
    Aug 2004
    San Diego


    I think I would just fur out the studs so that one layer of 1/2" cement board will land where you need it to be

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Neither greenboard nor drywall should be used anywhere in a wet environment! You saw what happened, and it could be worse - lots of mold can rot out the structure behind. Any version of cbu should be okay, but the recommendation is to put a layer of vapor retarder behind it on the studs (plastic or roofing felt). Lap that over the tub's tiling flange. Caulk changes of plane, do not grout.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4


    It wasn't as bad as it could have been. The greenboard was bad, but the wallboard behind it, while soft, was still white and not discolored. The wood behind it looked brand new.

    Anyway, thanks for the suggestions. I think I'll stick to the original plan and put up 2 thicknesses of Wonderboard. I already have the stuff and don't plan on using it for anything else. I got the longest screws so they should stay in place okay. The roof felt is a good idea!


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