Layering plywood on shower walls

Discussion in 'Shower & Bathtub Forum & Blog' started by Milesmoony, May 17, 2019.

  1. Milesmoony

    Milesmoony New Member

    Joined:
    Apr 21, 2019
    Location:
    Seattle
    I’ve removed the shower panels making up my surround. Someone had used some kind of coated hardboard, glued onto the plywood walls around the shower. The hard board was starting to deteriorate so I ripped it all off. The plywood is in great shape and would be a pain in the but to remove. Only problem is that the plywood surface is covered in dry glue, it’s not a smooth surface at all. I’m planning on gluing up some nrp panels with liquid nails for my new shower surround. I was thinking a solution could be to screw 1/8” plywood all around the plywood walls, and then glue the nrp panels over that, caulk the moulding in place and done. What I’m concerned about is condensation forming between the 1/8 plywood and the plywood walls, leaving an environment for mold. Thoughts? Suggestions? Is this a valid concern? Thanks for your advice
     
  2. ImOld

    ImOld Octogenerian

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    In the rumble seat
    I wish I had taken some pictures of showers where the moisture and black mold had eaten away not just the drywall behind the tile/surround but also the 2x4 framing. I mean no more bottom foot or two of the studs. Remove all the crap back to the studs and put in cement backer board.
     
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  4. cacher_chick

    cacher_chick Test, Don't Guess!

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    My preference would be to remove the plywood, and I cannot imagine many good reasons not to. If you must, overlay the plywood with 1/4” cement board and finish the corners properly before applying a couple of coats of topical waterproofing like redguard. If I wanted a nice shower, I would do it right and finish it with tile.
     
    Last edited: May 19, 2019 at 7:48 PM
  5. EBrown22

    EBrown22 New Member

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    Hey cacher_chick,
    What would you prefer other than plywood?
    Which material will give proper waterproofing?
     
  6. cacher_chick

    cacher_chick Test, Don't Guess!

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    Cement board would normally be installed in a shower or tub surround. There are several brands of products designed to waterproof it. Redguard is common here. Your could also apply a sheet good like Kerdi, but that might be overkill if you are not going to tile.
     
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
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    Retired Systems engineer for defense industry.
    Location:
    New England
    It sounds like you're planning to install waterproof panels for a shower surround that need support from behind. Most any 1/8" stuff you might try to install over the rough surface of the ply will not really flatten things out and would end up wavy once you attached it.

    A waterproof panel should not need any waterproofing behind it. I'd probably tear the ply out, but if you can afford the thickness, you could add another layer of ply to flatten things out if it were say at least 3/8". Note, 3/8" ply is hard to find that is actually flat, though, so 1/2" might work better.

    If you have a belt sander or a big disk sander, it MIGHT take the glue off fairly quickly. Some glues, though, will just gum up the sandpaper...depends on the type.

    If the panels are not waterproof, then the ply behind should probably come off. If you end up tiling, you want either a moisture barrier behind the cement board (CBU) or waterproofing on top of the CBU, not both, or you'd trap moisture in the sandwich. Keep in mind that neither the tile nor grout is waterproofing...it's a decorative, wear surface, and moisture will get behind it.
     
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