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  1. #1
    Join Date
    Feb 2012
    Posts
    3

    Default Tiled tub surround and cement board depth versus existing walls

    I'm attempting to tile a tub shower surround. I have completely removed all drywall on the walls around the tub except for from ceiling to about 2 ft down the wall. The existing drywall plus the plaster is 3/4" thick. The cement board is 1/2". Can I place 1/4" Luan behind this 1/2" cementboard to make up the 1/4" depth? I was told at my local home store that this is ok but I'm concerned about moisture between the Luan and stud walls. Note: this is for inside walls, no walls are outside perimeter walls. If I use the home stores recommended method do I use a roofing felt or plastic barrier behind the Luan? Is there a better way to make up for this depth issue without removing all existing plaster and drywall?

  2. #2
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,081

    Default Re: Tiled tub surround and cement board depth versus existing walls

    If you want your new cement board flash with the existing wall, then you have the right approach.

    Search past postings about this subject and you'll see that you could use tar paper (it's called 60 minute paper, thinner than roofing felt) between the cement board and the 1/4" luan. Fastening is important, follow directions accurately.

    Your last question puzzles me: you stated that you have already removed the existing drywall and plaster, didn't you?

  3. #3
    Join Date
    Feb 2012
    Posts
    3

    Default Re: Tiled tub surround and cement board depth versus existing walls

    I have removed all existing drywall around the tub except for from ceiling and walls down about 20". The depth (width) of the remaining drywall is 3/4" thus I need 3/4" in cement board. My local home store only sells 1/2" cement board hence the reason for my question. I want to make up for the 1/4" while still keeping existing drywall/plaster in the rest of the room. I'm planning on using 1/4" luan and 1/2 cement board to make up for the 1/4" difference. My question was whether I'll have an moisture issues with using this method.

  4. #4
    Join Date
    Dec 2010
    Location
    Houston Texas
    Posts
    2,360

    Default Re: Tiled tub surround and cement board depth versus existing walls

    CBU (cement boards) are not water proof. They aren't damaged by water, but then neither is a sponge.

    To waterproof the walls, there should be some waterproofing method everywhere the tile is, at least up to the height of the shower head. You can use tar paper or sheet plastic directly over the studs, then lap the sheeting over the tub flange. Your CBU can be nailed over that. Another choice is to use a surface waterproofing which can be applied over you old wall surface and the new CBU. Surface waterproofing comes in a liquid such as Hydroban, Red Guard, Hydro Barrier. Surface waterproofing can also be a sheet product such as Kerdi, Nobleseal, or Dalseal.

    The tiling and bathroom renovation Pro's at the John Bridge Tile Forum can give you great, speedy answers and you can post pictures.

  5. #5
    Join Date
    Jan 2008
    Posts
    1,096

    Default Re: Tiled tub surround and cement board depth versus existing walls

    I think what you're needing is to know if the luan is OK- yes it is, but any 1/4" furring, or even sistering spacers besides the studs will do. Water barrier goes over that, then tileboard, then tile. The idea of the waterproofing is to protect things water will damage like framing, so that's where you put it. The 1/4 luan will not add substantial structure so it's not needed between studs but it won't hurt there either. If ripped into strips one sheet will likely do the whole shower- a little labor traded for money not spent which can be used elsewhere!

    Phil

  6. #6
    Join Date
    Feb 2012
    Posts
    3

    Default Re: Tiled tub surround and cement board depth versus existing walls

    Thanks for the info. Much appreciated.

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