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  1. #1
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    Oct 2007
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    Default What thickness cement board

    Can someone tell me if I should use 1/4 inch or 1/2 inch cement board (Hardybacker) when installing wall tile in a shower? Also should plastic sheeting or any other type of waterproofing be installed on the studs before installing the cement board
    Thanks
    Last edited by sodian; 10-21-2007 at 02:59 PM. Reason: remove mistake

  2. #2
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    Default Re: What thickness cement board

    Quote Originally Posted by sodian View Post
    Can someone tell me if I should use 1/4 inch or 1/2 inch cement board (Hardybacker) when installing wall tile in a shower? Also should plastic sheeting or any other type of waterproofing be installed on the studs before installing the cement board
    Thanks
    If that is going to be the only wall backing material you should definitely go to 1/2 the 1/4 is too thin.

    Applying a proper vapor barrier onto the bare studs before the wall board is a definite step that should be done.

    After installing the vapor barrier then the 1/2 inch backer board I would recommend a product called Kerdi waterproof membrane. The reason you put it on top of the backer board before the tiles is to waterproof behind the tile.

    Cement board is not water proof it will absorb moisture. The reason it's used in place of drywall is that it does get wet it won't rot or encourage the growth of mold like rotten drywall.

    Check these links :
    http://www.schluter.com/8_1_kerdi.aspx

    http://www.johnbridge.com/kerdi_shower.htm

  3. #3
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    Oct 2007
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    Default Re: What thickness cement board

    Thanks Canuk!! That's just what I needed to know.

    Steve

  4. #4
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    Default Re: What thickness cement board

    Steve ... you're welcome and good luck with your project.

  5. #5
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    Nov 2007
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    Default Re: What thickness cement board

    We stopped doing showers without the Kerdi System because of problems with them leaking. The Kerdi system is definatley the way to go. It goes over top of the durock and provides a 100% waterproof seal. With the money being put into showers these days, its well worth the extra money when you look at what you're getting. To reiterate what was said, you would need the 1/2'' for not only durability but to also match up flush with your sheetrock.

  6. #6
    Join Date
    Nov 2007
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    Default Re: What thickness cement board

    If I understand correctly, the Kerdi membrane is only needed over HardiBacker, not cementitious backerboard (CBB) like Durock or Wonderboard. No offense, but anyone getting actual leaks without it is definitely doing something wrong.

    The vapor barrier is only to minimize moisure bleed-through, and I just heard about some new CBB that has an impermeable backside seal coating of some kind; don't recall the name & haven't yet seen it aywhere, however. TCA specs used to call for fiberglas insulation behind a layer of tar paper, overlapped so any unlikely condensate ran down inside away from the batt and down to the tub lip. I always wondered where it was supposed to go from there...? But done right, water runs straight down the tile & grout, with no gaps to enter to then penetrate the CBB and wick or bleed through.

    I always did it that way (insulation, tar paper, Wonderboard screwed & taped, tile, and grout except 100% silicone in all corners, and NEVER got a call-back; and I think I might even be able to remember the definition of warranty work if I try hard enough... Let's see, now... Oh, yeah, now I remember... That's what I heard some other guys have to do sometimes... When they don't work the way I was taught. Sorry about that.

  7. #7
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    Default Re: What thickness cement board

    If I understand correctly, the Kerdi membrane is only needed over HardiBacker, not cementitious backerboard (CBB) like Durock or Wonderboard. No offense, but anyone getting actual leaks without it is definitely doing something wrong.
    Yep ... agreed also sheet rock.


    But for DIY there is a chance for something to go wrong so the CBB is just an insurance.

    To paraphrase : "You now have a thousand year wall in a hundred year house. And bragging rights to match."

  8. #8
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    Default Re: What thickness cement board


  9. #9
    Join Date
    Aug 2009
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    62

    Default Re: What thickness cement board

    1/4" is really for flooring when you are placing it over 1/2" plywood or OBX. The 1/2" hardibacker/durarock is for walling when that is the only material to prevent flex. For a shower I would also only use a water proof membrane over top of the hardibacker. The worst that happens is you wasted a few bucks and an hour or two of your time putting it up before the tile. At best you prevented a serious moisture/mold issue.

  10. #10
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    Default Re: What thickness cement board

    Schluter guarantees kerdi to be waterproof and they encourage its use directly over drywall, although many people use Durock anyway (belt and suspenders). I personally hate hardibacker, as it absorbs too much moisture; it draws the water out of the thinset too fast.
    The Schluter foam shower pan/kerdi system is awesome. And don't forget the Ditra on floors. It is insane to use a CBU under Ditra on the floor, unless you need to make up the height.
    S_M
    Remove not the ancient landmark, which your fathers have set.

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