Shower pan installation with backer board

Discussion in 'Shower & Bathtub Forum & Blog' started by ruggles531, Apr 27, 2013.

  1. ruggles531

    ruggles531 New Member

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    Location:
    Ontario
    I installed a shower pan in my ensuite two years ago. The pan was a solid unit with a 1/2" lip around the edge. I installed it flush with the stud wall and put Hardiebacker 1/2" board on the wall, running it flush with the lip on the pan. This worked great and I was able to install my tiling flush between the Hardiebacker and the shower pan.

    I am now installing a shower pan in our kids bathroom. The unit I purchased for them is a fiberglass one from Maax. The instructions say to install the pan flush with the studs and to have backerboard sit flush on the lip of the pan, similar to my install above. My problem this time is that the lip is only 3/16" thick on the Maax pan. I wanted to use the 1/2" Hardiebacker again on the walls, but how do I run it flush with the pan? The only thing I can think of is firring out the wall studs for the pan area only to have the lip sit at 1/2" from the main wall stud. Below is the diagram from the Maax web site. I am planning on using Hardiebacker instead of their recommended drywall. Their diagram doesn't seem to take into account the fact that the flange/lip is only 3/16" thick

    Does that make sense? Is there a better way to do this?

    Capture.PNG
  2. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    post(s) deleted by John Whipple
    Last edited: Mar 17, 2014
  3. cacher_chick

    cacher_chick Test, Don't Guess!

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    Much like is done with most tub installs, the bottom 1/3 of the bottom row of tiles can "hang" over the edge.
    I agree with John though, installed as drawn, the water is going right through the wall and running down behind the pan.

    Neither tile or backerboard is to be thought of as a waterproof layer.
    Last edited: Apr 28, 2013
  4. ruggles531

    ruggles531 New Member

    Messages:
    4
    Location:
    Ontario
    In my ensuite I was told just to install the backerboard to the studs and tile right on top of it. I wasn't informed I should be putting a waterproof layer on. The Hardiebacker web site never mentioned using any. What is the recommended installation practice?

    Also, is it OK to just leave the tiles overhanging with a gap behind it in the pan, or should I shim the pan out?
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    While cbu isn't affected by water, it is NOT waterproof. There are several methods that work...put a vapor barrier (typically a sheet of plastic, or some roofing felt) behind the cbu and lap it over the tiling flange of the pan so any moisture that gets back there has a path into the pan; or, apply a topical waterproofing on the surface of the cbu - this could be either a liquid membrane or a sheet membrane.
  6. ruggles531

    ruggles531 New Member

    Messages:
    4
    Location:
    Ontario
    Good to know. I would have thought something like that would be mentioned on the Hardiebacker website. So, if I install the shower pan flush with the studs, put some poly behind the backer board and lap it into the shower pan, and leave the 1/4" gap between the backer board and shower pan lip I should be fine?
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
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    Location:
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    That is one accepted practice. When tiling, it is acceptable to cantilever the tile on the wall as long as more than half is properly supported...this would not be acceptable on a floor, but then you don't walk on the wall.
  8. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    post(s) deleted by John Whipple
    Last edited: Mar 17, 2014
  9. cacher_chick

    cacher_chick Test, Don't Guess!

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    The backerboard with no waterproofing will take longer to dry out between uses. Combine that with some soap scum, skin cells, etc, and you are that much more likely to have mold and/or mildew problems.
    Waterproofing the backerboard makes a lot sense, and I don't know why anyone would want to skip it.
  10. ruggles531

    ruggles531 New Member

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    Location:
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    Thanks so much for the info guys. That's some great information.
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