Shower tub tiling flange and bowing backerboard

Discussion in 'Shower & Bathtub Forum & Blog' started by KSHandyMan, Jun 18, 2007.

  1. KSHandyMan

    KSHandyMan Junior Member

    Does anyone else constantly run into the issue of having the wall hung concrete backerboard bow inward where it overlaps the tiling flange on shower pans or tubs? Granted it's not much but it is sometimes noticeable.

    I'm doing my shower now and I'm thinking I may shim the wall to bring it flush with the flange so I can just install the backerboard with no bowing. Any hints or tips?
  2. Cass

    Cass Plumber

    That small amount won't make any difference. Once you tape and thin set the seams then install the tile nothing will matter.

    On the other hand if you will sleep better at night because you shimmed it..........have at it.

    They will be mighty thin shims.
  3. yes, block or shim.

    bowing -- do you mean between the studs? That would mean it bows anywhere on the wall, not just in the middle segment of the tub space.

    Depending on the size of the tiles, and how they are laid out, even a 1/16" overlap, underlap, lippage, is visible and can be a permanent source of frustration instead of pride.

    Cement backerboard does bow inside the 16"O.C. space between studs. I have put blocking right across the entire tub length.

  4. jimbo

    jimbo Plumber

    San Diego
    If you mean bowing out at the bottom where the backer overlaps the tub flange, that is not good and the standard installation calls for furring out the studs.....something like 1/4" lath usually is about right.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    New England
    Another alternative when setting the tub is to notch the studs so that the flange is flush with the outer face. This can help keep the cbu flush with adjoining drywall. Either method works, just produces slightly different results. The tiling flange on some tubs can be quite thick.

    Depending on how high that flange is, and the size of the tile you are using, as long as the vapor barrier laps over the flange, you might be able to stop the cbu above the flange. This works with larger tile, but not with smaller ones. You want at least 2/3 of the tile supported by the can backfill with thinset on the flange when setting the tile, and caulk the bottom edge.
  6. glad to know what he meant. This is a great site, where nobody feels it necessary to correct a previous poster; they just give the right information instead. Now i get it.

  7. KSHandyMan

    KSHandyMan Junior Member

    That's not a bad idea. I've worked with the slight bowing that overlapping the flange has created in the past but this time I was trying to avoid that. I might be able to use a chisel and just take off about 1/8"-1/4" off the stud so the backerboard will lay flat across the flange. Thanks for the suggestion.
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