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Thread: Cultured Marble Shower Base Install

  1. #1
    DIY Junior Member winklebe's Avatar
    Join Date
    Oct 2009
    Cleveland Ohio

    Default Cultured Marble Shower Base Install

    Hello all,

    Looking for a little advice, I am going to be installing a solid piece single threshold shower pan. It is produced by a company here in Ohio called Rainbow.

    The specifics of the project are - the Bathroom is currently gutted to the studded walls and a 3/4" OSB sub-floor. I plan on tiling the walls of the shower and the floor of the bathroom. I will be placing Backer Board on the walls in the shower and the floor.

    The manufacture says that the base is simply placed in position and shimmed as needed (no thinset, ect).

    Can anyone offer some advice on weather I should continue the Backer Board that I am placing on the floor to be under the base, or should I place the base on the OSB then run the Backer Board to the threshold. I was thinking that if I ran the Backer Board on the entire floor and into the Shower stall it only adds about 1 additional sheet and would offer a level of protection if water gets between the Base and the tile at the edge of the threshold.

    Also, as an off beat question - if you had the option, would you run tile completely under your vanity or would you place the vanity on the sub-floor then tile to the edge? (vanity is 6' x 22" so it ass like 12 Sq ft of tile at or about 60 bucks)

    Thanks in advance for all the help

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    Aug 2004
    Bothell, Washington
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    I prefer to set the shower pan first, and then run the flooring up to it.
    This way you can shim if needed, and it doesn't show a gap at the front.
    The flooring will cover any gaps.
    You have to set the pan level, but the floor may be anything but level.
    Never assume an old home has level floors.

    That also means that when you step from the floor to the pan, the height is closer.
    If you set the pan on the finished floor, you will be stepping up.

    Setting the vanity first or second, you can make an argument either way.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
    Join Date
    Sep 2004
    New England


    Cement board is NOT waterPROOF, it is just not degraded by being wet. So, do NOT consider it any protection for the floor or the walls in the shower. The main reason for using cbu is that it expands and contracts nearly the same as tile, so provides a good substrate to hold it in place. The nails or screws you use to attach it are what holds it to the floor or wall. Also, ensure you put a vapor barrier behind the walls of the shower and lap it over the tiling flange of the shower base. You don't need to caulk it in place, when you add the cbu and tile, that edge would be hidden. Prior to tiling a floor, ensure it is sturdy enough to support your tile. To do this, you need to know the size, dimmensions, type of wood, and length of the unsupported joists, and their spacing. Do NOT assume your floor is stiff enough to support tile, it may not be. Note, the length is NOT the size of the room, it's what's holding it up underneath the walls, and could be much longer than the size of that room. Check out www.johnbridge.com for help on tiling.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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