Installing shower tile question

TresK3 Posted By TresK3, Dec 8, 2018 at 10:41 AM

  1. TresK3

    TresK3
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    Jul 12, 2007
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    The never-ending bathroom remodel may actually be approaching completion! I'm finally tiling the shower.

    I tiled the floor of the shower with a flat, natural stone mosaic. Now I'm doing the side walls with a 9x12 white tile, laid in a brick pattern. Because the bottom tile is stone, it doesn't give a perfectly smooth surface for the wall tile to land on. There's a small gap between the wall and floor tile (about a 1/16", depending on the height of the stone). Now I'm wondering what to fill this space with? I could squeeze grout into this joint between the wall and the floor or use a high quality silicone caulk. I'm leaning towards the caulk because it can flex a little, but I'm worried about how long it will last.

    If it matters, the foot of the shower is on an outside wall, the back (long side) is against an unheated attic, and the head of the shower is along a closet.

    Thanks for any thoughts, suggestions, ideas or experience with this.
     
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  2. Wooden Head

    Wooden Head
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    A couple of questions.
    What have you used for backer for the tile?
    What have you used for waterproofing the backer?
    What is flexing and why?
     
  3. TresK3

    TresK3
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    The backer is cement board. I don't remember the brand - it was either Durock or Permabase (I've used both at times). The shower base is a KBRS one piece unit. I used the KBRS polyurethane caulk at the joint between the cement board and the shower base, but it set up much faster than I expected and wasn't as smooth as I would have liked. I also filled the cement board joints with "tape" and modified thinset (and covered the screw holes with thinset). Then I covered all seams and joints with KBRS gauging fabric, as per KBRS instructions. Finally, I coated the whole thing (walls and floors) with at least two coats of KBRS "liquid liner" (three coats on the corner & side joints).

    As for flexing, I'm concerned that because of temperature and material differences the sides and floor will expand and contract at slightly different rates. If I use something like grout, this might crack. A silicone caulk should absorb those slight changes without cracking... I think.

    Thanks!
     
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  4. gzecc

    gzecc
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    Caulk that matches the grout. Caulk should be used in the corners where walls and floors meet. Caulk will expand and contract with movement,, grout will not.
     
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  5. Wooden Head

    Wooden Head
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    I would not worry about the expansion between the two materials. I'll assume a couple of things.
    The cement board terminates inside of the shower base?
    If this is so, you can use a flexible sealant between the bottom edge of the cement and the shower base.
    I believe the color matching caulk suggested will do what you need. I you can, stay away from silicone caulk.
     
  6. TresK3

    TresK3
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    Jul 12, 2007
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    Thanks for the replies.

    The cement board landed on top of the shower base (there wasn't really a lip on the outside edge, just a flat spot). I used polyurethane caulk (supplied by KBRS) between the backer board and the base. I will definitely go with a caulk between the bottom of the wall tile and floor, and in the corners.

    Why do you say not to use silicone? What would you recommend? Polyurethane? That stuff was really difficult to work with.
     
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  7. Wooden Head

    Wooden Head
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    Sep 14, 2009
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    Silicone is not a great mastic. It will stick to some surfaces, but how well it adheres can be a problem. Wet silicone will not stick to dried silicone. This is a problem when trying to redo an area. Not very many things will stick to dried silicone.
     
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