avoiding hanging concrete board and waterproofing a regular wall for a shower instead

Discussion in 'Shower & Bathtub Forum & Blog' started by boat21, Mar 8, 2011.

  1. boat21

    boat21 New Member

    Mar 8, 2011
    Ottawa, ON Canada
    I am in the process of building a tile shower from scratch. I planning to build the base myself out of tile and I have researched how to do it and make it water tight. When completed, the shower will be about 32X 48. The shower will open on one of the 32" sides. I plan to use concrete board on the other 32" side and one of the 48" sides. On the second 48" side, I would like to know if there is a way I can use the existing wall (it is an external wall of the house made of cinder blocks, with some mortar on top of the cinderblacks to smooth them out on the inside and then with either finish plaster or maybe some old version of drywall over the mortar. (bear with me, it's an old house) I am concerned that if I take it down to the cinderblock and attempt to hang concrete board, that I will have nothing onto which to screw the concrete board (drywall or plaster is probably hung on wood pieces nailed into cinder blocks but might not be strong enough to hang concrete board )so I would rather not fix it since it aint broke and add a membrane or tar paper (?)or coating to the existing wall and then tile over that. Space is really tight so I dont want to build a fake wall just to hang concrete board. Can I do this and if so what should I use?
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Sep 2, 2004
    Retired Systems engineer for defense industry.
    New England
    You could use a paint-on surface waterproofer such as RedGard, or a surface membrane such as Kerdi, or Hydroban, but then you'd need to cover it with tile. How are your going to hide the pan liner if you don't put something up on the concrete block wall? You need your waterproof layer to be sloped, and that isn't the tile...it's some kind of membrane. Kerdi or Hydroban could be applied directly to all of the walls, and could also become your liner, then tiled. If you use Kerdi, you can build your other walls out of regular drywall, since the membrane is totally waterproof.
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  4. johnfrwhipple

    johnfrwhipple BATHROOM DESIGN & BUILD for both Canada & the US

    Jul 20, 2009
    Design Work World Wide: Bathrooms Vancouver Area
    North Vancouver, BC
    post(s) deleted by John Whipple
    Last edited: Mar 17, 2014
  5. geniescience

    geniescience Homeowner

    Nov 27, 2005
    humid summers hot, humid winters cold
    Cold country is where you are. Use ANY foam board. Search for Wedi. They are in Ontario. Search for Schluter. They make Kerdi-Board and they give free courses within 2 hours' drive of Ottawa.

    The reason to use foam is for Insulation. You are in Cold country. "An external wall of the house made of cinder blocks, with some mortar on top of the cinderblacks to smooth them out on the inside and then .... (bear with me, it's an old house) ..." This doesn't sound like a warm old house.

    You can "take it down to the cinderblock" and you do NOT need to hang concrete board, although you could do it very easily with the right screws and an electric drill. But don't.

    The foam board IS a membrane. You seal the panel seams with SikaFlex or some such. (Wedi or Schluter will tell you what to use.) Then tile over that.


    John's first two questions are OK. Answers those questions.
    These other ideas from John are dumb:
    John's a good guy but he's doesn't always sing on key.

    Do not let anyone convince you to put concrete board on an uninsulated exterior wall. Use foam board.

    In the other areas, use a liquid membrane. Two product names have been given above. There are others. They are all good. Read instructions, and post again.
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