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

[boat21]

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?

[jadnashua]

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.

[johnfrwhipple]

What type of waterproofing do you plan on for the floor?

Is there any deflection in the wall assembly right now?

You might consider installing 1/4" hardiboard or 1/4" green Eboard over the exsiting drywall with a thin set application. I would leave the bottom 6"-8" untouched to allow a liner to run up the wall and allow room for folded corners. After this assembly is floor tested I would tape these seems and scratch coat it with a good thinset.

The corners could be folded into the two short walls as well and this step could be done there instead.

These measures all to save a little work and leave drywall in your shower. It can be done but why no rip out the drywall and attach new concrete board to the cinder wall with thinset?

By ordering 4-5 sheets of 1/2" concrete board and 1 sheet of 1/4" you can build a bullet proof shower and have no drywall in the wetzone.

JW

[geniescience]

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.


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John's first two questions are OK. Answers those questions.
These other ideas from John are dumb:

... consider installing 1/4" hardiboard or 1/4" green Eboard over the exsiting drywall with a thin set application. .... why no rip out the drywall and attach new concrete board to the cinder wall with thinset? ...

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.