I recently finished attaching CBU sheets as a base for tiles to 2x framing covered with 6mil plastic in our basement shower – both walls and ceiling. I realized after I’d done this (doh!) that due to heating ducts running inches from the shower enclosure along the top of one wall and along the middle of the ceiling that these areas would be subject to much different expansion and contraction than other areas, posing a risk of tiles cracking/heaving.
I therefore decided to not install tile near the top of the walls and the ceiling. Which brings up a couple of questions.
What do I coat the CBU with to get a smooth surface (it is a slightly glossy product with bumps and holes called Panaroc)? Would any of these coats be waterproof? Could the coat be painted – if so what kind of paint to use? Should the paint then be sealed somehow or would it function as waterproofing in and of itself?
Thanks,
TTL
Replies
Go to a masonry supplier or DalTile and ask for a trowel on membrane for waterproofing CBU's. They are a two part product of a thick black latex which is rolled or troweled on, then fiberglass mesh is embedded into the latex, then more latex is topped onto the whole mess. It cures overnight and is ready to tile the next day. The average shower takes about 3 gals, but at about $50 a gal., it is not cheap.
Laticrete 9235 is one such product although there are others, and there is not much difference in my opinion.
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927
Maybe I didn't make it clear in my original post. I do NOT want to tile some areas of the CBU. What I'm concerned about is how to smooth out and waterproof the parts of the CBU that will NOT be covered with tile.
Thanks,
TTL
I know of no product that will waterproof CBU's other than the trowel on membranes, which are black. I suppose you could use a wide flat trowel and use a tile patching compound like Custom's QuickFix or Mapei's Planipatch, then roll several coats of the membrane over it.
I do not know if paint would adhere to the membrane. I would ask the manufacturer.
I would just tile it. I guess I don't understand the reluctance to do so. Stupid white tiles would be way cheap.
Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1927