Help with tiling over tile in my bathroom [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile

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Seth M
03-31-2011, 07:27 PM
I'm a first time tiler with some questions about laying tile over a tile bathroom floor. It's a small bathroom approx 30sq ft of 4x4 white tile, ceramic I think. I was going to rip the old tile up and start from scratch but it's laid in a thick bed of mud and since the old tile is rock solid I'm just going to use it as the subfloor.
Questions:
1. Do I need to roughen the surface of the old tile? I've read a belt or oscillating sander with a silicon carbide medium would work. Is this true and necessary?
2. Should I place a waterproof membrane between the old and new tiles? If so is a liquid or rollout under-lament preferred? Specific brands would helpful.
3. What type of thinset? Does this depend on if a waterproof membrane is necessary? I'll be shopping at HD or Lowes so any brands you recommend that I can find easily would be a big help.

Thanks for the help, I can provide more info if necessary.

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Davy
03-31-2011, 07:41 PM
Hi Seth, welcome. You can tile right over it without a membrane if there aren't any cracks in the floor. Rough up the glaze any way you can. I would probably use a grinder with a 4 inch diamond blade or cup wheel but a belt sander may work fine. Scatch it up well and use a good thinset, something like Flexbond from Home Depot.

Seth M
04-01-2011, 06:17 PM
Thanks Davy. Glad to hear that I can save a step and skip the membrane. When roughening up the tile I just need to take a thin layer, right? Just enough to take the glaze off and bring it down to a porous surface??

Seth M
04-02-2011, 09:46 AM
Also, what size notched trowel will I need to lay the new tile? It's a 12x12 travertine mosaic (9 pieces of approx 4" per piece on each tile minus the 1/8" joints)

Jaz
04-02-2011, 10:00 AM
Hi,

Since your travertine mosaics are probably a full 1 cm in thickness, (right?) a standard 1/4" square will be fine.

Jaz

Seth M
04-02-2011, 07:43 PM
Thanks your right, the tiles are about 3/8" or right around a cm. I appreciate the help.