Tiling over bathroom tile floor - pics included

[dfulmer]

Hi. My name is David and this site is fantastic! I got a lot of help on it in 2004 for my first tiling project, which was tiling over my 1970's brick fireplace and wall-to-wall hearth. It came out better than I could ever have imagined!

I'm now about to remodel my small (5' x 8') hall bathroom and I need help again. I need to know whether I can (or should) tile over my tiled floor in my bathroom. I've included pictures. The floor is now covered with 1/4" thick ceramic tile. I'm going to use 3/8" thick porcelain tile in my bathroom now. The tile on the floor is solidly attached and has no cracks. The subfloor is 5/8" thick plywood. There is a mud bed that appears to be 7/8" thick. There are a couple of squeaks when I walk on the floor (no noticeable bounce though).

Can I tile over the existing tile? If I can, do I roughen up the tile (how?), apply modified thinset, and then tile? If I shouldn't tile over the floor, will the mud bed underneath get ruined when I remove the already attached tile or do I have to remove the mud bed as well and add more plywood (how thick?) and cement board (how thick?) on top? I already own a rotary hammer and a flat chisel for it, if that will make the removal not a big deal.

How should I handle the transition to the marble threshold? The existing marble threshold is 3/4" thick. The new tile placed on top of the existing tile is flush with the top of the existing marble threshold. How thick will the new thinset add to the height?

Thanks for reading through all my rambling! I think I have a better handle on replacing the existing tiled tub surround than what to do with the floor!

[muskymike]

Hi David, welcome back! This would be about the only time I would say tile over the old tile. If you leave a grout line at the marble you will be fine with the height. Use a very good modified thinset for this. Like TECs Super Flex.

[Trask]

Yep, Mike 's plan sounds good to me. I'd make sure the existing tile is stripped of oils soap ect. TSP works good and it's cheap. I like to scatch up the surface real good with a carbide scribe. If time isnt a factor I like to flat trowel the floor with thinset, (in this case super flex or full flex would work great), and let it dry overnight. This gives me a nice surface to work on, draw lines on ect. Plus I feel like i get a real tight burn or bond into the old floor.

[dfulmer]

Thanks for your answers! From knowledge comes confidence!

I have another question: When I go to thinset border tiles onto the bottom of the new drywall (actually greenboard) in my bathroom where the walls meet the floor in the non-wet areas (as a substitute for baseboard), do I have to prime the drywall first, or do I just thinset the border tiles onto un-primed drywall?

Thanks!

[Theoderik]

no priming necessary. just stick them on

[dfulmer]

I laid out two designs for the two side walls of my tub/shower surround. I need to know which design is better.

I'm using 6-3/8" square porcelain tiles that are 3/8" thick. I have bullnose tiles also 3/8" thick that are approximately 3" x 13" that match the field tiles. With 3/16" wide grout lines, each bullnose tile spans two field tiles.

The first design aligns the edge of the field tiles with the front edge of the tub, with the bullnose tiles running down to the floor right along the tub. (I'll make a 45 degree on the bullnose tiles where appropriate; the sketch doesn't show these miters.)

The second design starts the edge of the field tiles farther out from the front edge of the tub so that the center of the tub is centered with the middle column of field tiles. But I don't like the two small field tiles in front of the tub.

Which design should I go with? The tiles are beige (they look like limestone), and I'm planning to use either a white or beige grout color.

Thanks!! I'm obsessing days over these little details!!