Two half-inch layers of exterior grade plywood undeneath Ditra seems plenty for a bathroom vanity with granite tiles - and what I remember doing. We used Rondec-STEP for the trim and it all fit together nicely.
I don't know about cbu...doesn't seems to add much, IMO. No water management, no structural support...Hmmmm; perhaps for ceramics but I'd still prefer more support for stone.
Floor is done, now for the vanity.
1). What spacing do you recommend on 12" x 12" granite?
Size is about 62" x 22".
2). Also, I need to cut two holes in the granite, one for the drain (Vessel sink), and one for the faucet (tall single type). Any suggestions on that? Do they sell a hole saw for that? Diamond blade I guess?
I just did a granite kitchen counter top and I used 2 layers of 3/4" ply and then ditra. It was my first time using ditra and it is really nice stuff and easy to work with. Also it gives you the waterproofing you should have on a countertop. It wasn't that much more than CBU and I think it is worth it. I used 1/16" spacers for the tiles. It gives it more of a solid look. Make sure you look into sealing the granite cause I read some granites will get stains from water spots and other things.
For the holes I would invest in hole saws, they are a little expensive but will give the best results. Just do a search online for diamond hole saws. Another option would be to call some local tile installers or suppliers and ask if they can drill the holes for you for a small fee. If you mark the tiles and bring the tiles to them they might do it for you for a couple bucks.
If you do end up using ditra you use modified thinset between the ditra and ply and then un modified between the ditra and granite.
Thanks for the tips. I just used Ditra on the floor so yes it is easier. 1/16" spacers is what I bought, so I was correct on that.
On another note, I have the pieces that go around the edges of the vanity for the finished look. Problem I see is my vanity top is only going to be 21" deep with tile and if I wanted the tiles spaced from the wall to the front evenly, grout line down the center lengthwise, I would need to cut both the back and the front since the tiles are 12" each. Doesn't look like that will be an edge for grout at the front with those pieces. Or do I use a full tile along the front and have my grout line off center lenghtwise.
You can do it either way. It depends on the granite you have. Does the granite have a smooth square edge from the factory? If you are using a tile saw and can get a nice edge that matches the factory edge you could cut your front tiles so that the grout line is centered. I don't think cutting 3 inches off the back tiles would look that bad but guess it depends on how your tiles look. Guess I would cut a tile to center the grout line and see how that looks, if you don't like how that looks you can put a full one in front and then re-cut the tile to fit in the back row with out wasting any tiles.
Also remember that with 1/16" grout lines you need to use unsanded grout.
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