I need advise on installing slate flooring in a bathroom (tiling, subfloor)

[lakerat]

I am attempting to remodel a small bathroom and wish to replace the cheap linoleum with slate tile on the floor. I just pulled up the linoleum and found that the previous owners of our house had put down, what appears to be 3/4" plywood on top of the subfloor. My understanding is that I need to put down cement board in order to lay the slate tile but that would raise the height of the floor way too high.

Should I pull up the plywood and replace it with 1/2 inch cement board and then lay the 5/16 inch thick slate tile?

One other thing. Right now the bathroom has a 4'x3' fiberglass shower stall that sits on top of the 3/4" plywood. Should I remove the shower stall and remove all of the plywood and then re-tile the entire floor, even under the shower stall?

Or, is there some other, thinner product available that I could lay over the plywood so as to not have to add the thickness of the cement board?

Thanks for any advice.

[K'ledgeBldr]

How do you know the 3/4 ply is not the subfloor?
If, in fact that is the scenario- pull the 3/4, inspect the existing, and if it is good (5/8" or better, little or no deflection, or rot, add the 1/2" cement board and go.
Leave the shower as is- don't make more work for yourself.

[lakerat]

Thanks for the reply. I don't believe the plywood is the subfloor because I have been in the crawl space under the house and see what appears to be 1x6s run diagonally on the floor joists. Also, the plywoof in the bathroom is the samd height as the hardwood flooring in the adjacent bedroom.

You are right. I don't want to make any more work for myself if I can help it but, how close to the edge of the bottom of the shower stall would I need to get to cut out the plywood? My circular saw can only get up to about one inch away. Is there a saw available that would cut right up to the edge?

If not, would it make sense to cut the plywood up to about one inch away form the bottom edge of the shower stall. Then put down a piece of 1/4 cement board on top of a piece of 1/2 inch cement board to bring the level up to the plywood or maybe a tad higher, and then just make sure I caulk that area real well?

Or is using 2 layers of cement board a no no?

[Ultrarunner]

You will need to know exactly how the existing floor was constructed.

I did a floor this weekend that had 1" T&G covered with 1920 Linoleum, covered with another Linoleum, covered by 3/8 Particle Board, covered with a inexpensive no wax vinyl... I picked up almost an inch by going back to the original subfloor.

It is very important for any type of slate, stone or tile to have a very solid base... the best is a "Mud" job where the slate is set in mortar.

All of the cement backer boards are good when going over something solid... anything else is just asking for trouble.

Determine the amount of space the finish floor needs and work backwards from there. Don't forget about extending the toilet flange.

[lakerat]

Thanks. It appears the plywood was placed over the bathroom subfloor to raise that floor level to match the 1 inch (actual thickness of 13/16) T&G in the adjacent bedroom.

So, if I understand correctly, it would be OK to remove the plywood up to within about one inch of the bottom of the shower stall, and then put down 1/4 on top of 1/2 wonderboard where the plywood had been. The actual thickness of the plywood is 11/16 so I'm guessing that to be 3/4 inch plywood?

Oh, and thanks for the reminder about raising the toilet flange.

[K'ledgeBldr]

Drill a hole through the floor (about 3/4- 1") and measure the overall thickness. If the 1X6 are true 1" thick and what ever the plywood is, sounds like a pretty stout floor. I'd go right on top of the existing and not worry with cement brd.
As Ultra said- a mud bed is best, especially if there is deflection in the floor. But then you're jacking the height of the floor up- and I guess you're trying to avoid that.

[lakerat]

You're right. The least work would mean going right over the existing floor. I read that in the case of kitchens and bathrooms, cement board is recommended but, if it is not necessary, then that would be the esiest.

Oh, total floor thickness is about 1 1/2 inch.

[rubytue]

Like Ultrarunner said, you need a very sold base to use real stone. Over on the John Bridge tile forums there is a "deflecto" tool, where you put in your joist information and it calculates if your construction can take ceramic tile or stone floor. Its very important you know if you have a strong enough base for stone.

We just did some tiling and used a new product from Schlueter instead of cement backer board. I think it was called Ditra. Good stuff! More expensive that cement board, but I feel more confident in the installation, too.

[jack_stoneworks-gallery]

lakerat,
Slate is one of the most beautiful natural stone tile on the market. However, setting slate isn't the easiest of tile to install because of the uneveness. Your situation isn't that uncommon, not only for slate ,but other natural stones as well. To address the variance, you might want to consider a product made by Schluter Systems called Ditra Mat([url=http://www.schluter.com/index.aspx]Homepage - Schluter-Systems[/url]). This product will not raise the height of your "new" floor" as high if you used backer board and it's more than adequate to support your installation as long as you follow mfg's instructions. In short, you'll demo the existing flooring down to your sub-floor, apply the Ditra Mat then you're ready to install the tile. One thing about slate is it's porosity. You will want to seal it prior to and again after grouting. Also remember to use a wet spongue when wiping the stone, careful to remove all of the grout from the crevices of the stone.
If you have questions further, feel free to email me.

[jack_stoneworks-gallery]

you can purchase Schluter at most high-end tile distributors like Specialty Tile, Zumpano Tile or Inter Ceramic Tile & Stone.