I want to lay 16 x 16 3/8" porcelain tile in my bathroom. My subfloor is 1x6 T&G on the diagonal over 2x10 floor joists spaced 16" o.c.

The subfloor looks ok, but does have knot holes in it in some places and is nicked in others from removing old oak floor planks that were initally over it.

I'm trying to prep the floor and add tile, without raising the level of the floor too much (this floor is rising to meet rest of oak floor which is 3/4".

Here is my plan. I was going to screw down the subfloor for extra stability (put a few drywall (something else?)) screws in subfloor that is there then add 3/8 plyboard (maybe that 4x4 multiply stuff) and screw that down as well.

Then add Ditra, then my tile.

No matter what I do my tile will be higher than the rest of my flooring since I only have 3/4" to deal with, but I'm hoping to keep it as close as possible.

Will this work as far as support for my tile? BTW, I did use that "deflecto test" and my floor passed, for what that is worth.

Also, a follow up question, when applying the 3/8" on top of the subfloor, I keep reading conflicting advice as to whether to screw into both the subfloor and the joists or just into the subfloor and avoiding the joists...what do you advise?

Thanks so much!

Suzanne

3/8" will work, but 1/2" ply would be a little more stable if you could stand the extra 1/8" of height.

You don't want to use drywall screws in any part of your project. Use 2 1/2" deck screws to screw the 1x6's to the joists. To screw the plywood to the subfloor, you have two options: 1. use 1 1/4" deck screws, or 2. use longer screws but avoid screwing into the joists.

Use the following info for installing the plywood:

http://www.schluter.com/5138.aspx

Thanks for the info....much appreciated!