Subfloor Support

[Sabrexr15]

Hello All,
I am planning on installing this tile in a bathroom floor, 8'x10'
what all do I need on top of the 3/4" plywood subfloor?
Various tiles, 24x24 12x24 12x12
Planning on using a Strata mat or Ditra, haven't decided yet.

[cx]

Welcome, Barry.

First you need to evaluate your joist structure to determine if it is suitable for a natural stone installation without some improvement. Hint: It's not.

Then you must install a minimum of nominal half-inch exterior glue plywood with no face of grade lower than C on top of your existing subfloor. Then your tile substrate of choice.

My opinion; worth price charged.

[Sabrexr15]

Thank CX,
I have 2x10 joist 16" OC
wasn't sure if I needed the 1/2" plywood or cement board or hardy backer.
If I use the 1/2" plywood, would using wood glue and screws give the best strength when attaching it to the subfloor?
There's also a 1/4 plywood on it now on top of the 3/4" plywood

[cx]

Doesn't tell us much without we know the species and grade of the joists as well as the unsupported span, Barry. You may have difficulty with the first two, but you absolutely must know the unsupported span.

Properly gluing the second layer to the first would provide the maximum stiffness, but I would not recommend you do that. Here is a good article from our Liberry showing what I've come to accept as the very best way to install that second layer.

The quarter-inch plywood must be removed.

My opinion; worth price charged.

[Sabrexr15]

Outstanding article!
Thanks for the solid advice.

[Sabrexr15]

One other question, I just built an outside deck and applied screws to the plank boards. Can I use those same screws for the 1/2" plywood on top of the subfloor?

[cx]

I dunno. How many pancakes does it take to cover a dog house?

Maybe you could tell us about these screws?

You require a coated or treated screw with a flat head that's long enough to fully penetrate the first layer of subflooring.