Installing tile on Plywood

Jefftiles

I am in the middle of a project to tile my kitchen. I have removed the vinyl flooring and sanded the plywood so that it is perfectly level. My plan is to lay down the tile on the plywood given what I found.... when I looked at the flooring already laid down there is 3/4" plywood on the joist, cement board on top of that, and 1/2" plywood on top of that. I know that I need to protect against deflection, but how much more support is another layer going to add to my project.

Isn't there already enough down to prevent deflection? Or is there another concern that I am not considering?

More information:

the house was built in the mid 90's.
Ceramic tiles

oh'mike

Yikes--sounds like a concrete sandwich---

My question to you is --Do you want to do this floor right? Or just do it and see what happens?

Right would be to peal off the top two layers--leaving only the 3/4 sub floor-

add 1/2 inch ply on that--for a total of 1 1/4 " ply--then 1/4 inch cement board then tile.

I think the house was being prepped for tile(the cement board) and the buyer changed the plan to sheet goods.

Tile directly over plywood of any kind is a poor installation--wood moves-tile doesn't. If wood get wet it swells--tile doesn't do well if the surface is swollen.

----Mike---

ClumsyCarpenter

Don't know if it matters, but are you on a slab or do you have a crawl space/basement?