Want to change ceramic tile to granite tile

smart2surf

The underlayment is Durarock, on top of probably plywood floor 3/4", and possibly tongue in groove underneath. Ceramic tile has cracked from movement even though it does have Durarock as backerboard and I was planning to shore up the floor from underneath since there is a three foot crawl space under this wood frame house.
I am going to remove the broken ceramic tile and scrape off the white thinset bedding compound that is about 3/4" to 1" thick, and try not to damage the Durarock backerboard in the process.
Any suggestions as to how I could best go about doing this?
Since this is an older house that we have purchased, I don't know how the Durarock was installed. It may have been screwed to the plywood subfloor and 2x8s on 16" centers. There is a lot of flex in the floor in some areas.
Any suggestions as to how I could fix this problem. I wonder if I should put a layer of the pastic membrane Ditra over the Durarock.
It seems like the floor was not originally level, and the tile was installed by a do-it-yourselfer. Even though all the cuts seem to be centered in the room and were installed on a diagonal pattern.

Just Bill

It sounds like the floor is thick enough and it should be rigid enough for tile. What is the joist size, spacing?? Could be a problem with the thinset, too thick, not uniform, etc. You can get all the old off with a rotary hammer and a chisel blade.

JazMan

I doubt very much if the floor is built the way you think. There is no way the thinset can be 3/4-1" thick, I think you have a standard "mud-job". If this is the original floor I am positive!.

It sounds like you're gonna have to remove the entire thing down to the plywood and maybe further. Chances are the mud base is all cracked up.

If that's what you end up doing, get back with what you find in detail and how the framing is built, no words like "probably or possibly" please.

Jaz

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smart2surf

It is porcelain tile laid with 3/4" white thinset on durarock on plywood, and the 2x6 joists are 16 inches apart on a 12 foot span, with no center support. We know it is not the original flooring, it was our neighbor the do-it-yourselfer who installed this floor ten years ago, and he had no idea what a level was for.
My question is, how thick of a mud bedding would it take to set granite tile if the durarock is not damaged in the removal of the porcelain and the thinset.
Am I wasting my money buying granite tile, or should I find some alternative stone?