One more question as long as I'm talking with the pros. For the two layers of ACX 3/4" ply that I'm placing on the bathroom floor are ring shanks from a nail gun better or can I just stick with 3" 10 pennys?

Ring shanks are always better since they don't back out like 10 penny nails, however screws are even better since it will draw the subfloor down to the joists. You'll also want to use construction adhesive on each joist as you set the subfloor.

For the top layer, you should be screwing into the subfloor only, not the joists. This can be accomplished by using screws that are no longer than the thickness of the two layers combined, or by deliberately avoiding the joists.

Thanks for the info. With 2 layers of 3/4" ply, 1/2" layer of durock, then thinset and tile I know the floor will be more than sturdy. I have placed the plywood as per your instructions, laid over 16" OC floor joists with blocking every 2'. I can tell this things going to be a tank. I want the guy who has to demo it in 50 years to curse my name.

And yes I went with screws and adhesive as well.

Why not set directly on the plywood with a modified thinset? 2 layers of 3/4 is plenty strong enough. the durock is not needed unless you are trying to come up in height.

Because we want Kdog to do a real good job.

Two layer of 3/4" subfloor is a bit overkill, but the concrete backer or matting is the set the tiles on a "tile friendly" surface. Plywood is NOT tile friendly.

Kdog could have chosen a membrane which are from about 1/16" to 1/8" thick. Or 1/4" concrete backer instead of 1/2".

Jaz

Awesome, all this good advice and yes you guys are right I am trying to come up in height. With the 1/2" durock, thinset (before and after the rock) and then the thickness of tile I come exactly level with the wood floor in the hallway. I do have another question. I am putting down a building felt slip sheet in the shower area, should I just continue up the walls with it on top of the studs and behind the durock in the whole shower area? Or just do the pan that way? Thanks again, everyone on this site has been very helpful.

Your moisture barrier should be stapled to the studs and drape over inside the pan.