Tiling upstairs

"D'Olier" wrote in news:46b9198d$0$12243$ snipped-for-privacy@roadrunner.com:

Tile, a bathroom and an upstairs.

You dont have to use cement board (unless you have "Ducks" that throw water onto the floor) but you should have at least 1 1/4" thick plywood base to prevent flexing and cracking the grout. What do you end up with if you add

My floor guy used plenty of white woodworkers glue and a LOT of staples to attach the "extra" ply to the subfloor. Three years in, no flexing/no problems

If you do determine that you have flexing, and you cannot fully eliminate that flexing (for whatever reason). Then you should use smaller tiles on the floor like 6x6. The larger the tiles you use, the harder your subfloor needs to be. Women dont like to hear that because the big tiles have been in vogue for a while now, but maybe you can appease her by putting big tiles on the walls and small on the floor. If you can get a good solid floor then use thinset for setting the large floor tiles not mastic. Mastic or thinset is ok for the walls though.

There is a scientific way to determine whether the floor is strong enough, but 1 1/4" plywood and 1/4" backerboard is normal from what I've been reading. What is there now?

A change in elevation between rooms is pretty normal. We're used to picking up our feet as we walk through doorways. The bathrooms in my house are 3/4" higher than the hallways and I didn't even realize that until I retiled one of them.

So does the carpet rise up or do you see the edge of the plywood floor from the hallway?

Thanks.

You go to a flooring supply store (which has more choices than HD or Lowes) and get some " transition strip" so the answer to the above is "Neither"