On Mar 5, 2:06 pm, wrote:
So I talked to him, he said he'll use 1/4 hardy board. He said it's
like a cement board but the particles are finer. I asked him if he can
do 1/2 hardy (or cement) board and he insist those are used on walls
and not on floors.

Yes. According to the instructions, 1/4 is stronger than 1/2.


He did not talk about a layer of plywood under the bardy board, and I
didn't ask him either since I am just reading this now. Is a 1/4"
hardyboard enough? How important is the plywood layer? He said there
will be another layer of cement (thinset) on top of the board so
having a 1/2" cement board is too tall.

The subfloor is the most important part of the job. The tiles will
crack if it's not right.

Like Mike said, 1 1/4" solid wood with any layers glued and screwed
together. Thinset and nails/screws securing the 1/4" hardiebacker.
And that's a minimum if the joists are solid.

And yes, all that makes for a high floor when all is done. There are
ways to deal with the transitions.