I am getting a subfloor and underlayment in a small bathroom replaced due to dryrot. The builder insists on 3/4 plywood (which is okay) and a 3/4 inch poured cement underlayment over it prior to my laying ceramic tile down (with thinset).

I noticed diagrams for a poured cement (versus screwed cement board) floor in the How To...Ceramic Tile section. It indicated that a 2 inch poured cement underlayment was appropriate. That is quite a difference. It also seems to me that 3/4 inch of poured cement would be more prone to cracking.

Am I overconcerned, or is a thicker cement base standard? The builder claims that his company will not use 1/2 cement board in place of poured cement by policy and may refuse to take the job. ?????? Should I be skeptical?

Thanks for any feedback.