what did you use for the tile base - cement board?

The floor is done with wire lath and a mixture of sand mix and multipurpose, after that dried up, in went the heated flooring mat (nu-heat). The tub deck is all plywood, I couldn't argue with the Super/Carpenter, however, the top of the deck, was not level, so I plumbed/leveled it up, using a worn down quarter inch notch, to start with, then fine tuned it from there, using multipurpose and fast set, now the top of the Whirlpool deck is cement board. This area is not considered a wet area, and not absolutely necessary that we use cement board, but everything is installed with cement/multipurpose, should outlive us. I hope that answered your question mdog.

Yes, thanx! I had to replace cement board on top of my tub deck; went with hardiboard.