New Floor Height question
I'm installing a ceramic tile floor in my second floor bathroom. The existing floor is 40 year old sheet vinyl, smooth and solid and fairly level. My question is how high will my floor rise if I first install thinset over the vinyl, then 1/4" Wonderboard, then thinset, then 5/16" floor tile? Does each layer of thinset add 1/4" of height? I'd like to install 1/2" backerboard because of its stiffness, but I don't want the floor to get too high.
By the way, I'm going to use cement backerboard for a wall that will only be partially tiled. Am I right to assume I can prime and paint this backerboard too?