We just did a complete (and expensive) remodel on the master bath, as well as a kitchen remodel. We have new flooring throughout the house and fresh paint on all the walls. So....I want to 'help' the full bath in the hallway. However, we have broken the bank already AND I do not want something that is going to mess up the entire house. So here is my thought: We have a tub that definitely needs to be re-glazed, and the walls around the tub are the usual 4" cermic tiles. The tiles are not in great shape now and the grout lines look awful. I want to know if, since the present tile should already have the necessary moisture barrier behind it to 'seal' the water out of the walls, etc...can I just put up hardy board over the tiled area according to directions (attaching to studs THRU the cermic tile) and caulking corners and area near tub rim...THEN after taping seams with fiberglass tape and doing the skim coating, can I put up a 12x12 ceramic tile? I HAVE done 12x12 ceramic tile on a vertical surface before, as I covered our huge but out-dated brick fireplace years ago and it still looks perfect....so I am not completely ignorant on that part of the plan. I realize that I will be actually bringing the wall 'in' the 1/2" depth of the hardy board and the depth of the tile. I don't see that as a problem, as I can choose an edge finish tile type that will work with the added thickness. I DO NOT want to take the present tile down because, of course, that was done in the master bath and I'm familiar with just what that means (gutting and a LOT of dirt and debris). I've read online about putting ceramic tile OVER ceramic tile and what is necessary in preparation...however, I was thinking that the perfectly flat surface of the hardy board would provide a better substrate to attach the 12x12 tiles. Yea or Nay folks??