On the floor is 1/2" hardiebacker for the tile with another layer of 1/2" plywood under that. The first layer is sika'd and screwed down with self tapping screws. The hardiebacker gets a layer of mortar (thin set) then it gets screwed down with 1 1/4" hardiebacker screws. When the tile goes down it is with a thin set mortar adhesive then grouted!