i was watching episode 3210. They were tiling a wall. The primary wall tile was a 8x24 ceramic tile and the accent tile was a glass mosaic. The two kinds of tile had a different thickness. So, they attached an additional layer of backer board where the accent tile would be going. This would result in the in the face of the tiles being flush once installed on the wall.
once backer board is installed the seams have joint tape applied to keep the grout from cracking. I would think having a step in the backer board resulting from adding an additional layer such as they did in the episode would result in a seam that would cause cracking in the grout.
So my question is whether anything special is preformed with the thinset or grout or anything else when this situation is encountered? And what would be done if the situation was a seam where backer board of different thickness meet?