Our tub/hand held shower surround currently has green board (mold & waterproofed board) on the walls and is primed and painted. We are wanting to tile the walls, do we need to rip out the current green board and put up cement backerboard or can we put it right over the current green board?
NAN

If you leave tile over the greenboard and it gets wet... the tiles will fail
What was there before?is this a new install?

We are wondering if we can put up cement backer board over the current sheet rock and then tile. It is unfinished new construction.