I am going to be tiling 3 complete walls in my bathroom. The walls are currently tiled and have been painted with tile paint, which is in good condition. Is it imperative that the paint is removed or can I get away with scratching and coating with PVA mixed with sand. Alternatively, my last option would be remove all the tiles, however, I am dreading this as the walls are lathe and plaster, and therefore would probably crumble. Any advice would be appreciated.
Removing tiles would be your last option? It's always my first option! I remove tiles almost every week, and apart from 1 wall on a job about three weeks ago, I cannot remember the last time I tiled over tiles. Do this at your peril particularly over painted tiles! See
The plaster may be better than you think as the tiles may come off easily. If not it is a straightforward case to remove all plaster and screw / drywall plasterboard in place. Then tile the fresh surface. Maybe dusty, but it won't end in tears.