I want to install Kohler Choreograph sheets in my shower over tub. It currently has a full fiberglass unit. Should I use osb, greenboard, or possibly cement board, and do these have to be water-proofed?
According to this video produced by Kohler, you should use greenboard or other water resistent backer material. I wouldn't use OSB, and cement board seems like overkill but could help if you needed to stiffen up the walls I guess.
Kohler recommends water resistant drywall or green board. Make sure you have blocking at the height needed if installing things like hand rails.