Tiling across wall hung wc frame

[DIYMARK]

I have built a frame work to box in a Geberit frame and continue across the semi inset sink and end of shower. Frame is solid and I am intending to cover with water resistant plaster board.
Should I also cover with plywood?

 

[cam_low]

I do them with a ply inner skin then jackoboard or any other Tilebacker boards on top. 6mm or 10mm depending on your depth needs.

 

[beanz]

If there are enough noggins, and it feels solid, just the plasterboard. If there's flex, ply, then plasterboard. Don't tile on the ply.

 

[Chalker]

I always use a sheet of 12mm backer board where the frame is, it matches up to 12mm plasterboard either side. And give strength for the wc to be bolted back.

also run a bead od grip fill onto the frame to hep the backer board to adhere.