Hi All, I need some advice on how to fit a shower tray. I have a 760 x 760 mm, stone resin (ABS capped), low profile tray. It has been raised for access and drainage on wooden structure of 3x2 wood with 18mm ply overboard. The wooden structure is flat and secure, however my builder wants to just float the tray on top of the ply (not stuck to the ply with anything) but I think it needs to be bedded in on a 5:1 sand / cement mix. I have trawled through various forums and spoken to a few plumbers but no one can give a definitive answer. Any comments would be helpful as it is planned to be fitted tomorrow.