I am installing a very heavy stone resin shower tray Crosswater Linear 1500x800 in a u shaped 1500wide x800 deep space plasterboard walls in upstairs bathroom with P5 flooring.
Instructions insist on setting tray on mortar 5:1 ratio with a plasticiser my questions are:
1 )do I need any form of additional waterproofing
2 )how much plasticiser do I use in the mortar mix
3 )how much sand do I need for this area 10mm thick
4) plan to use my mate and glass suckers to lift onto mortar difficulty in u shape area is there a simple trick alternative