Shower traps in screed floors

[vfrdave]

Doing the floor insulation in the house currently.  What should I do for the shower and bath traps.  Screed is a flow screed so nominally 50mm deep, traps are deeper than that.

[Temp]

Our showers are on first floor which is beam and block, insulation and ufh in screed....

 

We omitted the insulation and screed under the shower trays. Instead we built a platform from timber and WBP plywood to support the tray at the right height and provide a void for the trap and waste pipe. Used a top access trap positioned in a clearance hole in the plywood. Tray then lowered onto mastic on the plywood.Top of trap fitted through hole in tray into the lower part of trap.

 

This allows top of shower tray to be say 5mm above the finished floor level so the door seal doesn't scrape on the tiles.