Wet Room Shower Trays - Help Needed!

[Triassic]

I’m desperately trying to get the house finished for Christmas, mind you I said that last year!

 

I need to install a wet room shower tray into a quadrant shaped space. I intend to remove the existing 22mm chipboard floor. I’m told my options are to lower the floor to provide support for a foam core type tray or to go for a pre-cast try, which sits on the joists. One problem I’ve got is the position of the waste outlet, I need to position it  between the existing metal web joists.  The waste will be located around 150mm in from the bottom right corner edges.
 

I’ve looked on-line, but it’s not quite the same as seeing the product! How did you do yours and is there any particular product or approach you would recommend?

 

 

PS. Someone suggested I could lower the floor to provide support, then screed, with a fall to the waste kit? Has anyone tried this?

[Triassic]

Sorted!

 

After talking to various shower tray manufacturers about a custom fitted shower tray Ive decided that that having a bespoke  shower tray made is too expensive. I found a company called Jackoboard. U.K. do a rectangular wet room shower tray that can be cut to suit the shape of the space.