Shower tray base, marine ply or wpb

[Moneypit42]

I’m fitting a 1200x800 quadrant shower tray & find marine ply a bit pricey, especially as I only want 1300mmx800mm so would be left with the rest of the sheet. It’s been suggested that WPB or softwood ply with a double DPM covering would be ok. It would of course have the standard mortar covering.
I’d like to save money but not at the expense of potential future problems. Any advice would be much appreciated.
Many thanks all you lovely people.

 

[gregers]

ive used wpb in the past without any problems.
i personally wouldnt be wrapping anything with plastic,it might make it sweat and that isnt good.