tilling onto wood in shower room

[captain chaos]

hi, im looking to put right a mistake that was made previously in a shower room. i have a 1400 shower tray in a room that is 1480 wide, so at the end of the shower there was a gap that had been filled in with ply and then tiled over, this failed and i have taken the tiles off. my question is how should i prepare the ply to re cover? the shower tray can not be moved, its fitted well and tiled all round and i cant build a false wall at the end of the tray as to do so i would have to re tile the entire room as the tiles are no longer available. at the moment the two options sem to be to treat the wood with something that will be completely water proof and then re tile, or to cover with 95mm upvc architrave, but once again what to protect the wood with. any help and advice would be welcome

 

[EalingBadger]

uPVC is the way to go.

Wood will be very difficult to waterproof effectively. Over time it will move as it absorbs moisture and then cracks will develop.