Renewing Bathroom Floor

[dick290647]

I am renovating my bathroom (completely) the house is a 1930’s end of terrace. The bathroom floor boards are a bit rough and like a patchwork quilt so I am considering removing them and replacing with sections of WPB (Waterproof Ply) 18mm thick. looking around there appears to be several kinds my thinking is that the more plys the better is the quality and strength but I would welcome some advice.

I’m not tiling the floor but considering using Amtico floor covering and considered that using ply instead of new boards to minimise the number of joints!

18mm is near to the thickness of the existing boards and some of the ones around the room edges are under the walls and not removable.