Hello, I have purchased some 12mm WBP ply to screw down on chipboard bathroom floor before laying 10mm porcelain tiles. However, following some research on the views of some on this forum I note that ply is not the best substrate for tiles. Can I screw the ply down then lay 6mm Hardiebacker on top of it. I realise that this would be raising the floor level which will mean shaving the top and bottom off the door and getting a longer soil pipe. If thats the way to do it. Please forgive the questions if it seems obvious to you guys but the fitter who started the job has left me in the lurch because hes got too much work on and in his words 'had to cancel a few jobs'. Thank you for any help you can offer.