So I've decided to finally rip up my 3 year old lino in the upstairs bathroom and lay some lovely looking wood effect porcelain tiles down. I have some experience with past tiling jobs but these were on a concrete floor. Bathroom setup Just over 4m2 area with 25mm wood ply/chipboard flooring from original build. I have already cut out 6mm hardibacker which sits nicely on the existing wood floor (loose) Plan is to lay 150x600mm porcelian tiles. Questions Is it better to lay the hardibacker in a thinset of tile adhesive as well as screw down? If so would a standard mapei bag be ok for both hardi and tile application? Looking at this http://www.screwfix.com/p/mapei-floor-wall-tile-adhesive-grey-20kg/4367d I would use flexi grout but not sure if I need to use flexi on above also? Is it ok to screw hardi into floor with 20mm screws as I am concerned any further will hit a pipe somewhere (already done). Any advice on the above much appreciated. As learned from previous jobs its all about that prep work!