We are planning to put ceramic tile in our bathroom. Do I need to put down thinset underneath the hardibacker (subfloor is pressboard) or can I just screw the hardiback down.
Thanks!

farmboy

hardibacker recommends thinset under the hardibacker, then screw it down. you can double-check this at their website... there is an installation manual there. that is the way i have installed it before... per their instructions.

hue

Backer board is somewhat brittle and does not have any flex.

The purpose of the thinset is give it a 100% solid contact to support it.

It is not for adhesive. The screws/nails do that job.