We just removed the old floor from our bathroom. My husband is going to put down 3/4" plywood and then 1/4" Hardibacker on top of that. Is it okay to use pre-mixed thinset mortar to set the Hardibacker on top of the plywood?

Also, do you use a square-notched 1/4" trowel to apply the thinset?

Thanks a bunch!

MarthaB

PS... I don't know if it matters, but we're going to put tile on top of the Hardibacker.

Thinset