Re: Cross plank sub floor for tile?
Another suggestion would be to use 5/8 exterior plywood with the rough side up.
Use construction adhesive to adhere down to the sub floor along with 3 inch screws into the joists .... 2 inch screws in the field to clamp the plywood down while the adhesive cures.
Then use the uncoupling membrane like the Schluter Ditra
or like this membrane by Superseal
These would get set in mortor on top of the rough surface of the plywood. The reason for the rough side up is to provide some texture for the mortar to grab.
The membrane will work to help prevent any cracks happening .
This will also save the 1/2 inch the backer board would have added.
Hope this helps.
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