There are two materials commonly used for laying ceramic on plywood or osb that are applied before the tile.
How to tile over plywood subfloor.
The old fashioned mud method of floating a thick mortar bed in preparation for the tile has given way to using cement backer board over a plywood subfloor.
Once the surface is completely covered cover the adhesive with the fiberglass based paper and smooth out any wrinkles or bubbles with a broad drywall knife.
While tile can be laid on plywood do not install tile directly onto the plywood subfloor itself.
The plywood will expand and contract at a different rate as the tile causing cracks to develop in the grout lines or tiles over time.
It should be fastened to the subfloor using thinset and then screwed down every 10 square.
Concrete board concrete board also called backer boardcomes in 1 4 and 1 2 thicknesses and is usually sold in 4 x 6 sheets.
Use thinset with a higher latex content thinset is the wet base that you first trowel on the plywood to make the tile stick.
Use intervening layers of two sheets of plywood.
No matter how firm the subfloor.
For this project we are using the tavy thin skin system to prepare the surface for tile.