There may be times when you want to bond tile directly to plywood, or another wood surface, rather than screwing down backerboard first. Backerboard can double the thickness of an installation, which can be troublesome in some locations. You may also want to tile an outdoor shed, or tile plywood boards for display. In any case, to bond tile to wood, you must use a flexible thin-set mortar with a latex additive. Wood shrinks and swells with humidity and frosts, which can break the bond between ordinary tile and thin-set. Latex will help that bond to last.
Things You'll Need
Latex thin-set mortar such as Super Flex or Laticrete Super Flexible Additive and thin-set
Find the ratio of water to dry mortar and reduce to the smallest amount you can use in 20 minutes. Thin-set dries quickly, and it must be wet when applied to bond properly.
Add the dry mortar to the bucket along with any liquid additives recommended by the manufacturer. Slowly add in the recommended amount of water, while mixing the thin-set with a trowel. Scrape down the sides of the bucket to ensure it is well mixed and stop adding water when the mixture falls off the trowel, but is not runny or soupy.
Spread a small amount of the latex thin-set on the wood with the trowel and rake it until the mortar is uniform in height and thickness. Install the tiles by pressing them into the thin-set and allowing it to dry for 24 hours.