Ceramic Tile Over Luan Plywood

I just finished prepping my 16 x 16 kitchen for ceramic tile.

Ceramic tile over luan plywood. Luan is a hardwood species containing extractives sugars. Never have that under tile. If you are looking for correct then the luan has to come up. I installed 3 4 plywood over the 5 8 underlayment.

Luan plywood is an unacceptable and unapproved substrate to receive tile or cementitious backer units cbu. Plywood in ceramic tile installations. Plywood underlayment is a thin plywood material that is most commonly used under resilient flooring materials such as vinyl and linoleum sheets and tiles. Wood based panels such as particle board composite panels veneer faces bonded to reconstituted wood cores luan plywood and soft wood plywood all expand and contract with changes in moisture content and are not recommended as backing materials for ceramic tile.

The books says a minimum of 3 8 underlayment grade plywood no 1 4 then use ditra or a 1 4 cement backer board both are installed in a wet bed of thinset. It can also be used under hardwood laminate and carpet but this is much less common these days because subflooring is typically smooth enough for these materials many of which are installed with a different type of underlayment or pad.