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.
Ceramic tile over luan plywood.
I installed 3 4 plywood over the 5 8 underlayment.
I just finished prepping my 16 x 16 kitchen for ceramic tile.
Luan plywood is an unacceptable and unapproved substrate to receive tile or cementitious backer units cbu.
Never have that under tile.
Luan is a hardwood species containing extractives sugars.
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.
Plywood in ceramic tile installations.
If you are looking for correct then the luan has to come up.
The seams between vinyl tiles allow water from spills or mopping to soak into the luan which can result in swollen plywood and lumps that are visible on the surface of the vinyl floor.