lls8000 wrote:
I'm planning to tile a kitchen and dining room area, it's about 600
sq'. There is currently a 1/4" plywood underlayment over particle
board.

And what are those installed over? You don't give enough specifics to
warrant precise advivce. fwiw, neither of those are acceptable
substrates for ceramic tile.

What type of mortar and grout is best to lay over plywood?
I am not willing to replace the plywood with a cement board.
I've done multiple bathroom tile jobs, but this area is much larger,
I'm more concerned about the base.
Thanks, lls8000


I recommend you call a pro and get first hand advice and have them
perform the work.