Please briefly explain why you feel this question should be reported.
I have seen your videos on how to install a ceramic tile floor. I will start by saying thanks for making them, they were very informative about the process.
My question is about surface preparation. I have seen other videos or articles that claim laying new plywood or using cement board is a must, even some claiming both are needed to keep movement to a minimum. I noticed in your video that you just make sure the existing sub floor was secured well and tiled directly on top.
In what instances, if any, are the extra layer of plywood and/or cement board needed?
Thanks in advance for any advice!