I would like to paint or tile a concrete floor now coated with polyurethane. How do I prepare the floor.

Question

If I have to remove the coating first, what is the best method?

Answer 1

If you are going to tile, you need do nothing, assuming you mean ceramic or porcelean tile put down with thin-set mortar.

If you are thinking painting, paint does indeed tend not to stick very well to poly.  It would be a big job, but surface sanding just to get the gloss off anything would very much help the paint to adhere.

Answer 2

All you need to do with concrete is prime.