How do you tile over existing tiles? any tradesman?

Done this many times. As long as your base tile is down tight and CLEAN and dry. You do need a good thin set mortar. And I mean good..You don t need to sand the top of tile or screed a top coat. The one main trick nobody seems to do that I always insist on when I do the job is that there will bo no traffic on the tile for a minimum of 2 days. So easy to shear the bond on thin set going over tile since it take a longer time for thin set to dry under these conditions. Any questions you can e mail me GL