In some cases it is possible to install embedded electric floor heating over existing tile floor. You will need to check with your flooring manufacturer to see what requirements they have for the subfloor. Once you have that information, we can make a recommendation on whether floor heating will work for your project. A specific type of thinset may be needed for this application. In most cases you will need to repair or replace damaged existing tiles. They should then be scuffed or sanded, and then cleaned. After these steps have been completed, the new tile could be installed using the appropriate thinset.