Hi Guys, I need help!! Basically I employed a cowboy and now there is a problem I can't contact him! I had my floor tiled (over 200sqm) prior to turning the under floor heating on. Now the heating has been on and off for over a month the tiles sound hollow when I walk over them! I feel they will crack in time and I haven't moved in yet so need a quick solution!! Will i need to take all the tiles up? It's not all of them just 3/4. Thanks in advance.