We had gas logs installed in our fireplace last night. The installer said that we should burn it for a couple of hours to get the logs set. Ok, it was cool so the fire was nice. When I went to bed I shut the fire off but when the fireplace cooled the bottom row of tile across the fireplace popped off. Anyway, looking at the construction, the builder tried to stick the tile to the metal fireplace with thinset. Obviously the difference in expansion between metal and tile makes thinset a bad choice. Ideas?