On 5/31/2013 12:34 AM, bob wrote:
I just had a brick fireplace tiled with marble tiles.

Should I seal it with natural stone sealers? Is there a chance water
would form behind the tiles and migrate into them from the back? The
fireplace feels colder than room temperature during the winter -- the
back side of the fireplace is the base of a chimney outside the house.

Three contractors came to bid on the job. None of them mention anything
about sealing the tiles. Perhaps tiles on fireplace don't need to be
sealed?

yes, if not simply for ease of cleaning soot off them.