I'm fixing up a rental unit in an old house (circa 1890), and removed some ugly wood paneling around the fire place. Underneath is crumbling plaster, and under that is brick. Is there any reason I can't remove the plaster and leave the brick exposed? There is a small gap between the brick and the mantel, what would I use to fill this gap in? Also, at least one of the bricks that has been exposed to date has a large chip in it. Can this be filled in with something? Thanks.