Hello. I am trying to determine what type of fireplace I have (zero clearance or masonry). All evidence points to masonry, however, the face of the wall above the fireplace is drywall, not brick. Below the drywall is the mantle, and below the mantle is 12" tiles going around the fireplace opening. It is a gas fireplace. I see no metal whatsoever in the firebox. In fact, the grout around the brick is deteriorating in some places. If I stick my head up the fireplace, there looks to be a tile flu (square-10" by 10" or so, rounded at the corners). In the basement, there is block concrete below the fireplace (everywhere else it is poured concrete). There is also poured concrete directly under the hearth (as visible from the basement). I am trying to install glass doors purchased at Home Depot, however the lintel seems to be upside down, with the accessible part of the lintel hugging the tile surround; so there is nothing to screw the set screw into. I am stumped. I would appreciate any advice. Can I post pics on this website? FYI, the house was built in 1994.