Satisfying the first concern is a matter of ordering a mantel that is sized correctly for your fireplace. The National Fire Code says that all combustible material must be 1 inch away from the firebox opening for every 1/8 inch it protrudes from the surface, with a minimum 6-inch clearance all around. (If stricter local codes exist, these supersede national codes). If you have an odd-size firebox, a stock mantel may create a disproportionate-looking reveal around the opening, so you may have to custom order to get the mantel to look right.
Satisfying the second concern is all about good carpentry. Many mantel-kit companies suggest merely toenailing the piece through the shelf directly to the wall, or even gluing it with silicone caulk. Since neither option is very sturdy, we recommend you attach the mantel to a cleat—a simple piece of lumber securely fastened to the wall. One cleat runs horizontally under the mantel shelf, and the others run vertically inside the legs (most mantels are hollow in back). Then you screw the mantel to the cleats along the back of the mantel shelf and the sides of the legs.
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Hammer drill with 3/16-inch masonry bit
to cut 2v4s
Comes in a kit with legs, a shelf, and interior trim.
to level the mantel.
3. 2x4 LUMBER
for cleats on which the mantel will hang. Two 8-foot pieces should do it.
4. 2 1/2-INCH-LONG 1/4-INCH CONCRETE SCREWS
for attaching the mantel to a brick chimney. If the wall isn't brick, use 3-inch decking screws to attach the cleats to the studs.
5. 2-INCH FINISH SCERWS
to fasten the mantel to the cleats. Finish screws (aka trim heads) have small heads that sink below the surface without the need to drill a countersink hole first.
6. 4d FINISH NAILS
to attach the edge molding.
7. WOOD PUTTY
to fill screw holes.
if you're painting the mantel, to fill gaps where it meets the wall.