How to Add a Mantel to a Brick Fireplace

Measure your fireplace. Purchase a mantel with an inside frame that has a top horizontal, or mantel shelf, at least 10 inches above the top of the firebox, which is the rectangular inset where the fire actually burns. The side columns need to extend at least six inches from the fire box on either side. Check the prefab mantel's installation specifications to ensure you purchase a mantel that has hollows behind the side columns and mantel shelf to fit over your installation cleats as outlined in the following steps.

Measure the inside hollows on the back side of each column and the mantel shelf. Cut three ¾ inch plywood pieces to use as mounting cleats (one to fit inside each side column and one to fit inside the mantel shelf) with a circular saw. Dry fit (or check the fit of the cleats) by setting them into the back of the mantel. Make any adjustments needed for a snug fit.

Set the mantel with the bases of the columns on the hearth and the back of the mantel flat against the fireplace face, centered on the firebox. Mark the outline of the inside rectangle of the mantel on the brick lightly. Mark the positions of the hollows from the back of the two side columns and the back of the mantel shelf onto the fireplace face in relation to the inside frame outline you drew. This will indicate where to install your plywood cleats.

Drill pilot holes in the plywood cleats. Clamp the cleats to a sturdy surface with a C clamp so that the area to be drilled hangs off the edge. Drill holes in a line down the center of each cleat every 6 to 8 inches with a ¼ inch bit.

Hold each cleat in place on the brick lined up with the cleat lines you drew. Drill through each pilot hole to mark the brick with a 3/16 inch rotary mason's bit to a depth of 1/8 inch. Set the cleats aside and drill a pilot hole on each mark to a depth of 2 inches. Blow the dust from the holes. Set each cleat in place and drive a 2 ½ -by-1/4 inch tapcon style concrete screw through each pilot hole into the brick. Drive the screw in until the cleat is pulled tight to the brick.

Place the mantel over the cleats and press it tight to the brick. Nail the mantel to the edges of the cleats with an air powered finish nailer. Drive one nail every 8 to 10 inches. Caulk around the edges of the mantel with 100 percent silicone caulk to seal it to the brick. Fill the nail holes with an appropriate color of wood filler putty.