How to Add a Mantel to an Existing Fireplace

Lay down a protective tarp on your floor to guard against excess dust or scratches from the new wood. Set the mantel shelf top down on the tarp.

Assemble the mantel's legs. Follow your specific product's instructions for this step; in general, you will insert the legs of the mantel into the bottom of the shelf and turn the dowel screws until they are secure. Test the legs by gently applying pressure to the joints; the joints should not wiggle or twist after you have secured the screws.

Turn the mantel right side up and place it against the wall, centered around the firebox where you intend to install it. Use a level to check for an even surface with the back of the mantel against the wall, as well as from front to back across the shelf. If necessary, insert thin wooden shims under one or both legs to achieve level.

Trace the outline of the mantel onto the wall in pencil to create a guide for your installation. Gently lay the mantel face down on your tarp once the outline is complete.

Measure the inside width and length of the shelf and legs from behind the mantel. Use a circular saw or hand saw to cut 2-inch by 4-inch pieces of wood to fit inside each of these areas of your mantel. Always wear protective goggles and gloves when cutting wood.

Line up the 2-inch by 4-inch pieces inside the mantel to make sure they fit. These pieces, known as cleats, will help hold the mantel in place. Hold up each cleat in its corresponding place on the pencil outline of the mantel. Drill four ½-inch-diameter holes through the cleats and into the wall with a carbide-tipped masonry drill bit. Space the holes evenly apart across the surface of each cleat.

Insert 2-½-inch concrete screws through each pilot hole in each cleat and into the wall with your drill. This will secure the cleats in place.

Set the mantel over the cleats so that it aligns with your pencil outline. Press the mantel firmly against the wall in all locations. Drill 2-inch finishing screws into the back of the shelf, connecting it to the cleat every 16 inches across the surface. Repeat installing the screws every 16 inches down the sides of the leg pieces to hold your mantel in place.

Hammer 4D finishing nails through thin pieces of matching molding along the inner length of the mantel, covering any gaps between the legs and the fireplace surface. Fill in the screw and nail holes with filler putty.