Fireplace Mantle Instructions

Measure around the top three sides of your fireplace opening to figure out how large to make your mantel pieces. To satisfy the National Fire Code, you should add an extra 1-inch of distance between the bottom of the mantel and the fireplace opening for every 1/8-inch your mantle protrudes from your fireplace surround.

Using the measurements for the sides of the fireplace, cut your MDF into five pieces which you will use to construct two backless, bottomless rectangular boxes; these boxes will be you mantle legs.

Cut the side pieces of the boxes to the predetermined length, and then cut them to 6-inches of width, or to whatever width measurements suit your fireplace. Cut the top pieces to 6-inches by 6-inches, or whatever measurements best suit your fireplace. Cut the front pieces to your predetermined width and length.

Construct the boxes using small nails. Place the boxes on the floor, with the open back facing the floor. Cut off the bottoms of your newel posts to match the length of your boxes. Set your two newel posts on top of the box faces, positioning them in the center. Glue down.

Begin cutting your mantel shelf, which will be another rectangular box, this time only backless. Cut the top and bottom sides of you shelf to the length earlier decided and a width that matches the height of your crown molding.

Choose a depth for your box and cut the front piece of your shelf to that measurement and the length of your top and bottom pieces. Cut the side pieces of the shelf using the width you chose for your top and bottom pieces and a depth from your front piece.

Assemble the pieces into a rectangular, backless box using small nails.

Measure the insides of your three backless boxes. Cut three pieces of MDF to match these measurements; these are your cleats.

Dry fit your mantel against your fireplace, checking with your level for evenness. Draw an outline around the mantel. Lay the mantel back down.

Draw another line 3/4-inches inside this line, since your MDF is 3/4-inches wide. Check your line for straightness using the level. Place your shelf cleat directly beneath the innermost line for the shelf. A few inches from one side of the cleat, drill a pilot hole through the cleat and into the stone or brick fireplace surround; use your masonry bit.

Drill at least three more holes across the length of the cleat, reaching the other side of the cleat and keeping the spaces between the holes even.

Change the bit on your drill to prepare to drill screws. Drill your 2-inch wood screws into the pilot holes you just drilled, attaching the cleat to the wall.

Put the masonry bit back on your drill. Set one of your side cleats against the fireplace, directly inside one the innermost lines that mark the outlines of the mantel sides. Drill pilot holes down the length of the side cleat. Repeat with other side cleat.

Change your bit again and attach the side cleats to the wall using your wood screws and pilot holes.

Fit your mantel pieces of the cleats; they should fit very snugly. Nail down the side mantel pieces into the cleats beneath; nail across the top back of the mantel shelf into the MDF cleat beneath it.

Miter cut your crown molding pieces to the width and length of you mantle shelf; nail these three pieces to the front and sides of your shelf.

Fill any visible holes with wood putty. Paint over the mantel pieces to create a cohesive look and hide any visible construction elements.