How to Make a Mantel Out of MDF Board

Measure the width of your fireplace, using a measuring tape. Add at least 12 inches to that measurement to determine the length of your fireplace mantel. This will result in your mantel extending 6 inches on either side of your fireplace; add more than 12 inches to make your mantel longer.

Cut a piece of 1/2-by-4-inch MDF board to the length measurement determined in Step 1, using a circular saw. This board will serve as the breastplate for your fireplace mantel.

Hold the breastplate flat against the wall, centered above the fireplace. Adjust the MDF board so its bottom edge is at least 60 inches off the floor. This is the standard height for fireplace mantels, but you may install yours at a different height if you desire.

Make pencil marks along the top and bottom edges of the breastplate every 6 inches. If the wall above your fireplace is brick, adjust the spacing of these marks so they align with the mortar joints between bricks. For drywall, use a stud finder to locate the wall studs and align the pencil marks with the studs.

Bring the breastplate down from the wall. Pre-drill holes through the breastplate where you made the pencil marks, using a power drill.

Hold the breastplate up against the wall in the same position as before and drive 3-inch masonry screws through the pre-drilled holes in the board into the wall. If the wall above your fireplace is drywall, drive 3-inch wood screws through the breastplate into the wall studs.

Cut a piece of 1-by-6-inch board to the same length as the breastplate, using the circular saw. This board will serve as the shelf for your mantel. If you desire a wider shelf, use a 1-by-8-inch board instead.

Lay the 1-by-6-inch MDF board flat on the top edge of the breastplate. The back edge of the 1-by-6-inch board should be flush with the wall, and the ends should be aligned with the ends of the breastplate.

Drive 2-inch wood screws down through the mantel shelf into the thickness of the breastplate to secure it in place. Fill the screw holes with wood filler. Once the wood filler has dried, sand the surface of the wood smooth with fine-grain sandpaper.

Paint or stain your completed MDF mantel to match the decor scheme in your room. Because MDF does not have the same kind of visible grain as traditional hardwood, painting your mantel is usually the better option.