How to Build a Mantel on Brick

Measure the width of your fireplace using a measuring tape and add 12 inches to find the width for your new mantel. Your mantel will extend beyond the edges of your fireplace by about 6 inches on each side. You may add more than 12 inches to the width of your fireplace if you desire a longer mantel.

Use a circular saw to cut a piece of 1-by-10-inch hardwood to the measurement you determined in the previous step. Make small pencil marks along the top and bottom edges of this piece of wood approximately every 8 inches.

Hold the 1-by-10-inch piece of hardwood flat against the wall above the fireplace. Adjust the height of the board so the bottom edge is about 60 inches off the ground. Align the pencil marks with the mortar joints between the bricks in the wall.

Bring the board down from the wall and drill holes through the top and bottom edges of the board where you made the pencil marks. Hold the board once more up against the wall above the fireplace in the same position as before. Drive 3-inch masonry screws through the holes in the board into the mortar joints between the bricks to secure it in place.

Measure the distance between the bottom edge of the board you just installed on the wall and the surface of the hearth. Cut two pieces of 1-by-4-inch hardwood to this length. These two boards will serve as the vertical sides for your mantel and the 1-by-10-inch board you already installed will serve as the breastplate.

Hold the two 1-by-4-inch boards flat against the brick wall, sandwiched vertically between the bottom edge of the breastplate and the hearth. Align the outside edge of the vertical boards with the ends of the breastplate.

Make pencil marks approximately every 8 inches along the sides of the vertical boards, aligning the marks with the mortar joints between bricks. Drill holes through the two vertical boards and attach them to the wall by driving 3-inch masonry screws through the boards into the brick wall.

Cut a piece of 2-by-6-inch hardwood to the length of your breastplate using the circular saw. Lay this board flat on its widest edge along the top edge of the breastplate so the back edge of the board is flush with the wall. Drive 3-inch wood screws through the top of the 2-by-6-inch board into the breastplate to secure it in place.

Cut strips of decorative trim or crown molding to the length of the breastplate and the height of the vertical sides. Experiment with different arrangements until you find one you prefer.

Install the trim by applying a bead of wood glue to the back and pressing it firmly against the wooden mantel frame in the desired position. Drive nails from a nail gun through the trim into the mantel frame to attach it.

Fill all nail and screw holes in the mantel frame and trim with wood filler. Allow the wood filler to dry completely and sand the surface of the wood smooth using fine-grain sandpaper.

Paint or stain your completed mantel to match the decor in your room. Once the paint or stain has dried, apply a coat of clear varnish or polyurethane to protect the wood.