How to Build a Fireplace Mantel Surround

Check local building codes for minimum setbacks from the firebox allowable for wood trim.

Remove any existing trim, using a wide putty knife and a small pry bar. Position the knife between the wall and the pry bar to prevent gouging the wallboard.

Install tile, stone or brick around the firebox if your local building codes require a setback from the fireplace box for wood trim and your fireplace doesn't yet meet these codes. Usually one course of brick or tile will be sufficient. Use the type of adhesive recommended by the manufacturer. Allow to dry, grout around the joints, and wipe off excess.

Locate the wall studs with your stud finder and mark their position. Measure and cut a piece of pine for the horizontal strip that sits under the mantel. The horizontal strip should be cut to fit between the side pieces. Make certain that the horizontal piece is level, and nail it on the wall, predrilling holes and using a hammer and nails.

Cut surround sides (pilasters) so they rest on top of the tile hearth and are in line with the top of the horizontal piece. Apply adhesive in the inner edges that butt up to the horizontal piece, and the bottoms that rest on the tile. Make certain they are plumb and resting squarely on the floor. Attach with nails.

Using a piece of 1-by-10 pine cut to size for the mantel. Attach decorative molding by mitering the corners of the molding and nail to the mantel. Set the molding back from the edge 1/4 to 1/2 inch for an even greater effect.

Position the mantel on top of the horizontal piece and pilasters. Check to be certain it's centered and level, then nail it into place.

Add plinth blocks to top, bottom and sides of the pilasters for extra support and visual appeal.

Add decorative molding to the face of the surround, to the joints between the plinth blocks and the surround, and anywhere else where embellishments are needed.

Spackle any openings and nail holes. Use sandpaper on the entire surface to smooth out. Wipe off with a tack cloth and add varnish, stain or paint.