How to Build Tall Fireplace Mantels

Sketch a design on paper that takes the proportions of the room into consideration. Add a board underneath the mantel and between the columns, known as a frieze board, if you wish, because a tall mantel will give you extra room. Consult local building regulations for any restrictions regarding clearances.

Measure and mark on the wall the layout for the surrounding columns, or pilasters, and mantel.

Cut and install furring strips, or narrow blocks of wood, to the wall, mimicking the layout. This will give the fireplace surround the dimension that is needed and provide the anchor to the wall that is necessary to make it sturdy. Use drywall anchors to secure nails in spots on the wall where a stud cannot be located.

Build the pilasters out of three pieces of MDF board or pine, forming a shallow box. The columns should measure from the floor to the bottom of the mantel. Glue the pieces together with carpenter's glue, and then nail the three pieces together.

Attach the surround pilasters to the wall by nailing them to the furring strips. Check for plumb and level.

Install furring strips to build out the mantel frieze board. Add an arc to the bottom of the board, if you want, using a table saw.

Sand the frieze board, then nail it to the wall and the columns, checking for level.

Begin adding crown molding to the top of the legs and the frieze board, using several varieties of molding to provide the look you desire. Glue the molding in place, then nail in place with finish nails. Use a mitre box to angle the ends of the molding for a professional look.

Cut the mantel shelf to size. Use a router to smooth out the edges.

Glue the bottom of the shelf, then place the mantel shelf on top of the columns and frieze board, checking to make certain it's centered and level. Nail into place.

Add molding to the base of the columns and to the mantel shelf, if desired.

Counter-sink all exposed nails with a nail set and fill the holes with wood putty. Caulk any seams. Sand the entire mantel, then paint it.