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Building a Fireplace Mantel

Construction How-To, Construction How-To, Finish Carpentry, Fireplace, Mantels. Trim, Trim Carpentry January 3, 2007 Sonia


This classic mantel features an arched frieze and can be built using basic carpentry skills.




You have many options when it comes to fireplace design, like fuel types, locations, firebox liners, ventilation systems and masonry treatments. Mantels alone include a whole array of choices. A fireplace mantel can be natural wood or painted. It can include legs (pilasters) or may even incorporate a bookcase or other storage on each side. Some mantels extend all the way to the ceiling and include alcoves for displaying art or housing video screens. Surface design options include appliqués, fluting or surface designs. Raised or recessed panels can also be incorporated into the design. Mantels can be as rustic as a log set in river rock or as refined as the most elegant piece of furniture.

First sketch your design on paper.

Plan the Design

Mantels are either built in place or built as a unit (on or off site) and installed. How you attack your mantel job depends on your starting point. If you are building a mantel on a new fireplace install, check with any other trades for the order in which to do the job.

Some stone masons prefer to have the mantel in place before setting any surround materials while others would like to set the masonry first and then have the mantel built around it or installed over it. This doesn’t mean that the mason or stone setter should call the shots, but if they have a preference you might as well ask them before ignoring them.


Starting with the firebox, measure and mark the width of the masonry surround, plus (3/4″). Measure from both sides of the firebox as well as above the firebox.

No matter the design or sequence of the mantel install, it must be built and installed with strength in mind. While mantels are decorative in themselves, they also function as a display shelf for the most precious of family heirlooms, so we have to make sure they are sturdy and well anchored to the house.

If there is no wallboard up, you have an opportunity to add some framing to help anchor the mantel. Do so as long as it doesn’t violate the required clearances for combustible materials.

Besides being sturdy, the mantel shelf itself must be deep enough to accommodate the items you wish to display there. Also, determining the mantel size is the size of the room. If the room is large and has high ceilings, you can and should build a larger mantel. Intimate spaces, on the other hand, should not be overpowered by a bulky mantel.

As the mantel shelf extends beyond the face of the legs, the wider it will be. This is because the corbels and crown moldings, which support the mantel shelf, extend to the sides proportionally to the depth.

The mantel design for this particular project is built around a zero-clearance firebox with a stone surround, but it will work as well with any number of surround treatments like brick or tile. The homeowner wanted a substantial sized crown molding, so we got the look by building up (or layering) two different moldings.

After measuring and marking your layout lines, cut and install the backing for the legs. The legs should extend from the bottom of the floor to the bottom of the mantel shelf. Horizontal blocks can serve as backing for the legs, depending on framing location.

Rip the side walls of the mantel legs to width. Fasten the legs’ sides and faces with glue and nails.