Building an elaborate mantelpiece can be an intimidating task. That's why I like to think of it as a series of smaller projects — the upper and lower pilasters, the undermantel frieze, the mantelshelf, and the overmantel — that can be built separately. The trick is to figure out how all the parts fit together and then build them accurately and efficiently.
With the materials already on hand, the mantel shown in this article took me and a helper about a day and a half to build. I used a story pole to work out its many details in full scale; pocket-screw construction allowed me to assemble the parts on site with a trim carpenter's basic repertoire of tools. The expressive details that give the mantel its unique look come from different combinations of stock moldings and carvings from White River Hardwoods (800/558-0119, www.mouldings.com)
Planning and Layout
Like scores of other mantels I've built over the years, this one is based on frame-and-panel construction. By changing such elements as the overmantel style, the undermantel frieze detail, the upper pilaster detail, and the type of moldings used for the mantelshelf, I can build the same general style of mantel for a dozen different clients while making each an original.
In this project, the basic mantel dimensions were dictated by the existing brick fireplace, which my clients planned to reface with stone. Inspired by other fireplaces I'd built that the clients had seen, the new mantelpiece was designed to complement the makeover of the entire room, which included a new beam-and-coffered ceiling and new window, door, and baseboard trim.
Basic dimensions. In my area, code requires at least 8 inches of clearance between the side of the firebox opening and the closest trim or cabinetry. Code also requires at least 10 inches of noncombustible material directly above the firebox.
Proportion and layout are crucial to a nice-looking fireplace surround. The author always starts by measuring the width and height of the available wall space, then designs accordingly. Shelf height falls at around 60 inches for an 8-foot ceiling, higher for taller rooms. Panels above the mantel should be at least 4 inches taller than they are wide; sometimes the center panel is wider than the flanking panels. Upper pilasters are typically narrower than the lower pilasters, though centered above them.
I keep these requirements in mind when I establish the height of the mantelshelf, which I base mostly on room size and the height of the firebox opening. In a smaller room with 8-foot ceilings, the shelf may be as low as 60 inches above the floor; in a larger space with tall ceilings, it may sit 68 inches or more above the floor.
Had there been a raised hearth in this project, it could have really limited the detailing above and below the mantelshelf. Fortunately, there wasn't one.
Story Pole Is Crucial
No matter what site conditions I find, I use a story pole to develop the layout. For most fireplaces, I actually do five layouts. Because I always end up making some adjustments as I look at the proportions, I do my layouts in pencil, labeling all the parts and marking their exact size on the story pole.
The author starts by marking existing conditions on the story pole, such as the width and height of the firebox opening, the size of the noncombustible material surrounding it, and the proposed height of the mantelshelf.
Horizontal layouts start in the middle and work outward. Vertical layouts originate from the proposed location of the mantelshelf, go down to the floor, and then work from the shelf up to the ceiling.
Layout 1. Making the mantel work with the width of wall available is usually the greatest challenge, so I do the horizontal layout below the mantelshelf first.
In addition to accounting for the span of the firebox and any noncombustible material, I make sure to leave enough width for the shelf to return to the wall. Determining the pilaster width is the most important part of this layout.
Layout 2. Taken vertically through the middle of the firebox, this layout shows how much room is available for decorative elements under and above the mantelshelf, the shelf height, and the vertical layout of the paneled overmantel.
Layout 3. This layout is taken vertically at the pilasters beside the firebox and shows all of the moldings that will wrap around the pilasters, plus the layout for the corbels that will support the mantelshelf. It also indicates the height and layout of the upper pilasters.
Layout 4. Taken horizontally above the shelf, this layout indicates the width of the upper pilasters and the layout of the paneled overmantel. If the overmantel is a single panel, it should be about 30 percent wider than it is tall. For a three-panel overmantel like the one shown here, I make each panel at least 4 inches taller than its width. Usually the middle panel is 3 or 4 inches wider than the side panels, but all three can be the same width. Upper pilasters are usually narrower than lower pilasters, but must be centered over them.
Layout 5. This is a small layout that shows the projection of the mantel from the wall. (Since there are only four sides to a story pole, I usually fit Layouts 4 and 5 on the same side.) The total mantel projection includes the thickness of the lower pilaster, the projection of the corbel, and the combined projection of the moldings used for the shelf. My shelves typically project from the wall about 11 to 14 inches. For useable shelf space, remember to subtract the thickness of the overmantel that will cover up part of the shelf.
As I juggle the widths, heights, and depths of each part in the layout to get all the components to fit together, I try to offset joints by 3/4 inch (a purposeful step looks better than a gap). I also make sure to allow room for trim that runs from one piece onto the next. For example, the field behind a pilaster must be wide enough to allow the base trim that wraps the bottom of the pilaster to die into a flat space.
Finally, before starting to make sawdust I like to do a rough drawing of each piece, on either graph paper, plywood, or a board. The proportions and measurements come from the story pole. The drawings make it easy to develop a cut list and build each part.