Mantels play a special role in the American home. They often serve as the focal point of important rooms--such as the living room--where functions that bring together family and friends take place. Captured in photos, trophies, and mementos, a family's proudest moments rest on the mantel, demonstrating to visitors the soul and character of this particular clan. Thus, it makes sense architecturally for the design of the mantel itself to embody the soul and character of the surrounding house.

Such was the idea behind these two mantels by San Francisco architect Dan Phipps, which preside over the living rooms of two local Modern houses. Although they occupy separate homes, each mantel reflects the pared-down simplicity of its environment. In particular, hidden support systems keep fussy details to a minimum.

In the first house, Phipps wanted a maintenance-free material for the mantel that would match the color and feel of the redwood trees outside. So he used Cor-Ten steel for both the framing and the mantel itself; when rusty, the metal mimics almost perfectly the distinctive hue of redwood bark. (By "watering" the steel daily with a spray bottle while it was on the construction site, the owner hastened the rusting process. Otherwise, it would have taken about a year of natural weathering to achieve the desired finish.) Phipps made the 335-pound steel beam that serves as the mantel appear to float above the fireplace by hanging it from hidden steel angles. He closed off the ends of the beam with Cor-Ten steel cover plates, which are attached with hidden welds. The surface of the steel is sealed with beeswax.

In the second house, Phipps also used steel as a finish material, but in this case as a facing for the fireplace surround. The mantel itself is concrete, a material that shows up elsewhere in the house in the form of tiles. He hired Dave Holsenback, of Reification, also in San Francisco, to "patinize" the steel with a special acidic process that lends the metal a rich, warm character. And he hired specialists from the local firm Buddy Rhodes Studio to give the concrete a unique, earthy look of its own. They dry-packed the concrete into forms, which created little air pockets on the surface that were later filled with a lighter-color grout. The finished material boasts the texture of travertine and--thanks to coloring agents--the color of limestone.

Early in the process, while the concrete was still malleable, Phipps had cast a long, deep slot into the rear of the mantel. Hanging the finished piece involved sliding a 48-inch-long steel anchor plate attached to the wall framing into this slot.

Most of the weight of the steel mantel hangs from a continuous angle set under the top flange, with secondary support and bracing provided by two clip angles attached to the bottom flange at either end.

Phipps squeezed adhesive into the concrete mantel's cast-in slot to attach the ledge more firmly to its support. He also bolted the five vertical anchor straps welded to the rear of the horizontal plate to each stud, at the top and at the bottom. He used mill board (or MDF board) behind the steel facing, which provides a firm support for the anchors.

Rick Vitullo, AIA, is founder and principal of Vitullo Architecture Studio, Washington, D.C.

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