Here is how a Period style works: First we must abandon the notion of rules. As the respected architect, planner, and teacher Jaquelin Taylor Robertson has pointed out, the various styles that history has left us are not rule-based codes; rather, they are gene pools in which traits, grouped by families, are subject to selection, combination, mutation, and adaptation over time. The descent and dissemination of these gene pools is like the breeding of flowers by a gardener: New varieties, hybrids, and occasional surprises are the norm; pure stock is rare. The historical artists and designers saw themselves as conservators of this genetic material, and their garden encompassed all the architecture and design known to them.

Despite the variations, certain traits endure, usually because they work exceedingly well. Consider the typical American center-hall-plan house. In this pattern, the hall is the main entrance and usually includes the staircase. Living room, dining room, and study open off to the left and right of the hall; the back door of the hall usually leads to the garden. Often the most elaborately finished room in the house, the hall is designed to make an instant impression.

We can trace the genealogy of this arrangement back to our friend Palladio, for whom the center hall was the primary public space of the house, often beautifully decorated with mural paintings by the likes of Veronese or Tiepolo, with more intimate rooms opening to either side. This scheme was reflected in the facade, which featured a central portico and balanced windows. Palladio's Villa Badoer in the Venetian countryside has such a center hall running the full depth of the house. Although the hall does not include the stair, it is the beginning of the broad center halls that would appear later. (Fig. 1)

The English adapted Palladio's model for their country houses, grafting it onto an even-older native tradition, the hall and screens passage of the Medieval English house. We can see this amalgam in Thorpe Hall from the 17th century, where a narrow hall runs past the main living space (separated from it by columns) through to the rear of the house. What in earlier practice had been a mere circulation passage along the side of the great hall was soon doubled to provide access to rooms on both sides of the passage. Making this passage broader and including the stair produced the Anglo-American center-hall-plan.

The fully developed pattern may be seen at Westover on the James River in Virginia. Immediately a problem arose: When the stair rises in the hall, the space appears off-center. At Westover, the seven-bay symmetrical facade conceals the off-center shift of the stair hall, which allows the hall to have one of the facade windows and accommodates the intrusion of the stair into the hall space. The rooms on the two sides of the hall are consequently of different sizes and orientations (one side having two facade windows and the other three), a fact that is not apparent from the exterior. (Fig. 3)

Fig. 3		Fig. 3. Westover, Charles City County, Va., 1725. Plan and entrance facade. The hall runs the depth of the house and is broad enough to be a room in its own right. Note the asymmetry of the hall with respect to the facade windows, allowing a window at each end of the hall and different-sized rooms on either side.
Fig. 4. The Colonel Robert Means House, Amherst, N.H., 1785. Plan. A New England variation of the type, placing the stair rail on the hall's centerline.		Fig. 4
Variations may be seen in American designs between the Virginia and New England practices. The Robert Means house in Amherst, N.H., built about 60 years after Westover, shows a more-regular symmetry in the placement of the hall, but differs from the Virginia house in that the rooms off the hall are nearly identical and the windows are grouped in pairs rather than regularly spaced on the facade.

At the turn of the 20th century, the Colonial Revival style re-established the center-hall-plan house and added new variations. In the 1920s, Philip Trammell Shutze designed Swan House in Atlanta, Ga., with a beautiful freestanding circular stair at the far end of the center hall. The entry facade has a very Palladian columned portico while the garden facade follows the pattern of the Renaissance villas outside of Rome. A case of hybridization indeed, and so successful that the amalgam appears perfectly natural. (Fig. 5)

Fig. 5

The genealogy of the center-hall-plan continues in the present generation in the work of many architects who are reviving traditional practice. In one of the author's own designs, the center hall recalls the old English screens passage. Here the living room is separated from the hall by a row of square columns, with the kitchen and dining room/library on the opposite side beyond the stair. In this plan, the living room and center hall together become the center of the house. The regularly shaped and proportioned rooms related by axial views result in a feeling of spaciousness not often afforded by the historical examples. (Fig. 6)

Fig. 6

All these houses share certain stylistic traits while also introducing invention and variation in response to different times, places, and ways of life. Jaquelin Robertson identifies four gene pools that have provided most of America's traditional architecture: the English, Dutch, French, and Spanish. We can distinguish these four by their differences: For example, the French usually place the stair in a separate room and the center hall is rarely used. On the other hand, all four traditions have important common elements, such as the use of the classical orders. In the last century other gene pools from farther afield have entered American architecture: Asian, African, indigenous, and other traditions have enriched our building practices. The challenge today is to maintain this genetic material that we have inherited from the expert breeders who preceded us, while responsibly adding to it.

Designing a new building in a traditional style is more than just combining disparate elements into a melange. The traits must work together, they must satisfy our aesthetic and practical requirements, and they must result in a hardy new plant that will flourish in its new setting. But how might a designer fluent in a particular historical style solve a problem that didn't exist when the style arose originally? How can we find a Period solution to air-conditioning grilles or large-screen televisions? How can one design an addition to an historic house which looks like the original architects returned a hundred years later to enlarge the house themselves? It is instructive to see how the Colonial Revival architects adapted 18th-century house types to include such modern innovations as indoor bathrooms, closets, kitchens, and garages. Shutze and his colleagues Charles Adams Platt, Dwight James Baum, and William Lawrence Bottomley, to name a few, were expert at adapting ancient models to new needs. Designers today are doing the same by bringing the period-style mind to bear on present-day needs. One day future commentators will look back at the period design of our time and come up with a label for it. Perhaps the best advice is not to worry too much about objective historical accuracy while, at the same time, ignoring the pressures to conform to a predetermined program for what design of our time ought to be. It is enough to concentrate on what is appropriate and suitable and let history take care of itself. The period style of our own day is (as it always has been) largely out of our control and, like any breed, will undoubtedly take on a life of its own, much to our surprise.

Steven W. Semes is an architect practicing in New York City and East Hampton, N.Y. He is a Fellow of the Institute for Classical Architecture and a former Director of Classical America. He is co-editor of the forthcoming book Georges Gromort's Elements of Classical Architecture, to be published this year by W. W. Norton and Company.