Many people probably search for a home with three dominant criteria in mind: size, cost and location.

To most consumers, questions of housing architecture, style, density and urban design usually take a back seat to concerns about closets, kitchens, bathrooms, security, utilities, taxes, mortgages and maintenance. Housing developers, understanding the interests of their market, naturally tend to build and merchandise housing to address these consumer concerns.

On the other hand, architects and planners tend to think about housing quite differently than consumers. Designers categorize housing by "type," which refers not to the amenity package offered with a dwelling, but rather to its basic physical characteristics -- its form, and how dwellings are placed within urban or rural settings.

Housing density (number of dwellings per unit of land area) affects land value, traffic and the need for roads and public services -- schools, utilities, police and fire protection. Even microclimate (patterns of shading, wind, air quality) is affected. Density also has an impact on commerce, influencing the market potential for community retail services. Housing type, density and method of dwelling aggregation, in turn, determine a neighborhood's physical character.

To regulate the physical character of cities and suburbs, legislated zoning codes use dwelling type and density designations to categorize residential zones. They narrowly define unit types -- single-family detached houses, town houses, walk-up or high-rise apartments -- and stipulate maximum densities varying from one dwelling unit per acre (or less) to hundreds of units per acre.

The free-standing house typifies the lowest range of density and the most restrictive land use. Many people take for granted that the single-family detached (SFD) house is the ideal home, the desirable norm for those who can afford it. Other types of housing, especially multifamily housing, seem to be no more than necessary, acceptable deviations from the norm.

This long-standing cultural bias is rooted in the belief that prosperity, security, freedom and personal fulfillment are inexorably linked to ownership, control and occupancy of land, the "manor" and its "manor house." Land traditionally was the only true and permanent form of wealth. Historically, such dominion also had practical advantages; land could be used for agrarian, commercial, recreational and, with enough gardeners, aesthetic purposes.

Few house lots are literally manors. Lot sizes vary widely, from a few thousand square feet (the District's SFD lot size is 5,000 square feet) to several acres. A mobile home lot can be as small as 2,000 square feet, a lot size commonly found in dense urban settlements in Europe, Asia and Latin America.

Many American SFD houses of the 18th, 19th, and early 20th centuries sat on small lots with little or no street setback except for a porch or entry stoop. Their owners may have been conscious of economies afforded by density. Not only did each house consume less land, but the infrastructure required for each house -- roadway, curb and gutter, sidewalk and utilities -- was less. Despite proximity to neighbors and passers-by, privacy could be achieved through the simplest of architectural devices -- shutters, curtains, closed windows and fences.

Small SFD lot sizes do not result in spacious front, rear and side yards. However, densely arranged detached houses can be situated on small lots with great architectural payoffs. Judiciously placed walls can help make very comfortable, intimate private gardens or yards. The houses themselves, spaced closely together along the street or around a court, can create equally intimate and charming streetscapes.

But intimate charm goes just so far. The automobile, an apparently unlimited supply of land and the symbolic strength of owning a house with "grounds" reinforced the 20th century American trend toward subdivisions, with mini-estates lining relatively wide streets.

Thus, instead of lots containing a few thousand square feet, with widths from 30 to 50 feet and depths from 80 to 120 feet, suburbia opted for much larger lots, 80 feet or more in width and 150 to 200 feet in depth. While smaller lots might yield densities of eight to 12 units per acre, conventional subdivision lotting typically yielded only two to four units per acre.

Houses retreated farther from the street, producing spacious front lawns. Streets widened, sometimes to the point of losing their domestic scale. Only after many decades might saplings planted along the right of way mature into trees with columnlike trunks. Nature, not architecture, would vitalize the street space.

In the 1960s and '70s, planners and architects encouraged developers to build, and government authorities to sanction, the clustering of SFD houses. This land-use strategy generally maintains overall tract density at levels prescribed by zoning and also allows clusters of smaller lots integrated with common open land. In some cases, cluster houses can abut their own lot lines on one or two sides to increase yard sizes on opposite sides.

Clustering increases net density, respects topography and other natural features, reduces lot-improvement costs and, of great importance to designers, enhances possibilities for creating a tighter, more intimate residential streetscape within each housing cluster.

However, many SFD homes still are built on conventional subdivided, bulldozed lots with marginally useful side yards, long utility branches and meandering streets. Little, if any, of the original site features -- topography, vegetation and trees -- remain. Despite architects' romantic attachment to the imagery and density of Edgartown, Savannah or Kalorama, and despite the potential economies inherent in developing land more intensely, the forces of consumer taste and automobile accommodation remain very powerful. Equally important, most homeowners desire neighbors who share their values and status. Designers may idealize the intermixing of land uses, densities and socioeconomic classes, but the average consumer probably prefers a detached house in a community of similar houses occupied by similar people. Aspiring to any other model would require an American residential revolution.

NEXT: House history.