Not too many years ago, the main thoroughfare of Edgewater, New Jersey, had the feel of a back road meandering through landfills and old factories.

These days, it is a jumble of new apartment blocks, condominiums and shopping centers after developers discovered its priceless view of the Hudson River and New York City.

But Edgewater's construction boom also highlights a trend in U.S. housing: the incredible shrinking lot. Where once there was a single family home with a small garden, there is now a townhouse development. So-called McMansions, whose modern walls stretch almost to the neighbor's property line, are everywhere.

Long a staple of middle-class life, the detached single-family home with a large yard is not only becoming less affordable but also harder to find. Lot sizes are decreasing, and attached houses and condominiums are gaining ground in some hot markets.

According to U.S. Census data, the median new one-family house, a category that includes attached units, was 2,227 square feet in 2005, up 40 percent from 1976. But the median lot size has fallen 12.6 percent to 8,847 square feet.

Land costs are going up continuously, said Gopal Ahluwalia, staff vice president for research of the National Association of Home Builders trade group. The home buyer is willing and has been willing to buy a smaller lot, but not a smaller house.

In today's expensive housing market, some people undoubtedly live in apartments or attached homes because they can't afford anything else. But Ahluwalia noted: A guy who's buying a million-dollar townhouse is buying by choice.

ACREAGE EQUALS PRIVACY

The homeowner population, which used to consist mainly of families with children, has expanded to include singles, retirees and others who don't want the upkeep of a large house and yard.

Detached single-family homes have accounted for about more than 60 percent of occupied U.S. housing for at least the past eight years, according to census data, but other types of dwellings are gaining ground in some markets, particularly in the U.S. Northeast.

Of all construction permits issued in the region last year, 62 percent were for single-family homes (including townhouses and duplexes), down from 78 percent in 1997. The category's share still rose nationwide to 78 percent from 74 percent.

Experts say the growth of attached and multifamily housing is happening primarily in East and West Coast areas where land has gotten particularly expensive.

Some say this trend is a good alternative to suburban sprawl when the denser housing takes the form of a diverse neighborhood, with businesses, shops and public space all located within walking distance.

That's still a big change for a country that measures privacy by the amount of acreage that separates a house from its neighbors.

The most common amenity in the United States is the yard, said Andres Duany, a founding principal of new urbanist architectural and planning firm Duany Plater-Zyberk & Co. of Miami. If you want privacy, that's fine, you just move that neighbor away. It's not because people want more lawn to mow.

But even proponents of density don't always like the results.

In her book, The Perfect $100,000 House, Karrie Jacobs described how an eclectic mix of styles in the Palisades Park neighborhood where she grew up had given way to the two-family anonymous brick things that were now the norm in this part of New Jersey.

Not only were there no yards, there were no trees or bushes or any of that anymore, and there were no people outside, she said in an interview. I wonder if it was more than just a real estate issue, whether it's more of a broader cultural issue, that people's relationship with the outdoors in some cases is a little bit estranged.

'CRUEL AND MANIPULATIVE'

As in Edgewater, developers nationwide are generally putting attached housing on properties like failed shopping centers, in ravines and on former industrial sites, areas that were bypassed for decades because the economics didn't work for single-family, said David Dixon, principal of the Boston-based architecture and planning firm Goody Clancy.

Whether the housing is dense or sprawling, experts agree that the key to privacy lies in construction and design quality.

In markets where you are paying hundreds of dollars a square foot, Dixon said, you can afford to sound-insulate.

Roger Lewis, professor emeritus of the University of Maryland School of Architecture, said he had seen single-family houses where the windows face each other across the sideyards. You might as well have a party wall, he said.

I've been in apartments where you can hear everything, he added, In others, there's been a lot of attention given to sound transmission and acoustical insulation. Usually it does cost a little more money.

Because of increased regulation, he noted, today's new homes are better built than those 30 years ago.

Duany has taken privacy a step further in Alys Beach, a new resort town on the Florida Panhandle. While the community will offer such urban features as a plaza with shopping and restaurants, there are also attached and detached homes, each wrapping around its own courtyard.

The Alys Beach houses start at $1,165,000, but Duany said his firm had adapted the concept to 1,100-square-foot units that will cost only about $100,000 to construct. A project is planned for the Baywater section of New Orleans as part of the post-hurricane rebuilding effort.

The courtyard concept stands in stark contrast to the well-known town of Seaside, Florida, which Duany's firm designed in 1980. In an effort to bring people together, he said, the planners put walkways behind each house to violate the privacy of the backyard and draw them to the front porch.

In an analysis that we did some 10 years later, we decided that this was cruel and manipulative, he said, because people have the right to a public front and a private back ..., the right to public outdoor space and the right to private outdoor space.

New Jersey Privacy