LAS VEGAS -- New houses today are almost twice as big as they were in the 1960s. But America's love affair with large houses may have reached its zenith.

And buyers over 50 who are ready to downsize may help drive that trend.

"People still want larger homes than they're living in," said Gopal Ahluwalia, head of research for the National Association of Home Builders. "But the average national home size is stabilizing."

The average house built in America last year was 2,320 square feet, about the same as in 2002 and down from more than 2,330 square feet in 2001, according to the Washington-based home builders group.

"We are finding that people are more and more concerned with the features in the house," not just size, Ahluwalia said Tuesday at the National Association of Home Builders annual convention in Las Vegas.

The group's just-finished survey of potential new-home buyers yielded a few unexpected results.

"We asked them if they wanted a bigger house with fewer amenities," he said. "Over 63 percent said they would take a smaller house with more amenities."

But most buyers say they want more than 2 1/2 bathrooms and three or more bedrooms. And they want special rooms, including home offices and media rooms.

"More people are saying, 'We will buy a house without a living room,'" Ahluwalia said. "In many homes, the living room has vanished." About 40 percent of houses built last year were without a formal living room, compared with only 33 percent in 2000, according to the surveys.

But "the dining room, whether they use it or not, is not going anywhere," he said.

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The appeal of multistory houses is waning.

The number of buyers who said they wanted a house with two or more stories fell from more than 50 percent in 2000 to about 35 percent last year.

"This is the most surprising finding," Ahluwalia said. "For the last 30 years, the share of two-story has been rising."

Builders say two-story houses have become the norm in many communities because of high land costs.

"Our lots are getting smaller, and our houses are getting bigger," said Colorado-based housing consultant Chuck Shinn. "It makes it very difficult to build a single-story house."

For the first time in 2003, the National Association of Home Builders surveyed home buyers in different ethnic groups about their housing tastes.

Most Asian, Hispanic and black new-home buyers want larger houses than white buyers, the research showed. And they're willing to pay more for them.

Black and Asian buyers said they wanted more bedrooms. Otherwise, the preferences of the various ethnic groups are similar.

Builders and housing researchers are also keying on what they expect to be a driving segment of the housing market during the next decade -- aging baby boomers who plan to downsize.

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"Ten thousand people a day (in America) are now turning 50," said Florida architect Quincy Johnson. "This is the fastest-growing housing market in the country, if not the world."

About 39 million Americans will reach age 55 in the next five years. And Americans over 50 control 75 percent of the country's wealth, Johnson said.

"These consumers have money and want well-designed homes to accommodate their active lifestyles," he said.

Boomer buyers usually want smaller, amenity-packed houses and fewer chores around the house.

"They are not looking at this stage in life to mow the lawn and rake the leaves," said Pam Vaughn, whose New Jersey planning company has interviewed boomer buyers in several cities.

"Cookie cutter neighborhoods where all the homes look alike turn them off," she said. "They don't see themselves as old now or ever getting old. Living in an active adult community carries a stigma."

And just because a home is smaller doesn't mean it will have fewer frills, said Maryland designer Georganne Derick.

"They want two dishwashers in the kitchen, and often two refrigerators," Derick said. "They have two home offices, his and hers.

"Empty nesters have lived the frazzled life," she said. "Both of them had careers; that's why they can afford two of everything."