The average family may be smaller than it was 10 years ago, but the average single-family house is larger — and more luxurious. It has more bathrooms, higher ceilings, more elaborate master bedrooms, and bigger kitchens and outdoor space.

So what will the average home look like in the next decade?

More than 300 architects, designers, manufacturers and marketing experts interviewed by phone or surveyed by the National Association of Home Builders last year predicted that the average U.S. house in 2015 will not be any bigger. What it will be, they said, is much more luxurious.

"You wouldn't consider buying a car without power windows, a CD player, cruise control," said Tony Letke, senior vice president of Sykesville, Md., custom home builder Mueller Homes. "Look at houses, and, my goodness. The quality of the lighting, the quality of the appliances, the amenities in general are no longer really considered extravagant and upgrades. People want their homes well-equipped, as they do their automobiles."

Blame — or credit — baby boomers. "They started buying homes not just to meet functional needs but to fit a lifestyle," said Gopal Ahluwalia, staff vice president for research at the builders association.

Another generation, those born from 1965 to 1977, are now in their prime home-buying years. And they're just as demanding, Ahluwalia said. "They also want everything."

In its "Home of the Future" study, to be published this month, the builders association predicts that the average size of a single-family house will be 2,300 to 2,500 square feet, about what it is now or even slightly smaller. High ceilings — about nine to 10 feet — will become the norm. So will 2 1/2 to 3 1/2 bathrooms, which is at least one more than the average house had in the 1970s.

In high-end houses, those with 4,000 or more square feet, dual master-bedroom suites will become even more popular than they are now and will include sitting rooms, bathrooms and walk-in closets.

In both upscale and average houses, the family room will get much larger, while the living room will continue to shrink — a testament to the popularity of casual entertaining.

"The formal living space isn't as important," said Andy Rosenthal, president of Rosenthal Homes in Potomac, Md. "As a baby boomer, when we grew up, we all had living rooms, but we weren't allowed in there. Now we don't want living rooms because we weren't allowed in there anyway."

Ahluwalia said that people will want their houses to be more open, airy and bright. They'll ask for large kitchens with islands, fewer walls separating their dining rooms or family rooms, and recessed lighting. Plain white walls won't do; bold colors will be in.

And they'll probably want things they don't need.

In parts of the country with colder weather, a fireplace, for example, has become an object of desire.

The same goes for garages, which will probably get much larger, especially in pricier homes.

"Even people who don't have three cars want to have a three-car garage," Ahluwalia said.

Technology will become a more integral part of the house, the study found.

Universal design, a concept that makes homes accessible to all people regardless of age or disabilities, will also find a place in new-home construction.

One national trend experts expect is more luxurious outdoor spaces.

The association's study predicts that outdoor kitchens complete with sinks, refrigerators and cooking islands will become more popular in upscale homes.

The survey also found that "green" methods will become more widespread. The builders association predicts that the home of the future will have water conservation devices and energy-efficient appliances, among other features.