-- American culture may be obsessed with youth, but when it comes to residential architecture in the 21st century, a hot trend is old age -- and how to design for it.

The realities of growing elderly surfaced repeatedly at the recent American Institute of Architects national convention

In symposiums, in interviews with architects and in the institute's just-released survey about trends in home design, one of the strongest themes wasn't the rediscovery of urban cores or the resurgence of Craftsman, Midcentury Modern or any other style.

Rather, the hot trend was worrying about our physically impaired future.

"The idea is that you want to stay independent as long as possible," said Taal Safdie, principal with Safdie Rabines Architects in San Diego and panelist for a symposium on trends in custom homes.

She cited recent projects that included wheelchair-accessible hallways, handrails in the bathrooms and driveways that run directly to entrances. Owners of these houses have no mobility problems currently, Safdie said.

Results of the American Institute of Architects's first-ever survey on home design trends, released during the convention, backed up that notion. Of the 420 firms surveyed, 62 percent reported an annual increase in the number of projects in which accessibility was an issue, according to Kermit Baker, the institute's chief economist and survey manager.

He said more people were asking for homes with fewer steps and wider doorways. One in four firms reported more clients seeking a single-floor design.

Other trends:

* Multigenerational living. More Americans want home designs that allow one generation to care for another, while still allowing some semblance of privacy. Safdie cited one client in San Diego who wanted three homes built on the same property: one each for herself and her two daughters.

* Accessory dwelling units. With the rise in multigenerational living coupled with high real estate prices, expect to see more garages and detached secondary structures converted into mother-in-law units or other types of livable space.

* Home retreats. One winner of the 2005 AIA Honor Awards for Architecture went to David Salmela, of Duluth, Minn., for a detached sauna he designed for clients in his hometown. He said saunas now are a key element in 50 percent of the homes he designs. The AIA winning design was purposely sited away from the clients' house. "Everybody needs to get away, a place of relaxation," Salmela said, "even at their own home."

* Fewer formal rooms. The number of traditional floor plans continues to decline. Two out of three firms in the new survey reported rising interest in homes geared for casual living, with features such as kitchens opening to family rooms.

Dulcie Horwitz, a Thousand Oaks, Calif., architect, said she would begin work this summer on a home with 2,400 square feet without a formal living room or dining room -- areas that Horwitz calls "pretend rooms" because few people use them.

"In the age of $1.2 million tract homes," she said, citing the neighborhood's median price, "costs force homes to use space better and be better designed."

* Street-side cachet. In one key seminar, panelist Stephen A. Kliment, a New York architect and author, said polls of Americans born before 1976 had revealed evolving preferences in urban living.

"It used to be that the most desirable place was the penthouse," he said. Now, with the growth of projects incorporating retail, restaurants and entertainment venues among high-density housing, Generation Y's preference is to be on street level, "amid the action," Kliment said.

* Outdoors in, indoors out. More Americans continue to want their living rooms to have the openness and serenity of a garden, and their gardens to be as furnished and decorated as a living room.

* Smaller but better. Several architects expressed hope that the smaller-is-better movement, popularized by "The Not So Big House" author Sarah Susanka and others, may finally be gaining traction. Duo Dickinson, a Connecticut-based architect and author, likened mega-size homes to the Hummer sport-utility vehicle in explaining what he saw as a paradigm shift. Dickinson said the vehicles at one point gained cachet as a status symbol, but some people now see those SUV buyers as overly image-conscious followers of a fad.

"People have been much more interested in smaller homes of a much higher quality, with a high level of fit and finish," said speaker John Senhauser, a Cincinnati architect.

The growth of immigrant populations and the diversity of living arrangements mean that families' needs are more varied than ever. The small-house movement notwithstanding, the prevailing wisdom is that square footage -- not good design -- remains the only feature to ensure a home's high resale value, Dickinson said.