Although large population trends, such as the skyrocketing number of seniors in the United States, grab a lot of attention, the nation is also on the cusp of a smaller demographic boom. Between 2000 and 2008 the rate of autism diagnoses increased dramatically, up from 1 in 150 children to 1 in 88. Over the next decade, about 500,000 children with autism will reach adulthood, with no clear path to managing their lives on their own. “There's not a solution for where they're going to live long-term when their families are no longer able to take care of them,” says Marsha Maytum, principal of Leddy Maytum Stacy Architects (LMS).

In 2009, a group of parents and autism professionals began working on this problem. They formed a nonprofit, Sweetwater Spectrum, and bought a 2.8-acre urban infill site just off the old town square in Sonoma, California. The board of directors brought on LMS to conceive a new housing model grounded in the latest research. In addition to specific requirements—such as a legible, repetition-based site layout and interiors that reduce sensory stimulation—the board and the design team started with the premise that adults with autism should have the opportunity for self-determination.

The Sweetwater Spectrum residential community, which opened in January, consists of four single-story, 3,250-square-foot homes with four single bedrooms each, as well as a community center with a gym and teaching kitchen, a therapy pool, a greenhouse, an orchard, and a small organic farm. With its homey, wood-frame structures clad in fiber-cement-board panels and accented in red cedar, the campus is not a hospital or even a social program: it is strictly housing. Sweetwater CEO Deirdre Sheerin likens the project to a retirement community with social activities. Residents still receive services—a few require round-the-clock supervision, for instance—but their families are the ones who coordinate their care, through state or private funding.

Autism is not a single disorder. But many on the spectrum share characteristics, such as a need for predictability and trouble with social interaction. LMS addressed these concerns by organizing the campus's shed- and flat-roofed structures as a grid of nested spaces that gradually become more public. Private bedroom suites open to hallways; two suite pairs surround a living room and kitchen to form a house. Outside, the houses form pairs and then a foursome around the pool and community center. And at each entry point into a more social area, there is a protected pause—under a canopy, perhaps, or at a shielded bench or patio—so residents can assess their options before they engage, explains Maytum.

The nesting pattern also finds expression in Sweetwater's position in the wider community, where some residents hold jobs and everyone ventures out for activities such as walks and bike rides. “One purpose of Sweetwater is to push toward normalcy and give choices,” says Sheerin.

For the houses, the architects chose a palette of subdued colors and durable materials such as carpet tile, linoleum, and high-density gypsum board. They prioritized indoor air quality and indirect lighting because many adults with autism have sensory sensitivities. Ambient sounds are softened with perforated wood ceilings and a low-velocity ventilation system that incorporates radiant heating and cooling. (Ceiling fans were avoided because their rapid motion and flickering shadows can cause discomfort.)

Since Sweetwater was conceived as permanent housing, LMS built in accessible features: wide corridors, low countertops, and wheelchair-friendly bathrooms, for instance. “The plan is that residents will age in place,” says Maytum.

The architects also looked ahead to 2020—California's target date for achieving net zero energy for all new residential construction. Rooftop solar panels, which supply about 72,000 kilowatt-hours per year, satisfy about 75 percent of the campus's energy needs; additional panels, if installed later, would bring the project to net zero.

But the project's largest ambition lies in the social ties its creators hope will take root, both among residents and between Sweetwater and the town. Residents who participate in the farm, for example, might gradually form friendships. And at harvest time, townspeople may gain some familiarity with autism through Sweetwater's roadside farmstand. “One of our responsibilities is to be educators to the community,” says Sheerin, adding, “Autism is, and will continue to be, very much a part of our culture.”

Size: 16,315 square feet (gross)

Cost: withheld

Completion date: January 2013

Lamar Anderson is a San Francisco–based writer and a frequent contributor to RECORD.