Sylvia Denbo, 89, has spent 35 years "aging in place" at the Towers at Windsor Park in Cherry Hill.

Her neighbor Sue Rose, 93, has been at the towers for 25 years and needs a walker to get around. Barbara Haskel, 77, has lived there for 27 years.

Though the complex off Chapel Avenue is home to tenants from a range of ages, races and religions, its concentration of older adults qualifies it as a "naturally occurring retirement community" (NORC).

Jewish Family and Children's Services of Southern New Jersey has set up an on-site office, complete with nurse and social worker, to help older tenants of all faiths with their needs. Rose depends on the agency's in-house nurse to monitor her medical care.

Under the tenants' direction, the office, known as Cherry Hill Senior Life, organizes activities, including Wii bowling, an art-appreciation group, and a weekly dinner, that have transformed the towers into a haven for "people in their second childhood," jokes Harold Heine, 96.

NORCs with localized services are among many options - including shared housing for seniors, homes with in-law suites, elder-friendly interior design, and more hospitable outdoor environments - that municipal planners must consider as the proportion of elderly in the nation rapidly increases, say two local authorities on aging.

Between now and 2030, the number of Americans 65 years and older will double to more than 70 million, according to Delaware Valley Regional Planning Commission statistics.

"It's going to be scary when we have the state of Florida in all 50 states," said Jack Carman of Medford, owner of Design for Generations, which creates therapeutic gardens and landscapes for senior communities and health-care facilities.

Carman, a landscape architect, and his wife, Nancy, a gerontologist, are authors of the recently published Re-creating Neighborhoods for Successful Aging. Their collaborators are Pauline S. Abbott, director of the Institute of Gerontology at California State University, Fullerton, and Bob Scarfo, a landscape architect and social geographer at the University of Washington-Spokane.

"Our neighborhoods were created for people in their 20s and 30s," said Jack Carman. "They're for people who can fully function."

"A lot of seniors are 'overhoused' - still living in the four-bedroom house where they raised their families," said Peter Kasabach, executive director of the smart-growth group New Jersey Future.

Many struggle with yard work and housekeeping. Shopping, socializing and getting to doctors' offices become difficult when they no longer drive.

Some municipalities, including Collingswood, have incorporated senior housing into their "town center" makeovers, so older residents can downsize without leaving town, said Kasabach, former policy chief for the New Jersey Housing and Mortgage Finance Agency. A walkable downtown works for all ages, he said.

But others, such as Medford, the Carmans said, lack sidewalks and adequate lighting for walking or biking.

"You don't want people to become prisoners of their own homes," said Nancy Carman, director of marketing services for New Life Management & Development Inc. in Mount Laurel, a consultant on continuing-care retirement communities.

Most 55-and-older neighborhoods are designed for "active" adults, Jack Carman said. Homes have master bedrooms and bathrooms on the main floor, but they often have steps or doorways that are difficult to negotiate for those who use a walker or wheelchair.

Jennifer Weiss, executive director of Jewish Family Services, foresees two trends: Quality nursing homes will become harder to get into, and more people will choose to remain in their homes.

"Assisted living is almost passe," she said. "People want to own their own little piece of the world."

Developers couldn't build enough retirement complexes to accommodate the nation's aging boomers, anyway.

In the Philadelphia region, one in five residents will be over 65 in 2025, according to the regional planning commission.

In New Jersey, Burlington County will experience the most dramatic demographic shift, with the number of senior citizens climbing from 53,000 in 2000 to 107,000, the commission predicted. In Pennsylvania, Bucks and Chester Counties will see the largest increase in elderly.

In a down economy, many seniors cannot afford to relocate, the experts said.

Weiss said many of her clients are stuck in the middle - too wealthy for Medicaid but unable to pay the monthly fees at assisted-living and continuing-care facilities. That leaves them seeking other options.

The Carmans' book suggests communal elder residences or in-law suites, but many towns would need to amend their zoning regulations to permit such arrangements.

They also recommend builders follow universal design standards that incorporate ramps, handrails and wider doorways.

Outdoors, crosswalks should be wider and traffic lights should be calibrated to give slower-moving pedestrians time to cross the street, Jack Carman said. Older people are more likely to exercise on pathways that have shade and benches, he said.

"Our goal is to allow people to age gracefully, safely and independently in their homes," said Gail Belfer, director of senior services for Jewish Family Services. But "suburbia isn't set up for seniors," and services are hard to deliver, particularly for those who live far from population centers.

With the coming retirement boom, these issues may get the government attention they need "if louder voices get raised," Belfer said.