(Rich Schultz/THE ASSOCIATED PRESS)

Perhaps you know about “aging in place” and the community-based “village” movement organized to provide support for elderly people who want to remain in the old neighborhood rather than relocating to an assisted-living facility.

Now there’s a relatively new term: “NORC,” for naturally occurring retirement community. A NORC is a community where aging in place occurs organically.

These terms reflect the evolving character of residential neighborhoods affected by an increasingly significant demographic change: ever more senior citizens.

[The Washington area is seeing an explosion in the construction of “active adult" developments for people 55 and older, coming up in Saturday’s Real Estate section.]

Thanks to improved health care and better behavior, older Americans are living longer. Today’s younger Americans are likely to live even longer. Thus, America’s aging population is not only growing substantially but the aging are also staying put and increasingly reshaping urban and suburban development.

NORC residents are aging in place despite owning a home larger than they need; despite the cost and inconvenience associated with continual home upkeep and maintenance they would just as soon avoid; and despite coping with winter weather year after year.

What motivates this?

Strong attachments to a community are among the most powerful incentives for aging residents to stay in a neighborhood and stick with what they know, like and love: family, friends, familiar places, known travel routes and favored destinations. Moving elsewhere means leaving all that behind and starting from scratch somewhere new and different.

Some aging homeowners are strongly attached to a home because it’s beautiful to inhabit, use and look at. Particular aesthetic and functional qualities may seem difficult or impossible to replicate. The attachment may stem, in part, from a desire to maintain unoccupied bedrooms and sizable living spaces to accommodate periodic visitors, especially children and grandchildren, and for entertaining. Yards and gardens around a house, plus views and vistas from the house, may reinforce its enduring residential allure.

Spend decades living in one home, and you are likely to have filled it with furniture, collectibles and other contents to which your attachment is strong. Moving elsewhere typically necessitates getting rid of stuff and always entails making painful choices about what to keep and what to sell or give away.

Strong emotional attachments to a home and its contents translate into an unwillingness to downsize, no matter how practical and ultimately necessary downsizing may be. Resistance to downsizing keeps many aging homeowners from moving, as do the cost and hassle of moving. Like death and taxes, moving is at the top of the list of things people would rather not face.

The challenge of selling a house at an acceptable price can also motivate aging in place. If the local real estate market is soft, if home values are static or falling, selling a mortgaged home can be problematic. Homeowners may decide, for financial reasons, not to sell and to age in place if selling would yield little or no equity, or result in a loss, after paying off the mortgage.

Incentives for NORC formation intensify if aging homeowners are unable to find acceptable housing alternatives. In Washington, dwelling options — especially apartments — that satisfy the needs of many retirees are scarce. These older folks are dissatisfied because so many recently built apartments are too small, and prevailing condo prices and apartment rental rates are too high.

The village movement, aging-in-place and NORC phenomena inevitably will affect American cities and suburbs.

Ever more older residents in neighborhoods and communities will mean fewer school-age children and diminished school enrollment pressure. Retirees drive less or stop driving; many will walk more. This will reduce traffic and parking demand while upping the need for transit options and pedestrian-friendly streetscapes.

NORC residents will expect more pedestrian-accessible, convenience-shopping opportunities, especially in suburban areas where buying a quart of milk or a bottle of aspirin often requires driving several miles.

All NORC housing, commercial and civic buildings, and public parks will need to be accessible to accommodate people with physical impairments. And demand for outpatient health-care facilities, especially clinics, will rise.

In the Washington area, this demographic trend will pose economic and marketing challenges for housing developers who target younger, high-earners in urban areas and relatively affluent families in suburban areas. Especially difficult, whatever the area, will be making new housing affordable for aging retirees with limited assets and incomes.

Suitably housing aging occupants in NORCs poses another challenge: retrofitting non-accessible urban and suburban homes built decades ago. To provide adequate comfort, safety and mobility, various elements of older homes — stairs, railings, hallways, kitchens, bathrooms, built-in cabinetry — usually require some modification.

Fortunately, a longtime homeowner’s built-up equity can make financing retrofits relatively easy, especially costly ones such as kitchen and bathroom makeovers or stair-climbing elevators.

And a multi-generational NORC can provide another benefit: a ready supply of babysitters for children whose parents and grandparents live in the same community. NORCs promise to become a communal, 21st-century version of the extended family.

Roger K. Lewis is a practicing architect, a professor emeritus of architecture at the University of Maryland and a regular guest commentator on WAMU’s “The Kojo Nnamdi Show.”