They never wanted to call it retirement, but for Susan Farnsworth, Leigh Hough and Jean-Philippe Jomini, a throuple — a romantic partnership of three people — that has lived together as an intentional family for more than 15 years, it felt important to get a head start on finding a home that would accommodate future needs for aging in place.

Three consultants in their mid-60s, they share a home in Fort Lauderdale, Fla., but decided a few years ago to look for a second home in southern New England, where they have friends and family.

A string of open houses and home tours turned up nothing truly satisfactory. So on a whim they checked out a “land for sale” sign during a day of driving around Guilford, Conn., and there it was: an unimproved 1.7-acre lot of restored tidal marsh that had the allure of ever-changing scenery, natural light and an array of wildlife.

They purchased the land for $320,000 in the summer of 2016. When it came to design, a few things were nonnegotiable: enough privacy to allow for plenty of windows, tidal marsh views and an easily maintained home and yard that would also be eco-friendly.

Their individual wishes became diplomatic discussions — was there room for a workshop for woodworking and gardening needs? How about a kitchen garden? These made the cut, as did a small salt-chlorinated pool. But being able to live comfortably there as they grew older together was their primary concern.

“This is the first time we have worked for a three-­person couple for whom gracious aging — of materials and occupants — was part of the discussion from the outset,” said Rustam Mehta, a founding partner of GRT Architects, the New York firm that designed the 3,300-square-foot house.

The one-story house embodies universal design principles that are also senior-friendly, such as versatile open spaces, minimal stairs and wider doorways and hallways. The three- bedroom home is also wheelchair-­accessible and barrier-free — there are no steps or thresholds across the entire principal floor. And there’s not a tub in sight: All three bathrooms feature zero­-threshold showers.

For the country’s swiftly growing older population, this safety-­focused attention to detail is essential to healthy home life. More often than not, changes are hurriedly made in response to a fall, accident or medical diagnosis. The website for the Centers for Disease Control and Prevention shows that for adults 65 and older, $50 billion is spent annually on medical costs related to nonfatal fall injuries, and $754 million is spent related to fatal falls.

As baby boomers born between 1946 and 1964 continue to age, the U.S. Census Bureau predicts that people over the age of 65 will outnumber those under the age of 18 as soon as 2034. To address the needs of this rapidly growing population, AARP encourages its members to carefully consider ways to make their homes places where they can comfortably and safely age in place.

These kinds of upgrades can start with simple things like installing task lighting in kitchens to accommodate fading eyesight and multiheight countertops to allow people of all abilities to both stand and sit while working in the kitchen, investing in nonslip tiles and grab bars in bathrooms, and relocating select electrical outlets to be 18 to 24 inches high, up from the more typical 12 inches off the floor, to make them more accessible. Bigger changes can include enlarged doorways to allow for wheelchair access or a walker, and ramps to eliminate stairs.

AARP recently introduced HomeFit, a free augmented-reality app on iOS that can scan a room and suggest improvements to help turn a house into a “lifelong home,” free of safety and mobility risks. It is an extension of the organization’s extensive HomeFit Guide, available online.

There are also certified aging-in-place specialists, a wide range of professionals including remodelers, designers, architects and occupational therapists, who can recommend modifications to help people live independently in their home. This designation was developed in 2002 by the National Association of Home Builders in collaboration with AARP and other experts. Specialists can be searched by state at nahb.org, which offers a three-day certification program.

Even the smallest safety updates can potentially be lifesaving.

Ted Porter, a co-chairman for the Design for Aging Committee for the New York City chapter of the American Institute of Architects, said making an apartment or home aging-friendly can be relatively easy, inexpensive and done gradually over time.

Simple upgrades include professionally installing grab bars along long corridors and replacing toggle light switches with glow-in-the-dark rocker switches that are easier to turn on and off.

Porter also suggests increasing the output of available electric light sources by using larger-wattage or lumen bulbs and recommends contrast between wall and floor colors, and between floor hues or finishes wherever height levels change.

For some families, retrofitting an existing home isn’t a viable solution, so they have turned to accessory dwelling units, or ADUs. Often called a “backyard cottage,” they are one way to facilitate multigenerational living on the same lot.

For Alice Savage, 74, a retired college professor and dean, a one-bedroom ADU in the backyard of her daughter’s home in Portland, Ore., became even more of a haven when she received a cancer diagnosis in January.

Its cozy, manageable size has been a blessing, Savage said of her single-story 576- square-foot home, which was completed in late 2016 by Environs, a local design-build company. A stepless front entry and a concrete walkway sloped to the sidewalk allows easy passage between indoor and outdoor spaces. A shared outdoor courtyard connects her home to the one where her daughter, Megan Savage, and son-in-law, Rick Freed, live.

Although she had downsized from a larger condo to the ADU, it did not mean there was any skimping on personal preferences.

“I wanted a ‘real’ full kitchen and a small area for a desk. I wanted lots of natural light, crucial in Portland in winter, and ended up with three skylights plus good windows,” said Alice Savage, who spent about $125,000 on the home.

The bedroom is moderately sized with a long closet, and the bathroom, purposely large at 11 by 7 feet, features a curbless shower, grab bars and a shower head with detachable hand-held sprayer that can be used sitting or standing.

There’s also ample room between fixtures for a walker or wheelchair, should they become necessary. Interior pocket doors are one space-saving measure and also create wider doorways in an instant.