ELLIE SALMAGGI, a medical secretary, reared four children in a two-story Dutch colonial in Water Mill. And when the four, now ages 29 to 37, had all flown the coop, Ms. Salmaggi wanted to downsize.

Older friends advised her to do herself a favor and avoid a place with stairs, and she concurred. She could see what a chore it was for her parents, now in their late 80s, to climb the stairs when they came from New Hyde Park for overnight visits.

When her youngest daughter, Denise D’Angelo, took her to see two model homes in a new subdivision on the North Fork called the Woods @ Aquebogue, Ms. Salmaggi loved the 1,850-square-foot three-bedroom ranch-style house. (Ms. D’Angelo, a teacher, opted for a 2,600-square-foot two-story model across the street in the seven-home subdivision.)

“As soon as I saw it I fell in love with it,” Ms. Salmaggi said of the ranch model. “I wanted something new and classy.”

She paid $444,000 for the construction of her single-story home, which has a cathedral ceiling in the living room and an acre of heavily wooded property.

As the population ages, builders, developers and brokers across the Island say they are noting an increase in requests for single-story homes, which have become harder to find as midcentury ranches, their looks no longer trendy, became teardowns over the years. Younger buyers, too, are finding themselves attracted by features like master bedrooms on the ground floor.

Pleased to be in a home that has the accessibility she may eventually need, Ms. Salmaggi, who arrived in July, also described the ranch as “easy to keep” and clean, adding, “It’s all I need right now.”

She has a roomy eat-in kitchen, three bedrooms and two full baths; the house is “perfect for entertaining,” she said, pointing out that the guest quarters are far from the master bedroom.

Jack Campo, a founder of Campo Brothers, a builder in Port Jefferson, said two of the seven homes at the Woods @ Aquebogue were ranches. The Meadows at Baiting Hollow, his 35-home subdivision, sold out in November. He built two ranch models there, and at least five buyers chose among one-story designs at three price levels: $399,990 for 1,850 square feet; $425,000 for 2,100 square feet; and $550,000 for 2,650 square feet.

“They are more popular now than they had been,” Mr. Campo said, while also explaining that because of the larger foundation and roof involved, such homes are more expensive to build than two-story residences. An 1,850-square-foot ranch, for example, cost the same to build as a 2,400-square-foot two-story colonial. “When you spread it out, everything costs more money.”

Twenty-five years ago, he recalled, 30 to 35 percent of the homes his company built were ranches. As colonials surged in popularity, “we got away from ranches,” he said. But then, a year and a half ago, “all of a sudden we got a call for them,” from empty nesters tired of stairs, who want to stay on the Island without opting for a retirement community.

Frank Campo, a principal in the family firm, said the new interest was causing a re-evaluation of company designs like the Meadowview, which was popular over two decades ago in Stony Brook, Setauket and Poquott. Its master bedroom is on the ground floor; two other bedrooms are upstairs. One of the firm’s new models, the Capeton, an updated Cape Cod, is similar to the Meadowview, with the first-floor master bedroom that most two-story homes lack.

In East Moriches, Mark Baisch, the owner of Landmark Properties, is selling ranches alongside colonials in a new subdivision of 17 homes.

“We are getting a lot of positive reaction” to the 1,900-square-foot ranch with two-car garage, Mr. Baisch said. “The big thing is to separate the master suite on one side of the house from the other two or three bedrooms,” using the living room, dining room and big open kitchen.

“The ranch is coming back,” he added. “People are looking to the future and realizing that the up-and-down on the staircase is not likeable for them.” In trying to avert “the senior condo route,” they are “willing to pay extra for the convenience of the ranch.”

Among aging housing stock, ranches can sometimes be hard to find. During the boom, builders snatched up ranches in areas like Jericho to knock down or convert to colonials, said Barbara Tomko, an associate broker with Shawn Elliott Luxury Homes and Estates.

At the Hamlet Estates in St. James, 12 of 127 homes sold have been ranches, said Rosanne Murray, the director of sales. The three models range from 3,239 to 4,000 square feet, and are priced from $709,900 to $1.04 million.

“We were expecting empty nesters,” Ms. Murray said, but preretirement-age people are buying them as well, drawn to the open floor plans.

Among them are Stephen DeMaio, a Port Jefferson pharmacist, and his wife, Suzanne, who went into contract on the smallest model in May. They said they liked the fact that the kitchen and family room were “one big room,” and that the dining room and master bedroom both had tray ceilings. “That reminded me a lot of the Florida-type homes,” Mr. DeMaio said, “and that was very attractive to us.” The couple are adding a basement and other extras that will bring the tab close to $1 million.

The DeMaios, who can still climb stairs “two at a time,” have two of three children living at home, so they won’t be empty nesters for five to six years. Still, they wanted “a change of pace” from the two-story contemporary that they recently sold after 18 years.

“My wife didn’t want to settle on a two-story,” Mr. DeMaio said, explaining that if she had still wanted to live in one, “she would have stayed where we were.”