Freddie Gershon lives with his wife, Myrna, and his dog in a penthouse duplex with a terrace in Midtown East. The space is plenty big, he concedes — 6,500 square feet.

But apparently not quite big enough. Last month, Mr. Gershon, the chief executive of Music Theatre International, a licensing agency, closed on some additional real estate in his co-op: a one-bedroom 1,000-square-foot unit on the fourth floor.

“I have reached a point in my life where I want to write,” he said. “I have a book in mind, and I wanted a sanctuary that didn’t require me to get dressed and go outside. I wanted to go to the passenger or service elevator and just go to a different floor.”

Mr. Gershon said he had tried working at home. “But then I’d hear the phones,” he said. “Or I’d get distracted by the view of the river.”

New Yorkers who need more space, but would rather not move, generally try to make a deal with the departing next-door neighbor — oh, for a departing next-door neighbor — or with the people who live directly above or below. Deal done, they get busy punching through walls and ceilings to combine their holdings into a single flowing residence.

But some, like Mr. Gershon, while they are eager for more room, really don’t want that room to be right in the next room. They’d prefer something that’s an elevator ride or a few flights of stairs removed from the mother ship. A noncontiguous apartment — typically, a studio or a one-bedroom — whether used as a writing or an art studio, an office, a man-cave or an escape hatch, allows its owners or renters to be so near and yet so far.

This form of branching out may be happening a bit more these days because the market is improving, making potential buyers less skittish. It also helps that inventory for these smaller apartments is deeper than for larger units.

“I tend to observe this pattern when, like now, markets are ticking upward,” said Jonathan J. Miller, the president of the real estate appraisal firm Miller Samuel. “People are more aggressive in asserting their own quirks, more confident. It’s almost a whimsical purchase. It’s like: ‘Oh, there’s a one-bedroom for sale on the fifth floor. Maybe we should buy it,’ ” he said. “It’s a way to enhance the enjoyment of living in a particular building.”

In some prewar buildings where maids’ rooms were laid out on a separate floor, Mr. Miller said, “people buy them and turn them into a study or additional storage space or me-time rooms.” In one co-op on East End Avenue, he came across “side-by-side maids’ rooms combined and made into a private gym for a resident, with a shower and a wine cellar.”

But, as he points out, the person who buys or rents a noncontiguous apartment isn’t doing so to have more “walking-around” terrain. This is space meant to serve a discrete function, to help fulfill a specific fantasy: writing the Great American Novel, for example, or sculpturing a masterpiece — activities that, given all the usual interruptions, would be impossible to engage in at home.

And unlike most real estate fantasies, it doesn’t command a premium. “Let’s say you have a 1,500-square-foot apartment on the seventh floor and buy a 500-square-foot studio on the third floor,” Mr. Miller said. “The aggregate total of noncontiguous studio plus original apartment would be a lot less costly than buying a 2,000-square-foot unit.”

That is, if you could even find a 2,000 square-foot unit. “There are now twice as many studios and one-bedrooms available in Manhattan as there are three or more bedrooms,” said Beth Fisher, a senior managing director of the Corcoran Sunshine Marketing Group. “The ultratight market is forcing buyers to request combinations or seek out noncontiguous apartments.”

Six months ago, soon after their twins were born, Catherine and William Ebert bought the 300-square-foot studio across the hall from their three-bedroom co-op on the Upper West Side.

“It had come on the market and I thought, ‘Wouldn’t this be so great,’ because I work at home, and with the twins that’s hard to do,” said Ms. Ebert, an interior designer. “I’d be close by, but I could have some peace and quiet and get stuff done and not be bothered.” Her husband, a lawyer, was also looking forward to having a place to do a couple of hours of work without having to repair to the office.

Combinable apartments would have been preferable, Ms. Ebert said. “But it’s so handy the way it is. We have filled the studio with all sorts of storage stuff. I keep the car seats there and an extra crib. They’re not cluttering up our house, which is nice. If the apartments were connected, the mess would be more bothersome.”

For years, Anne Adams, an author, rented an office 20 minutes’ walk from her two-bedroom duplex in a Park Slope co-op. “I loved it,” she said. “But it wasn’t convenient. If the weather was inclement I would find reasons not to go.”

So when the garden apartment in her building became available, the pieces fell nicely into place. “It’s great to have a place that’s separate from where you brush your teeth,” Ms. Adams said. “When the phone rings, you know it’s work-related. If the doorbell rings, you can answer it or not.”

She has used the space to conduct interviews, work on book collaborations and entertain friends. “My daughter would host sleepovers there when she was an adolescent,” she said. “And when she graduated from college she stayed there. It was a good transitional thing for her.”

When Michael Sorrentino began living with his girlfriend, Caroline Bass, in her Upper West Side rental in early 2012 — they were married last October — Ms. Bass, an associate broker at Citi Habitats, was worried. Their love was here to stay for sure; so, alas, was her fiancé’s soundboard, to say nothing of his six guitars and three amplifiers. Mr. Sorrentino, an executive at Citi Habitats, plays in a rock band.

“There was no way that would all fit into my one-bedroom apartment,” Ms. Bass said. “We thought we would have to get a bigger place.”

But a few months later, the next-door neighbor decamped to live with his girlfriend, and Ms. Bass and Mr. Sorrentino rented his 250-square-foot studio. “So now Mike has all his guitars there,” Ms. Bass said. “If he wants to play them for three hours, he can and not be interrupted. He’s got his TV there. He has his friends over to watch football.”

The couple considered asking the landlord’s permission to knock down the wall between the units, said Ms. Bass, who had some second thoughts. “I was like: ‘What do you mean you’re going to have this separate place? How much time are you going to be spending there?’ But it’s turned out to be the best thing.”

Some buildings, co-ops in particular, may be less than enthusiastic about residents’ owning more than one apartment on the premises.

One couple in Riverdale learned this recently when they decided to buy a one-bedroom unit in their building so the husband, recently retired, could pursue a lifelong love of painting and calligraphy. Their broker, Lee Moskof, an agent at Halstead Property, recalled that the co-op board “made my clients go through a very intensive application process even though it was an all-cash sale.”

She said the concern was that because the apartment would be used as an art studio, the public might be invited in for exhibitions. “The board didn’t want that to happen,” Ms. Moskof said. “There was a lot of Sturm und Drang, but he finally prevailed.”

According to Aaron Shmulewitz, who heads the co-op and condo practice at the law firm Belkin Burden Wenig & Goldman, the reluctance of co-op boards to approve such transactions stems from concerns that a noncontiguous apartment could be used for a commercial enterprise like a bed-and-breakfast.

“And when they do approve them,” Mr. Shmulewitz said, “they impose all sorts of restrictions, primarily that it will only be used as a writing studio or an office and that there won’t be overnight guests in the apartment more than X times a year.”

There are other legal issues to consider, according to Steven R. Wagner, a real estate lawyer at Porzio, Bromberg & Newman. “These buildings are zoned residential,” he said. “If the space is being used strictly for business purposes, it may be a zoning violation or a violation of the certificate of occupancy.”

To reassure boards, he added, buyers should describe the second unit as additional living space and make sure the apartment remains usable as living space by keeping the kitchen intact.

The studio the Eberts bought gives them welcome flexibility: office today, something else tomorrow. “Maybe a little down the road,” Ms. Ebert said, “it might make sense to have it be the playroom and for me to move my office back to our main apartment, because then the mess and toys will be out of sight.”

Meanwhile, she said, she and her husband teasingly speculate about their baby twins’ taking up full-time residence across the hall: “We keep joking about what would be the right age for them to have the studio as their home.”