It already had four floors of living space, but he wanted to make it even bigger and add an elevator and other modern luxuries, leaving little intact behind the red brick facade.

His plan set off the latest battle over the character of some of New York City’s most expensive neighborhoods, pitting affluent buyers who believe they have every right to remake the urban landscape, just as others have done for generations, against preservationists who contend that things have gone too far.

In the Chelsea neighborhood, where the row house sits, residents banded together in protest, fearing that they were being targeted by a wave of speculation that would turn some of the oldest houses in the city into much larger, modern mansions for wealthy interlopers.

They had already lost one fight.

A local community board had tried in vain to stop a similar expansion just seven doors away, in a home that is considered the oldest dwelling in Chelsea.

But in this second case they prevailed: The city’s Landmarks Preservation Commission, which is charged with protecting significant buildings, rejected the expansion of the home on West 20th Street as too “overwhelming” for neighbors.

The new owner, David Lesser, a Long Island-based real estate investor, did not respond to requests for comment.

The clashes in Chelsea are symbolic of a widening rift in the city between everyday residents and developers looking to create luxurious enclaves that only the elite can afford.

“The history of real estate in New York is all about speculative construction,” said Andrew Dolkart, a professor of historic preservation at Columbia University. “But I have always felt that what makes a dynamic city is the mix of the old and the new.”

David Holowka, a retired architect who led the opposition in Chelsea, worried that the block could become another “billionaire’s row” — the nickname for the ultraexpensive apartment towers sprouting near Central Park.

Sandwiched between Greenwich Village and the new Hudson Yards mega-development, Chelsea had long been a diverse neighborhood filled with working-class and middle-class residents. But it has gentrified rapidly in the decade since the High Line elevated railway was transformed into a public park — now a top tourist draw.

Google, which already has a large footprint in the neighborhood, has been buying more buildings as it continues to expand its East Coast base of operations.

But Holowka said he does not believe Google employees are the ones interested in Chelsea’s row houses.

“They’re probably the sorts of owners who own condos along the High Line,” he said, implying a spending spree by wealthy buyers who do not live in the neighborhood.

The average price of condominiums sold in Chelsea last year was $2.9 million — a figure that doubled in the past decade, according to a real estate analysis.

Jonathan Miller, the author of an annual survey of the town house market, said the median price of town houses in Manhattan was $5.2 million last year, five times the median price of an apartment in the borough.

Miller said it was inevitable that people who could afford historic houses would want to do a “gut rehab” to bring them up to modern standards of luxury.

“Because they’re much more expensive in general, they’re attracting a higher-end buyer,” he said. “That higher-end buyer is going to want something that’s new but looks like a landmarked town house.”

One recent overhaul of a vintage row house that alarmed the neighborhood’s preservationists occurred on West 22nd Street, next to Clement Clarke Moore Park. The park is named for the author of the poem commonly known as “’Twas the Night Before Christmas,” who once owned an estate that took up much of what is now Chelsea.

A couple, Bill White and Bryan Eure, bought the house for $4.6 million in 2012 and turned it into a showplace that was featured in Architectural Digest. They equipped the 5,000-square-foot house with a basement entertainment/media center and a roof terrace with an outdoor shower and whirlpool tub.

Then they sold it in 2014 for more than $16 million to a Mexican tortilla heiress. The lucrative overhaul of that property spurred concerns of widespread speculation in the Chelsea Historic District, several landmarked blocks that surround the General Theological Seminary of the Episcopal Church.

“The big threat,” Holowka said, “comes partly from the High Line and partly from billionaire investors.”

But Eure said such fears were overblown.

“Some people oppose change no matter what, and when these homes collapse because no one cares for them, everyone loses,” he said.

The plan for renovating the neighborhood’s oldest house, at 404 W. 20th St., sparked an even bigger outcry. Most tours of Chelsea start at the northeast corner of that house, where its original clapboard siding is visible along a narrow alleyway that leads to its backyard. The house, which has a brick front wall and about 4,000 square feet of living space, was built in 1830 on a lot leased from Moore.

An investor, Ajoy Kapoor, who bought the house for more than $7 million four years ago, proposed an overhaul that the local community board said would have extended the rear wall into the yard and added two upper floors and a cellar level, doubling the living space.

In a 2016 letter to the preservation commission, the community board objected that Kapoor was proposing “to demolish the entire house except for its brick street facade.” The board pleaded with the commission to uphold its mission “to protect our shared historic legacy from destructive market forces of the kind now at a fever pitch in Chelsea.”

Over the community board’s unanimous pleading, the commission blessed Kapoor’s expansion plans.

A spokeswoman for the commission explained in a statement that its role “is not to prevent change but to ensure changes are appropriate to the character and style” of landmarked buildings and historic districts.

Preservationists in Chelsea, like Pamela Wolff, were devastated.

“It was a massive battle that we lost, bitterly lost,” she said.

Preservationists feared that it would set a precedent for investors seeking to turn a quick profit by buying up the neighborhood’s old buildings and turning them into sprawling new homes with false fronts, Holowka said.

“The facade is supposed to tell you something honest about what’s inside,” he said, adding that overhauled mansions would be affordable only to people who might spend little time actually living in them.

Wolff said the commission had accepted “facadism,” the view that as long as the face of a historic building is preserved, it is permissible to tear down the other walls and create a much bigger structure.

In the three years since the commission’s decision, the old house has stood empty, although a brass plaque on the front wall identifying it as the oldest dwelling in Chelsea has been removed. Kapoor, who runs an investment firm in London, did not respond to requests for comment.

In the meantime, Lesser bought a house on the same block, at 418 W. 20th St., for close to $8 million. It is part of a set of seven Greek Revival homes built in 1840 that are known as Cushman Row.

Lesser proposed expanding the house by pushing the rear walls back as much as 10 feet and adding a subbasement. Plans presented to the preservation commission show a master bath with a fireplace.

The community board again unanimously objected to the plan, saying in a letter to the commission: “It is difficult to understand how a 5,500-square-foot single-family house isn’t already big enough and why an individual owner’s desire for surplus space should outweigh the value to the public of an intact major landmark.”

This time, the commission agreed. In a 6-0 vote, it denied most of the changes the new owner had proposed, saying they would diminish the unity of the seven houses that make up Cushman Row.

For now, the Chelsea residents who have fought to preserve the neighborhood’s homes are celebrating their successful campaign, although they are anticipating more battles.

“This has the potential,” Wolff said, “to really turn the whole facadism thing around.”