Two years ago, while walking his family’s new puppy, Paul Boardman had the kind of epiphany only a real estate entrepreneur can have.
A developer who was once the lead designer for all the Equinox gyms, Mr. Boardman was passing by 711 West End Avenue in Manhattan, a seven-story apartment building of red brick and squat windows between 94th and 95th Streets that looked almost as if it were shrinking from the grand prewar buildings around it that are twice its size.
Mr. Boardman envisioned something equal in stature for the site. But tearing down 711 West End Avenue would be all but impossible, considering that most of its 144 apartments are rent-stabilized, giving their tenants a right to stay.
So Mr. Boardman came up with a daring plan. By threading a series of multi-ton support columns around the existing structure, a new 10-story condominium tower could be built. It would essentially sit not atop the old building, but above it, with its bottom floor hovering more than 80 feet in the air.
“We get to unlock the value of this site and create a building truly worthy of this great neighborhood without displacing any of the existing residents,” Mr. Boardman said in an interview last week.
In a city where the only place to go is often up, adding floors to an existing building is nothing new. Rarely, if ever, is this work undertaken over an occupied apartment building. If it works, though, other developers might start stacking apartments, too.
“The idea is genius,” said Jesse M. Keenan, research director at the Center for Urban Real Estate at Columbia University. “The execution will be challenging, but not impossible.”
The soon-to-be downstairs neighbors are not so enthusiastic. Tenants in about half of the apartments at 711 West End Avenue have formed a group opposing the project, contending that the blueprints do not begin to convey what the project will look and feel like from below.
“I’m afraid for my life that any minute, one of these three-ton steel beams could come crashing through my wall,” Stephanie Cooper, a resident of 47 years, said last week inside her two-bedroom apartment on the fourth floor. She originally paid $267 a month, and now pays less than $2,000.
While building a 10-story building over a seven-story one might seem like a futuristic proposition, the engineering for 711 West End Avenue is quite conventional, certainly when compared with all the cantilevered building extensions and 1,000-foot-tall but 50-foot-wide towers on the horizon.
Here, the top 10 floors will sit on a steel and concrete platform supported by a crisscrossing steel superstructure surrounding but not touching the lower building. Other than the shaft for a new elevator and fire stairs that will run from the lobby to the new eighth floor, the buildings are totally separate. A roughly six-foot gap will separate the roof of the existing 1952 building and the bottom of the new one because they must comply with different fire codes, though the facade of the Art Deco-inspired addition will obscure the gap. The idea is to unify the buildings visually but not physically.
“We hired all the best consultants, and it’s pretty amazing what they’ve come up with,” Mr. Boardman said. He is teaming up with the Miller family, which has owned 711 West End Avenue since the 1960s, and SJP Properties, a large New Jersey developer.
Some of the Millers even live in the building, as do two of Mr. Boardman’s relatives who recently moved in. The owners point to this as proof they will take the utmost care during construction.
Those in the tenants’ group remain suspicious. They say they are worried not only about the risks posed by two or more years of construction above them, but also the continuing impact after the building is finished, such as how the new steel structure might overshadow their windows.
The group hired its own engineer to challenge the developer’s tenant safety plan, arguing it is insufficient. And the boards of the neighboring co-op buildings and parents at Public School 75 across 95th Street have joined with Councilwoman Helen Rosenthal to oppose the project, calling it a danger to surrounding properties.
Even so, the city’s Department of Buildings approved permits for the project in June, though it did subject the plan to additional scrutiny, including a review by its high-rise investigations team and an independent engineer. The department has tried to reassure residents the new building will be safe. “It’s our mission to facilitate safe development,” Thomas Fariello, the department’s first deputy commissioner, said in an interview. “Notice that safety comes before development.”
The owners maintain that the project will be a boon for current residents as well as new ones, and not only because they get to stay. The plans also call for adding new windows and central air-conditioning to all existing units, as well as a new lobby and a courtyard garden.
Yet even these plans are seen as intrusive by some.
“This isn’t for the tenants; it’s for them,” said Barbara Stark, who has been there 52 years and has seen four generations grow up there, including her 16-month-old great-granddaughter. “They just want it to look nicer so they can sell their condos.”
While the renovations have been held up as a benefit, they could also be used to raise rents for stabilized tenants through capital improvement charges.
“This is not an end-run scheme of any sort,” Edward Kalikow, the building manager, said. “If anything, it’s going to enhance the value of the asset for everyone there.” He said that if tenants cooperated, the owners would consider not raising the rent for improvements.
The work will no doubt be disruptive for residents. For construction to proceed without dislocating tenants below, their building will be shrouded in reinforced scaffolding, and they could experience noise and vibrations. And anyone who does not allow access to their units for work could be threatened with eviction.
An eviction case is already underway for a seventh-floor tenant who lives where the new elevator is planned. She is the only one in that vertical column of apartments who has not accepted a buyout and moved out or to another apartment. Neither the tenant nor her lawyer responded to requests for comment.
Mr. Boardman said there were three alternatives to build around her, if need be, so she could not stop the project.
And though they have not been as vocal as their neighbors, some residents said they were actually looking forward to the expected improvements. One tenant of two years, Zoran Nikolin, sounded unbothered by the coming work.
“It’s going to be great for everybody,” Mr. Nikolin said. “But we have to endure the nuisances for that to happen.”
An earlier version of this article erroneously stated a disruption related to the construction of a condominium building. Residents of the sixth and seventh floors in an existing building will not have to be temporary relocated; the developer said that it is working on a plan that would avoid those residents having to move.