Major renovations on aging buildings require delicate structural work, particularly when developers add floors, cantilever new sections or redistribute loads through an existing frame.
Structural engineers say those projects demand extensive analysis to ensure existing structures can safely support new weight and altered load paths. When something is overlooked in the design, engineering or construction process, the consequences can be severe.
“There’s a lot of structural analysis that has to go on. If that goes on carefully, everything should work out the way the engineers planned it,” said real estate attorney and structural engineering expert Barry LePatner. “If they fail to factor in certain things, or a column is taken out prematurely, it can have a major impact.”
Those engineering challenges were on display Tuesday at Metro Loft and David Werner Real Estate Investments’ conversion of the former Pfizer headquarters on East 42nd Street, where support columns buckled and several upper floors were sagging on an 11-story cantilevered addition to the original building, according to city officials.
Office-to-residential conversions, which have accelerated since the pandemic, typically require major surgery on older, outdated buildings to make them liveable. But structural engineering experts said there is no evidence that suggests the incident was caused by the office-to-residential conversion itself.
“The office-to-residential conversion project type, that in itself has nothing to do with what happened there,” said one structural engineer who has worked on multiple Manhattan conversion projects. “Clearly, something that should have been reinforced for the extra weight was not.”
There are currently 44 projects under way, nearly all of them concentrated in Manhattan, according to a 2025 report from the New York City Comptroller.
Based on images released after the incident, the engineer said it appeared that one of the original 1960 building’s steel i-beam columns had been reinforced with welded steel plates while another may not have been strengthened at all.
“This is just a mistake that happened, an engineering issue,” said the engineer, who requested anonymity because he knows multiple people working on the project. “It’s possible that the engineer did identify it to be reinforced, and it was not. Until someone goes through and reviews the drawings, we don’t know.”
The Pfizer project will transform two connected office buildings into more than 1,600 apartments. Plans call for recladding the existing 33-story tower at 235 East 42nd Street, carving out an interior courtyard and redistributing floor area to expand the building to 37 stories, according to Department of Buildings filings.
The project carves a new interior courtyard into the building to bring light and air to apartments on the lower floors, aligning with a courtyard at the neighboring 219 East 42nd Street, where the developers are adding 19 stories to the nine-story building, built in 1909, DOB filings show.
The damage appears to be confined to the new section of the larger building rather than the entire tower, the structural engineer said, adding that temporary supports should stabilize it if movement has stopped.
At a press conference on Wednesday, Mayor Zohran Mamdani said crews have installed temporary shoring and beams on floors 18 through 23, with additional supports scheduled to be installed from floors 9 through 37 throughout the day. He added that there has been no additional movement since Tuesday morning.
“I’m sure they’re monitoring it 24/7,” the engineer said. “As long as there’s no indication that it’s moving further, then it’s probably stable, and it’s probably safe, and they will quickly get the supports in to stabilize everything.”
The biggest unknown may be whether other parts of the building were damaged. The sagging floors appear to have shifted part of the curtain wall, he said, so engineers will need to determine whether the façade, windows and mechanical systems in that area were compromised.
An investigation will ultimately determine what went wrong. Determining the root cause could take weeks or months, particularly if the DOB orders an independent third-party review, experts said. Lawsuits and insurance claims could also complicate the process.
“That’s the big question. I would guess the lawyers are all circling right now. I’m sure the claims are going to come fast and furious, and then the insurance companies get involved,” the engineer said. “It’s probably in everyone’s interest to make it move very quickly.
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