NEW YORK - The buckling of two steel columns this week at the former Pfizer headquarters in midtown Manhattan triggered evacuations and paused progress on one of the country's biggest office-to-apartment conversions.

The event also underscored the intricate engineering demands of adaptive reuse initiatives, which have grown more common as leaders seek to address a national housing shortfall by repurposing offices left largely empty after the COVID-19 pandemic.

The project aims to convert two office structures - one from 1909 and another from the 1960s - into roughly 1,600 apartments through the addition of over a dozen stories on the older building along with redesign and expansion of the second. The buckling took place on the 21st floor of the newer tower, where crews have added temporary supports while officials probe the cause.

Engineering specialists noted that the conversion involves significant complexity and multiple obstacles, such as verifying that older structures can bear new weights and dividing office spaces for residential use.

Yet none indicated that the notable incident should cast doubt on engineers' capacity to finish these efforts.

"I do not believe it truly questions our grasp of how to handle such work," said Ben Schafer, a structural engineering professor at Johns Hopkins University.

On its site detailing the midtown effort, adaptive reuse company Collaborative Construction Management notes that the nine-story structure from 1909 will be "threaded through" with a fresh addition of about 30 stories of poured concrete.

Schafer, uninvolved in the project, explained that the probable method keeps the old building supporting its own weight while a new system handles the additions.

"My view is that they will keep that building bearing its own load, and they will simply create openings so the weight from the new upper building can transfer down to the foundation," Schafer said.

Schafer added that work on the second tower brings its own issue: creating openings in the existing floor to allow light into units while confirming the steel frame can handle the extra loads.

City officials have yet to identify the buckling cause. Both Schafer and Emily Guglielmo, a San Francisco structural engineer, suspect the added weight played a role.

Spokespeople for MetroLoft, the developer, did not reply to comment requests. Nathan Berman, the firm's founder, told The Wall Street Journal that extra weight from widening the top 15 floors or so probably led to the issue.

Guglielmo suggested the failure might stem from misunderstood original design assumptions, an error in design or construction, or crews overloading or compromising the structure.

Adding floors to existing buildings occurs often in dense cities with limited land, she noted, but it demands review of original documents and building inspection before assessing impacts from new stories.

"In places without extra space, more such adaptive reuse designs will appear," Guglielmo said.

Many structural engineers view demolition as an option only when necessary.

"Demolishing buildings wastes resources greatly," Schafer said, noting the construction sector accounts for about 40 percent of global energy-related carbon emissions. "Sustainability-wise, that poses a major problem."

Apart from environmental impacts, removing and transporting debris from large structures costs substantially in crowded cities like New York.

When safe reuse is possible, engineers favor it.

James LaFave, a structural engineering professor at the University of Illinois, said a steel-framed building from the 1960s like the former Pfizer site offers a strong base for conversion.

Officials nationwide have supported office-to-housing conversions to revive downtown areas hit since the pandemic.

New York has advanced this approach via zoning adjustments and tax breaks to boost housing. A city comptroller report last year identified 44 adaptive reuse projects completed, underway or feasible as of early 2025.

Pfizer vacated the building in 2023 after relocating near Penn Station, with construction starting in 2024.

Joshua Harris, director of Fordham University's Real Estate Institute, described office-to-residential conversions as vital for easing housing shortages in New York and elsewhere, despite inherent risks.

"In some ways it is not unexpected, and some understanding helps," he said. "These amount to intricate operations on aging structures."

"This reflects the effort to resolve the housing shortage," Harris added. "Such events can occur. While not as involved as a space launch, real estate work in Manhattan at 42nd Street and Second Avenue remains highly complex."

Guglielmo noted that building codes, inspections and skilled crews keep such failures uncommon.

"We benefit in the United States from avoiding daily incidents of this kind," she said. "Strong building codes guide safe engineering practices."

Harris observed that the event may prompt industry review, as conversions reshape business districts into mixed-use areas, similar to recent Wall Street changes.

"If this project faces an issue, other approved efforts will likely undergo checks for similar concerns," Harris said.

Rico reported from Atlanta and Hill reported from Las Vegas.