Afraid your apartment building may collapse? Here are signs experts say to watch out for.

NEW YORK ‒ On Monday, a seven-story tenement building in New York City partially collapsed, heaping a 12-foot mound of debris on the street and forcing over 170 people, including dozens of children, from their homes.

The dangerous incident followed complaints to authorities and a subsequent inspection. Experts say people living in older buildings across the country can learn from the circumstances surrounding the unexpected collapse.

While the only way to be certain of a building's structural integrity is to have it professionally evaluated, there are some red flags people can watch out for, experts told USA TODAY.

Is your building crumbling?

Abi Aghayere, a civil engineering professor at Drexel University who has studied structural failures for decades, said "tell-tale signs" of degradation include water intrusion; sagging ceilings; and cracks that seem to be expanding in walls. Residents should report all of these issues to the building owner, their landlords or the city they live in, Aghayere said.

Norbert J. Delatte, a professor of engineering at Oklahoma State University, said structural warnings most often appear in the form of changes: windows that no longer open, doors that are sticking, strange sounds, growing or moving cracks.

A good way to tell if a crack is expanding is to fill it in with spackle, Delatte said. If it opens up again, that could be a sign of trouble. Delatte also suggested people who are worried about their building should get a long level and see if their floors are drooping over time.

Both Aghayere and Delatte agreed while it's good to be vigilant, they cautioned against overzealous do-it-yourself inspections.

"If you start being hypersensitive to how your house is sounding and you start looking for cracks, you might get false positive indicators," Delatte said.

Bronx building's facade was deemed unsafe; complaints piled up

For years, people living at 1915 Billingsley Terrace complained that the building seemed to be crumbling around them.

In 2015, one resident warned in a complaint filed with the City of New York Department of Buildings that "THE BUILDING IS HIGHLY UNSTABLE. YOU CAN HEAR IT CRACKING AND DETERIORATING FROM THE INSIDE." Another complaint said the building was "OVERCROWDED" and that there were "CRACKS IN THE EXTERIOR WALLS," records show. These complaints were resolved by the city's buildings department.

In 2020, significant cracks around the building and other issues were meticulously recorded in an evaluation of the tenement's facade – the exterior walls that, in this case, were bearing the weight of the 96-year-old structure. New York City code requires owners of buildings higher than six stories to have the exterior walls inspected every five years.

Richard Koenigsberg, the engineer hired to inspect the Morris Heights building in 2020, determined the facade was "unsafe" but noted that it was not "imminently hazardous." The report never triggered a deeper inspection of the building's structural integrity, which would have had to be initiated by the owner, records show.

At a news conference on Monday night, James Oddo, the commissioner of the New York City Department of Buildings, mentioned Koenigsberg's report with the caveat that "Unsafe facade conditions is not the same as an unsafe building."

Repairs on the facade above the first floor were completed recently, Koenigsberg told USA TODAY. He said contractors were working on repairs leading up to Monday but that they were not working on the area where the building crumbled.

Koenigsberg said he believes the structural column at ground level of the building's northeast corner is to blame for the collapse – not the facade.

At the time when he submitted reports detailing the building's cracked bricks, damaged mortar and bowed parapet, Koenigsberg did not see its collapse "as foreseeable," he said.

The city's buildings department is investigating the cause of the incident, and the Bronx district attorney's office is looking into whether there was any potential criminal action. The building is owned by the shell company 1915 Realty LLC, which did not respond to requests for comment.

Aging housing, calls for more oversight

As America's housing stock ages, experts have advocated for greater oversight to prevent collapses. In New York City, which has had two prominent building collapses this year, the median residential building is almost 90 years old.

New York City Mayor Eric Adams acknowledge the age of tenements throughout the city at a news conference on Tuesday. “Many of our buildings come from an older stock," he said. "You have this from time to time.”

At the same conference, Deputy Mayor for Operations Meera Joshi said the city's buildings department does not employ enough staff to inspect all buildings citywide, and that they're looking to "sharpen tools," such as escalating fines to ensure landlords keep up with inspections and repairs.

"We're a city of millions of buildings and 500 and something inspectors," she said. "We will never – with boots on the ground – get to every building."

Aghayere said he hopes fines and other proposed sanctions prove effective in ensuring owners maintain their buildings because "this issue is not going away."

"I could find myself living in a building like that, and I can understand the apprehension that folks may be having," he said. "They need more protection."

Christopher Cann is a breaking news reporter for USA TODAY. Reach him via email at ccann@usatoday.com or follow him on X @ChrisCannFL.