Is your NYC building at risk of collapse? Here are a few signs to look out for.

While it may have seemed unexpected to some, the collapse of a seven-story building in the Bronx Monday afternoon was likely preceded by early warning signs, according to private engineers who specialize in building collapses.

“I can give you a litany of things that people should look out for, but it's all related to if you see something changing in a relatively short period of time,” said Allyn Kilsheimer, a structural engineer who has studied collapsed buildings for 55 years, ranging from the Alfred P. Murrah Federal Building in Oklahoma City to the Champlain Towers in Florida.

Kilsheimer listed a number of signs to look for. If a marble rolls across the floor when it normally wouldn’t; walls that start to bulge; windows that used to open, but now they stick.

“The key is, if you see a change,” he said in a phone interview. “If you see cracks on the plaster on the inside that are new, or cracks that have gotten bigger.”

New noises, he added, often precede many collapses.

For residents who suspect potentially unsafe conditions, the city’s Department of Buildings strongly encourages them to call 311 right away.

“DOB considers 311 complaints about the structural stability of buildings as a top priority, and responds within 24 hours,” Andrew Rudansky, a Department of Buildings spokesperson, wrote in an email.

However, Kilsheimer and other physical engineers didn’t list calling the city as the first step in non-emergency situations.

“Getting the building department to respond is sometimes difficult,” Kilsheimer said.

“Keep in mind,” Joseph Pasaturo with AVT Engineering said, “If they see something that they consider unsafe, they may issue a vacate order, or at a minimum they're going to write a violation on the building.”

Pasaturo is one of many independent engineers in the city who do private inspections of buildings and issue a report to the building owner.

“If it's serious enough, we're going to tell them this needs immediate repair, you got to get out of the building, and I have to call the Buildings Department,” he said.

Pasaturo said an average evaluation and report for a five-story brownstone will cost about $1,500. Costs can quickly escalate if there are issues that need to be addressed.

For larger buildings, like a seven-story tenement, an engineering firm will charge about $2,500 for a licensed engineer to do a noninvasive inspection, he said.

Pasaturo also recommended that residents be generally aware of what's happening in their building. If there’s construction underway, residents can search the Department of Buildings Building Information System for recent inspections, reports, and violations.

“If you are over six stories in height, every building every five years has to have its exterior inspected by a licensed engineer,” Pasaturo said. “We would write a report on the condition of the exterior of the building and we have to file that with the city.”