Champlain Tower: Experts weigh in on what went wrong

Experts said it's unlikely a single issue caused the deadly collapse of the Champlain Tower South condominium complex, but a confluence of factors may have.

The oceanfront Surfside, Florida, complex, which was built in the 1980s and up for its 40-year recertification, collapsed Thursday. At least four people are dead, and 159 are still missing, officials said Saturday.

The Town of Surfside late Friday night released a trove of documents on the now-collapsed building, including inspection reports from 2018 that described several structural deficiencies of varying degrees, such as "failed waterproofing" near the pool deck and "abundant cracking and spalling" of concrete columns in the parking garage.

Jason Borden, a structural engineer whose firm had conducted an hour-long site survey of the building in 2020, said what he observed "was typical of a 40-year old building that had had some deferred maintenance." That means that parts of the building had reached their "expected useful life" and needed to be repaired or replaced, but added that his team did not see anything out of the ordinary, and certainly nothing potentially catastrophic.

Of the report, Borden told ABC News that the deficiencies "could have contributed" to the collapse "but they would have been one of multiple."

"Any of those items by themselves are unlikely to have been the sole reason why the collapse happened, but those combined with other things also could have been an issue added up to the overall net result," Borden added.

Miami-based architect Kobi Karp agreed, saying the collapse likely resulted from "a collection of bad things."

"There are certain deficiencies to the existing structure which were not maintained," Karp added.

Built in 1981, the Champlain Condominiums South Tower has endured hurricanes and the challenging South Florida climate for nearly 40 years. A Miami-area building collapse in 1974 prompted county lawmakers to enact a mandatory inspection review for commercial and residential buildings 40 years after they're constructed.

Construction on Champlain Tower South was just starting to get underway following the results of that 2018 report, and work was being done to replace the roof when the collapse happened, Ken Direktor, a lawyer for the condominium's board, told ABC earlier this week.

Borden added that an original building plan from 1979 that was also released overnight struck him as "robust," suggesting that deterioration and spalling columns in the lower levels over time "could have contributed to the progressive collapse of the building."

Dr. Atorod Azizinamini, a professor of civil engineering at the Florida International University, said that from a structural engineering perspective buildings should be inspected "more often than once every 40 years."

"I'm certain that there's going to be some lessons that's going to come out of this tragic event," Azizinamini said. "Hopefully that should provide us with some kind of roadmap to make any necessary changes to the way we do business, so that nothing like that happens."

Meanwhile, Surfside Vice Mayor Tina Paul, who was on the commission in 2018, told ABC News that she was not aware of this report when it was penned three years ago because it was a building department matter that was not brought to the attention of the commission at that time. But she pledged to find answers.

"Unfortunately, it appears nothing was done," Paul said. "The town is deeply concerned for the safety of all our condo residents and their homes, and we have brought in a structural engineer team to analyze what happened and look at our other buildings."