On June 22, the National Institute of Standards and Technology released technical findings and more details about the events leading up to the collapse of Champlain Towers South and the tragic deaths of 98 people that occurred five years ago.
The agency concluded that the collapse sequence began weeks before the building’s collapse, when two slab-to-column connections under the pool deck of the Surfside, Florida condominium experienced punching and shear failure, initiating a progressive sequence that culminated in the partial collapse of all 12 reinforced concrete stories on June 2, 2021.
“When building structures are designed and built to required codes and standards, they have margins against failure, which means they should be able to withstand much more load than they are expected to withstand,” said Judith Mitrani-Reiser, research co-director of NIST’s National Construction Safety Team, in a video presentation accompanying the findings.
“In the case of Champlain Towers South, however, these margins against failure were too narrow from the start,” he added.
The collapse sequence began weeks earlier
According to the agency, the collapse likely began in early June 2021, about three weeks before the tower fell, when two connections between the garage columns and the pool deck slab failed.
These initial mistakes did not immediately lead to the collapse. Instead, the surrounding portions of the pool deck and street-level parking structure temporarily absorbed the loads, increasing the demand on already vulnerable neighboring connections.
“Once the first connections failed, other elements of the pool deck were left to carry their loads,” the researchers said in the presentation. “But they weren’t strong enough to handle them because of problems that arose from the building’s original design and construction.”
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NIST said the failure spread through the pool deck and parking structure before progressing to the tower itself.
“The low margins against failure were primarily caused by two factors,” said Glenn Bell, co-director of the research. “First, the gross and widespread deviations in the building’s original structural design from the codes and standards of the time, but also some limitations in those codes and standards. And second, the deviations in the building’s construction from the design drawings.”
NIST said portions of the pool deck and street-level parking lot slab did not meet code requirements for flexural strength and strength at the slab-to-column connection, with some areas providing less than half the required strength.
The investigators also found construction deviations, such as poorly placed reinforcing steel and fewer rebars crossing columns than required by design.
Bell’s reference to “limitations in these codes and standards” suggests the findings may have implications beyond Champlain Towers South. While NIST did not identify specific code changes in its June 22 findings, the investigation focused heavily on slab column punching and shear behavior, joint performance, and the interaction between aging structures, added loads, and long-term deterioration. The agency said recommendations for changes to industry codes, standards and practices will be included in its final report.
Additional loads added during the life of the building further reduced the structural capacity, according to the agency. These include large planter boxes that were not shown in the original drawings, as well as subsequent rehabilitation work that added pavers and sand beds to parts of the pool deck system.
Long-term deterioration provided the final link in the failure sequence.
“We found no evidence of any specific initial event,” Bell said in the presentation. “The final factor that brought the critically low safety margins to the point of failure was most likely long-term corrosion degradation.”
NIST said the findings rule out several theories that emerged after the collapse, including vibrations from nearby construction, foundation failure, sinkholes, settlement, hurricane effects, explosions and accidental overloading from a roof project underway at the time.
The findings build on NIST’s September 2025 conclusion that the collapse originated in the pool deck.
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The results bolster Florida’s reforms
For Greg Batista, president of Fort Lauderdale-based G. Batista Engineering & Construction, the findings largely confirm patterns he’s found during decades of work assessing and repairing Florida’s aging condominiums.
“Nothing surprised me. Absolutely nothing,” Batista said. “After you’ve done this for so long, you can see a pattern, and the pattern just repeats and repeats and repeats.”
Batista, who said NIST interviewed him during the investigation, noted that the findings reinforce concerns engineers have long raised about deferred maintenance, deteriorating structures and the need for adequate funding to address problems before they become critical.
In his view, the findings also support the rationale for Florida’s post-Surfside condo reforms, including the structural integrity reserve studies and expanded inspection requirements enacted after the collapse.
“The biggest thing that sparked this bill was the structural integrity reserve study,” he said, referring to the state’s condominium safety legislation. “This requires boards and homeowners associations to have reservations.”
The requirement was designed to reduce the risk of associations postponing major structural repairs due to inadequate reserve funding, an issue that has come under heightened scrutiny since the collapse.
NIST said it will now prepare its final report, which will include supporting evidence, test results, computational modeling and recommendations for changes to building codes, standards and industry practices.
The agency did not provide a release date for this report.
