The National Institute of Standards and Technology (NIST) released a report Monday concluding that the partial collapse of the Champlain Towers South condominium in Surfside, Florida, on June 24, 2021, began with a structural failure that occurred three weeks prior.
The report, issued nearly five years to the day after the disaster that killed 98 people, determined that the initial failure struck two critical garage column connections beneath the pool deck in early June 2021. That failure trapped the 12-story building in an undetected slow-motion domino effect that investigators say engineers had long suspected.
“When building structures are designed and built to required codes and standards, they have margins against failure, meaning they should be able to support much more load than they are expected to bear,” said NIST investigator Judith Mitrani-Reiser. “In the case of Champlain Towers South, however, these margins against failure were too narrow from the start.”
Over the subsequent 21 days, the pool deck’s concrete slab silently warped and fractured as the failing connections progressively shifted immense weight to adjacent columns. On June 24, the pool deck gave way entirely, pulling down a major portion of the building.
The federal investigation traced the complex’s vulnerabilities to its original design, which failed to meet the codes and standards in place when the building was built 40 years ago. Construction itself further deviated from the structure’s original design, compounding the weakness.
The addition of heavy landscape planters and thick paving stone on the pool deck in the 1990s stressed the building further, adding tons of uncalculated deadweight to the already deficient slab. Those additions, coupled with long-term corrosion, ultimately caused the collapse, according to the report.
In the weeks leading up to the disaster, the building showed physical warning signs that went undiagnosed. Those included a residential sliding glass door popping out of its frame, shifting entry gates that jammed shut, and a noticeable increase in water leaking through the garage ceiling in the hours before the final failure.