Federal investigators said Sept. 9 that the catastrophic collapse of Champlain Towers South in Surfside, Fla., likely began in the pool deck.
The National Institute of Standards and Technology reported that results from structural testing and high-fidelity computer simulations show a slab-column connection in the deck was the probable point of origin for the June 24, 2021, failure that killed 98 people.
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“The results of these efforts indicate that it is more likely that the failure started in a pool deck slab-column connection,” said Glenn Bell, co-lead investigator for NIST’s National Construction Safety Team. He added that simulation runs and laboratory tests of slab-to-column joints consistently aligned with video evidence, which captured the pool deck beginning to fall away before the tower itself collapsed.
NIST said the pool deck and the street-level parking deck began failing at least seven minutes before the residential tower came down. Investigators cited large-scale tests of concrete assemblies, digital modeling calibrated against security footage and review of building records.
The evidence pointed to local deterioration concentrated near the eastern section of the pool deck, where a sliding glass door dislodged from its frame, horizontal cracks spread along planter walls, and a steel gate dropped out of alignment and jammed.
Water infiltration into the garage ceiling was observed the day before the collapse, with flow rates sharply increasing in the final hours before failure.
Judith Mitrani-Reiser, investigative lead, said the team’s ongoing technical work is focused on reinforcing steel corrosion, concrete shrinkage and improperly constructed joints within the pool deck slab. “This tragic event has revealed flaws in our systems, and quality is at the heart of it,” she said.
Mitrani-Reiser also noted that certain reinforcement bars in the deck were placed shallower than design drawings specified, reducing their ability to transfer shear forces into columns. In addition, heavy landscaping planters added during construction introduced unaccounted-for loads, which further stressed slab-column connections.
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The investigation has also confirmed that waterproofing membranes under the pool deck had long since failed, allowing chlorides from saltwater intrusion to corrode reinforcement.
“The signs of distress we documented were concentrated in a relatively small area of the pool deck and street-level parking deck,” Mitrani-Reiser said, underscoring that the initiation point was both localized and predictable in hindsight.
NIST expects to complete its technical analysis by the end of 2025 and to issue a draft summary report and six detailed technical reports in spring 2026.
An aerial image of Champlain Towers South, annotated by the National Institute of Standards and Technology, shows the pool deck and adjoining areas where investigators say the collapse likely initiated. NIST’s Sept. 9 preliminary findings cite a slab-column connection in the pool deck as the probable origin point of failure. Miami-Dade County Open Data Hub/NIST In the Wake of a Tragedy
In the aftermath of the collapse, Florida lawmakers overhauled condominium law to strengthen inspection and reserve requirements.
Under statutory revisions to Chapter 718 of the Florida Statutes, associations for buildings three stories or higher must now complete a structural integrity reserve study every 10 years.
Beginning with budgets adopted after Dec. 31, 2024, those studies dictate mandatory funding levels for structural elements such as load-bearing walls, primary structural members, roofs, waterproofing, electrical and plumbing systems. Unit owners can no longer waive or underfund these reserves.
Existing associations must complete their first structural integrity reserve study by Dec. 31, 2025.
The statutes also require milestone inspections for taller buildings under Section 553.899, with reporting requirements tied to recertification cycles, and obligating developers to deliver turnover inspection reports when control shifts to residents.
Florida’s Legislature enacted the measures in 2022 and has since refined them to clarify thresholds and funding obligations, aiming to catch deterioration before it becomes catastrophic.
With the release of its preliminary findings, NIST said it will continue refining its analyses of structural failure modes and environmental effects, with final conclusions and safety recommendations expected next year.
