Flaws in the pool deck are thought to be the preliminary cause of the devastating collapse of a condominium in Surfside, Florida, that killed 98. Recent test results by the National Institute of Standards and Technology (NIST), the agency leading the investigation of the 2021 tragedy, reinforces the theory that the failure started in the pool deck area rather than in the tower itself. NIST released new findings this week. The investigation also identified indications of the building’s distress that were visible in the weeks before the partial collapse of the building.
Investigative lead Judith Mitrani-Reiser and co-lead Glenn Bell presented an update on the NIST investigation on Tuesday, September 9, at a virtual meeting of the National Construction Safety Team (NCST) Advisory Committee. Their presentation summarized the investigation’s activities and preliminary findings provided in previous updates, including an extensive video released in June 2025, and highlighted significant progress in the failure analysis since the June update.
Bell described the team’s current efforts to advance its evaluations of potential failure initiation scenarios through computer simulations, supported by the results of large-scale structural testing and evidence of the building’s distress in the weeks before failure. The team has also been refining its analysis of the impacts of steel reinforcement corrosion, concrete shrinkage, and improperly built construction joints in the pool deck slab.
According to Bell, the results of these efforts “indicate that it is more likely that the failure started in a pool deck slab-column connection.”
Bell also explained how the results of large-scale structural testing and computer analyses of video footage captured at the time of the collapse shed light on how the collapse progressed from the pool deck into and through the tower.
Mitrani-Reiser highlighted indications that the building was in distress in the weeks before the collapse. These included a sliding glass door that came off its frame, the previously reported horizontal crack in a planter wall and distress where the wall meets a planter box, and the vertical shifting of a gate, causing it to jam so that it could not be opened. All of these issues were concentrated in a small area of the pool deck and street-level parking deck, which has been confirmed to have begun collapsing at least seven minutes before the tower.
Additionally, the day before the collapse, water was seen leaking from the ceiling of the garage in an area that had been the site of many cracks and repairs over the years. The flow of water dramatically increased in the hours before the collapse.
Surfside is located a few miles north of Miami. NIST said its final conclusions on the collapse will be released before summer 2026.
Image – The NIST National Construction Safety Team developed this graphic showing where cracks had been identified in the first-floor slab in the months and years before the 2021 partial collapse of Champlain Towers South. The cracks are noted in turquoise, while construction joints (where concrete slabs meet) that are of interest to the investigation are shown in pink. Note the concentration of cracks in the street-level parking and pool decks. Courtesy of Miami-Dade County Open Data Hub/NIST.
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