Design flaws in the pool deck of the Surfside, Florida, apartment building where a partial collapse killed 98 people put the building at risk of failure before it was even built, federal investigators said Thursday.
Poor construction of the deck in 1981 further weakened Champlain Towers South, the investigators said. And over the next four decades, corrosion, along with renovations that placed a heavier load than the deck was designed to hold, made the building even more vulnerable, the investigators said.
“The conditions that existed in the pool deck slab at that time represented a serious safety concern for the building,” Glenn Bell, a lead investigator for the National Institute for Standards and Technology, said in a public meeting at the agency’s Maryland headquarters.
Whether those deficiencies directly caused the June 24, 2021 collapse is not yet clear (NIST’s final report on the cause isn’t expected until May 2025). Champlain Towers South, built on a barrier island, suffered from faulty construction and structural damage, including corrosion beyond the pool deck, according to an engineer that assessed the building three years before the collapse. Scientists have also documented saltwater seeping into the building’s underground foundation, and that the building had slowly sunk in the 1990s.
But the preliminary analysis outlined Thursday showed that investigators consider the pool deck’s many defects as a leading hypothesis — among about two dozen — of what led a large section of the 12-story residential building to suddenly crumple in the middle of the night.
The pool deck plan “fell well short of the applicable building code,” Bell told NIST’s National Construction Safety Team Advisory Committee. “So from the beginning, the original structural design provided low margins of safety.”
An “improper” placement of steel reinforcement in the pool deck slab weakened it, Bell said. Renovations loaded the pool deck with heavy materials, including planters, palm trees and sand, that the original design did not consider. Corrosion of the steel bars holding the concrete slab in place made the risk of failure higher, Bell said.
“All of these factors combined to result in margins of safety and margins against failure in some areas of the pool that were critically low at the time of the collapse,” Bell said.
Investigators said they are also considering that the collapse might be due in part to design and construction deficiencies in the residential tower that led to supports being overstressed. They are looking into the possible effects of climate change, including whether it played a role in the upward pressure of water on the building’s basement slab. And they are analyzing changes to the concrete and soil.
James Harris, another NIST investigator, said the “quality issues” that imperiled Champlain Towers South were “eerily parallel” to the factors that contributed to a collapse of elevated walkways at the Hyatt Regency Hotel in Kansas City in 1981, around the time Champlain Towers South was built.
Martin Langesfeld, whose sister and brother-in-law were killed, attended Thursday’s meeting by video and said NIST was taking too long to find answers. He cited plans to build a luxury high rise on the Champlain Towers South site, construction that could begin before NIST’s final report is issued.
“If the new development proceeds and the land is built upon while it’s deemed unsafe, and another building collapses, it will rest in the hands of NIST, the town of Surfside, the state of Florida and the federal government,” Langesfeld said.