Design flaw in foundation eyed as cause of Florida building collapse

Credit: TNS/ABACA via Reuters Connect - Search and rescue personnel search for survivors through the rubble at the Champlain Towers South Condo in Surfside, Florida

A design flaw at the bottom of a 135-unit condominium complex in south Florida might have caused the 40-year-old building to suddenly collapse on June 24, killing 18 people with as many as 145 still missing.

According to the latest media reports, faulty construction of the pool deck could have ultimately led to the destruction of a portion of Champlain Towers South, located in Surfside, FL, just north of Miami Beach.

The concrete of the pool deck was built flat instead of sloped, allowing water to collect and seep down to the parking garage below, where long-term corrosion is said to have compromised the integrity of the entire structure.

The deterioration of the building’s foundation was discovered during an inspection in 2018, and the Champlain Towers South Condominium Association had plans to mitigate the damage, however steep costs and indecision over how to pay for them prolonged the process of setting a plan in motion. 

It is customary for condo owners to be responsible for sharing the costs of repairs to the building itself. With a price tag quoted at $16 million for the necessary work, it’s not surprising there were lengthy discussions over how to cover the considerable expense.  

A team of specialists are now studying the wreckage, as well as inspection reports, to determine exactly what brought down the 13-story building without warning in the middle of the night. 

About half of the units in the complex crumbled to the ground at 1:30 a.m. one week ago. A surveillance video released by the New York Times suggests part of the structure first slumped, seemingly falling vertically in one giant piece, as if the columns had failed beneath the southern edge of the center of the building, not far from the pool. The failure quickly spread and brought down the entire center of the building. Seconds later, a large section to the east also fell. The destruction took less than a minute.  

Was the local environment a contributing factor in the collapse?

According to a recent academic study, the building, which was built in 1981 by late Miami beach developer Nathan Reiber, had been sinking 2 millimeters per year since the 1990s due to subsidence, or settling of the ground in what was once a marshland area.

The investigation into what reports are saying might be the deadliest accidental building collapse in American history has just begun, with a half-dozen scientists and engineers who specialize in disastrous structure failures on site to collect first-hand information on the cause of the failure, the AP reported.

The catastrophic collapse of an occupied building (not caused by a bomb or earthquake) is rare and investigators are struggling to understand how it could have happened with so little immediate warning.

Jason Averill, an official at the National Institute of Standards and Technology, said the team will collect information with the goal of preventing another such disaster. 

An explanation for the cause could directly impact buildings near Champlain Towers South but also the entire area of south Florida, where decades-old high-rise condos are everywhere. Their construction along the rising coastline of the Atlantic Ocean, amid increasingly frequent and severe hurricanes and storm surges, paints a risky picture for residents of the region. 

Damage had “gotten significantly worse” 

An assessment of the building in 2018 by engineering firm Morabito Consultants revealed evidence of “major structural damage” to the concrete slab below the pool deck and “abundant” cracking and crumbling of the columns, beams and walls of the parking garage under the building, according to documents released by the town of Surfside, Florida.

Failed waterproofing below the building’s pool deck was said to be causing structural damage in the concrete foundation of the building and that “failure to replace the waterproofing in the near future will cause the extent of the concrete deterioration to expand exponentially,” the report said.

A letter sent on April 9 from the president of the Champlain Towers South Condominium Association said damage to the building’s basement garage had “gotten significantly worse” since the inspection in 2018 and that deterioration of the building’s concrete was “accelerating,” according to reports, which noted the estimated bill for all repairs had increased from about $9.1 million in 2018 to $16.2 million this year. 

As recently as 36 hours before the collapse, a commercial pool contractor who visited the building noticed standing water in the basement-level garage.

“There was standing water all over the parking garage,” the contractor, who asked not to be named, told the Miami Herald. He noted cracking concrete and severely corroded rebar under the pool.

The contractor visited the condo building to put together a bid for a cosmetic restoration of the pool as well as to price out new pool equipment — a small piece of the multimillion-dollar restoration project that just was getting underway.

The contractor reportedly found the amount of water at Champlain Towers so unusual that he mentioned it to a building staff member.

“He thought it was waterproofing issues,” the contractor said of the staff member. “I thought to myself, that’s not normal.” He said the staff member told him they pumped the pool equipment room so frequently that the building had to replace pump motors every two years, but he never mentioned anything about structural damage or cracks in the concrete above.

Where was the oversight?

Condominium associations are self-governed and reports indicate the latest inspection in 2018 was not required by any local, state or federal bodies. Questions now center on whether there should be more oversight, particularly in Florida, a state known for its liberal regulatory style. 

To that end, state Sen. Annette Taddeo said on Twitter that changes to building inspection rules must be made: “Buildings need to be inspected much sooner than 40 years, especially in a county where sea-level rise can affect a foundation.”