Addressing Sinking Oceanfront Condo Towers 'Should Be High Priority,' Researchers Say

After releasing a bombshell study in December that revealed that dozens of skyscrapers are sinking on the wealthy barrier island communities of Miami-Dade County, the authors are calling for further investigation and action from the state and local governments.

At least 35 buildings in Miami Beach, Surfside, Sunny Isles Beach and Bal Harbour are sinking at faster than the expected rate, according to a Dec. 13 study by the University of Miami. The dozen authors who conducted the research say that while the buildings are safe today, more study is needed to determine the effect new construction has on surrounding buildings in one of the most valuable stretches of real estate in America. 

“We must continue to invest resources to develop technologies and predictive models for assessing risks, mapping risk zones and factors, and take measures through changes in codes and standards,” Khaled Sobhan, an author of the study and professor at Florida Atlantic University, told Bisnow in an email. “This should be a high priority at the State level for the safety of our residents.”

Luxury condo towers like Surf Club, Porsche Design Tower and Faena House are experiencing subsidence — when the ground beneath a building sinks, potentially leading to structural damage — of between 2 and 10 centimeters, according to the study. 

The researchers analyzed satellite radar technology to look at displacement in buildings from 2016 to 2023. They wrote that the rate of subsidence on the coast suggests that construction may be causing shifts in the rock into which their foundations are built.

“Structures do undergo long-term settlement depending on the soil strata,” Sobhan wrote. “Since the buildings mentioned in the study are supported by deep foundations embedded in the rock layers, the observed movements/rates are indeed concerning.”

Florida’s limestone contains interbedded sand layers that may shift due to ground vibrations caused by construction activity — a process referred to as “creep” in the report — which can either worsen or trigger subsidence in structures up to 1,000 feet away.

The study spurred worries about current construction practices, bringing renewed attention to the stability of these buildings. The authors said their work was spurred by the Champlain Towers South Collapse in Surfside that killed 98 people in 2021. The collapse “has highlighted the need for monitoring of building stability, especially in coastal areas with corrosive environmental conditions,” the report states.

Surfside Mayor Charles Burkett said the town continues to monitor and comply with all existing regulations, but there isn’t much else it can do.

“We are hopeful that Dade County will review the information and act on the same if necessary,” Burkett told Bisnow in an email. “While we are concerned with any information that points to problems with buildings and construction, little Surfside is not the place where the problem will be addressed, nor do we have the resources to accomplish the same.”

Surfside Vice Mayor Tina Paul told the Miami Herald last month that there is a “definite need to have more oversight and accountability for new construction projects.”

Flaws in construction and a lack of proper maintenance are considered the main cause of the collapse rather than subsidence, but a final federal report on the tragedy is expected to be released in 2026. The study found no displacements for Champlain Towers South, but that's because the satellite images were inconclusive, authors wrote.

While subsidence doesn't necessarily cause damage, if buildings sink unevenly, it could lead to cracks in their foundation and other structural issues.

Esber Andiroglu, one of Sobhan’s colleagues on the study and a professor of architectural engineering at the University of Miami, told the Miami Beach Historic Preservation Board last week that more research is needed to fully grasp where Miami’s coastal structures stand.

“These are all investigation areas that we really need to expand to, if we can receive the support, the necessary means and collaborations to conduct that,” Andiroglu told the board. “We're here and eager to start on it.” 

Researchers from the University of Miami’s Rosenstiel School of Marine, Atmospheric, and Earth Science and the University of Houston’s Department of Civil and Environmental Engineering led the study using a satellite radar technology named Interferometric Synthetic Aperture Radar, or InSAR. 

Due to limited resources, the research only focused on areas that were easier to detect and validate with the InSAR technology, such as Sunny Isles Beach, where 70% of coastal structures built in the last 10 years displayed signs of subsidence.

In response to the study’s findings, Sunny Isles Beach Mayor Larisa Svechin told the Herald in December that she is “100% confident that everything is safe.” 

Construction might not be the sole cause of the subsidence. Tidal-driven groundwater movements and stormwater injection into the subsurface of buildings, a common practice for flood management, also could be a factor in buildings sinking further. Any future research should take groundwater movements, including sea level rise, into account, Sobhan said.

“More research is needed to answer some questions explaining the observed behaviors of the buildings,” Sobhan said. “In the light of our findings, all relevant parties should be alert and revisit methods and practices.”

The study also found that older buildings experience sudden sinking in response to new construction, which is evident considering the barrier islands are a hotspot for development and the luxury towers mentioned in the study are worth billions of dollars combined.

At The Surf Club on Collins Avenue in Surfside, for example, Fort Lauderdale-based Fort Partners built the Four Seasons Hotel and Residences in 2017 and sold the 151 units for more than $1B combined, including to Miami Heat President Pat Riley. The developer is now building two other luxury projects on the same block, The Real Deal reported.

The Bentley Residences in Sunny Isles Beach development site experienced 4 centimeters of displacement, according to the study. Still under construction, the site's expected completion is 2027. The 62-story tower has almost half of the units sold, with pricing starting at $5.8M and a penthouse that is selling for $37M, duPont Registry reported in September.

One of the only two projects in Miami Beach that were found to experience subsidence, Faena House in Miami Beach, opened in 2016 and was one of four hotels in South Florida to receive two keys from Michelin Guide’s new hotel rating system. The 18-story, ultra-luxury L’Atelier Condominium had 2 centimeters of observed displacement between 2019 and 2023, according to the study. 

Despite having fewer identified sinking structures than its smaller neighbors to the north, Miami Beach's Historic Preservation Board reached out to the study's authors to learn more about their findings and what next steps it could take — and to tamp down any panic.

“I think that we all want to collaborate to make sure that we get as much information as we can on what is actually going on here,” Haskel Mayer, a board member of the Historic Preservation Board, said. “I don't think that anybody here wants to be hyperbolic in any of our assessments.”

The lessons learned from past tragedies remain top of mind for those involved in the research and the cities it impacts– where surprises aren’t always welcome.

“We must not forget that the Surfside tragedy caught everybody by surprise along with a sense of fear and uncertainty,” Sobhan said. “It is a failure at every level if we are unable to inform the communities of the risks.”