Oh, That Sinking Feeling: The Subsidence of Multifamily
Multifamily communities in major cities along the Atlantic Coast are subject to sinking. Columnist Lew Sichelman explores what the impacts might be.

If residents of multifamily buildings along South Florida’s Atlantic beaches have been having a sinking feeling as of late, it might be for good reason. A recent study by the University of Miami has found that dozens of beachfront condominiums and hotels are actually sinking, some by as much as three inches.
A few inches may not sounds like much—but it could cause the structural integrity of the buildings to falter. And if there is uneven sinking, known as differential subsidence, one or more of the buildings could possibly collapse.
Researchers in the study, conducted by the Rosenstiel School of Marine, Atmospheric and Earth Science, looked at satellite images that can measure fractions of an inch to determine whether or not subsidence led, at least in part, to the 2021 collapse of Champlain in Surfside, Fla. The event killed 98 people and led to the requirement of structural review for older condos across the state.
While the researchers didn’t find any signs showing that subsidence was a cause of that cave in, they did come across evidence of the phenomenon in 35 buildings along Bal Harbour, Surfside and Miami Beach. And preliminary data indicates that some buildings along the coasts of the Broward and Palm Beach County coasts are also sinking.
The deeper issue
But the problem could be much broader. Experts in the study noted that almost all of the buildings on the coast are subsiding.
“The discovery of the extent of subsidence hotspots along the South Florida coastline was unexpected,” Farzaneh Aziz Zanjani, the report’s lead author, said in a prepared statement. “The study underscores the need for ongoing monitoring and a deeper understanding of the long-term implications for these structures.”
South Florida isn’t alone, either. Early last year, a study showed buildings in major cities along the entire Atlantic Coast were also sinking. The research from Virginia Tech and the U.S. Geological Survey found that areas of New York City, Long Island, N.Y., Baltimore and Virginia Beach, Va., were sinking more than the rate of the rise in seawater.
The buildings identified in the Florida report include the Surf Club Towers and Faena Hotel, the Porsche Design Tower, The Ritz-Carlton Residences, Trump Tower III and Trump International Beach Resorts. Together, the high rises contain tens of thousands of residents and visitors, as well as apartments sometimes costing more than $1 million.
Meanwhile, a deadline for Florida condominium inspections has come and gone. One of a flurry of new regulations put into effect after the Champlain collapse called for most owner-occupied apartment structures to obtain a visual inspection. And a state law required condo associations existing prior to July 1, 2022 to complete “a study of the reserve funds required for future major repairs and replacement of the common elements based on a visual inspections,” again by December 31.
Continued research
There is no record yet of how many condo properties complied with the requirements. But its unlikely that the problem will go away. Environment experts anticipate that with rising sea levels and building greenhouse gas emissions, the erosion of the limestone on which South Florida is built will continue to progress.
“It’s probably a much larger problem than we know,” Paul Chinowsky, a professor of civil engineering at the University of Colorado Boulder, told the Miami Herald.
It is common for buildings to subside a handful of inches during and shortly after construction: a natural effect as the weight of the building compresses the soil underneath. This won’t necessarily cause structural issues. But differential subsidence will. Consequently, the problem requires not only visual inspections, but further research to understand the long-term, structural implications.