FORT LAUDERDALE, Fla. — Around the globe, the rare and tragic collapse of a 40-year-old condo tower in Surfside has motivated residents to scrutinize their buildings with fresh eyes. We’re checking out every crack, chip and rust stain and asking whether they might portend a catastrophe.
It’s a challenging task. Unless you have an engineering degree, real-world experience and sophisticated testing equipment, it’s difficult to discern the difference between cracks caused by normal settling and others warning of shifts in the earth below that could result in serious damage if left unrepaired.
But the increase in attention — around the world — might be the only good thing to come out of such a grim event, according to construction restoration engineers.
The tragedy was a wakeup call for building owners, residents and government officials everywhere, said Syed Mehdi Ashraf, a South Florida engineering consultant and author who has taught courses in structural steel and prestressed concrete at Florida International University’s Department of Civil Engineering. Construction engineers overseas are fascinated that such a failure — whatever ends up being the cause — happened in the United States, which develops building codes other countries follow, he said.
“It’s on the front pages of newspapers in India and Great Britain,” he said. “I got a call from India,” his native country, “from a former classmate who said the government is rapidly trying to audit the buildings in the state. He asked me if I wanted to help and I said, ‘Yes.’”
Calls from commercial high-rise owners to Foundation Professionals of Florida, a geotechnical engineering consulting firm with offices in Hollywood and throughout the state, have increased 25% to 30% since the collapse, said company vice president David Brown.
Callers are seeking the company’s help interpreting warning signs and whether they warrant further testing or repair, Brown said.
The signs include:
Cracked or crumbling concrete
Decades ago, builders often mixed concrete at project sites, Ashraf said. As hard as it might be to imagine today, some builders used beach sand to mix concrete used for beachfront structures. The salt in the beach sand worked with the salt blowing off the ocean to speed up deterioration of the concrete and corrosion of the steel reinforcing bars that hold the concrete in place, he said. Even for beachfront buildings not composed of concrete made with beach sand, salt air is brutal, he said.
“It starts with hairline cracks in the concrete. They kind of widen. Then you start seeing bulging, and it becomes soft on the surface.” The bulges get larger until the concrete begins falling in chunks, a process called spalling. Dark brown stains are signs that the steel reinforcement bars are corroding.
Spalling can occur in several places along slabs or columns. As the concrete is eaten away, it becomes more porous, allowing more water to reach the steel, which then shrinks in diameter. Ultimately, the steel and concrete become so weak they can no longer support as much force as when the building was new, he said.
Today, concrete is mixed off site and is much more resistant to spalling, Ashraf said. “A building constructed in 2021 should not generate as much concern in 2061 as we have today about a building built in 1981,” he said.
Cracks in walls, window frames or floors can be signs of trouble, Foundation Professionals spokeswoman Nicole Gunter wrote in a blog entry posted on her company’s website.
Even a slight movement of the foundation can cause difficulty opening or closing windows or doors, she said. Stright-line cracks in floor tiles that run from wall to wall can be a sign of foundation damage. Chances are good that under the tile, the concrete foundation has developed cracks as well.
Uneven or bowing walls or floors
Sometimes areas of the floor will be sunken, heaved or sloped. Look for bowing floors or areas where floors are separating from walls.
Diagonal cracks at the corners of windows and doors
Cracks that start at the top corners of doors or windows and extend toward the ceiling can be a sign of a shifting foundation. Hairline cracks might not be anything to worry about. It happens when new homes settle a bit or if a house is left vacant without climate control for a period of time, Gunter said. But if the cracks are large, “that means a shift in the foundation,” she said.
When water saturates the soil under a building, it can cause the weight of the building to push one side of the foundation deeper into the soil. Meanwhile, the dry inside edge of the foundation pulls up. Wall rotation is a serious problem, Gunter said.
Other warning signs
—Stairstep cracks on the exterior or interior.
—Gaps between walls and the ceiling, between the ceiling and floor, or both.
—Popping sounds from roof trusses.
—Porches or chimneys that have separated from the house.
—Cracked or out-of-place moulding.
—Cabinets or doors that swing open.
—Water intrusion in the basement.
Shifts in foundations can be caused by a number of issues. A builder might not have compacted the fill dirt brought to the project site to the density needed to minimize settlement.
“If a builder is in a hurry, sometimes they’ll leave tree stumps in the ground and fill in the dirt around them,” she said. As the tree stumps and their root systems decompose, cavities are created and the fill dirt moves into them.
Jim Olsen, director of geology and geophysics for Geohazards Engineering and Geology, which frequently works with Foundation Professionals on restoration projects, says his company is also fielding more requests for testing services since the Surfside collapse.
It’s better to err on the side of caution, he said. “You should be aware of the conditions you are living in. Is there distress to the structure? Has it been kept up well?”
A decade ago in Sarasota, residents of the Dolphin Tower high-rise condominiums averted a Surfside-level catastrophe after the building’s property manager recognized signs of rapid deterioration and quickly summoned engineers to determine what was happening.
Entering their unit one day in 2010, the managers found the front door was stuck to its frame and difficult to open. Cupboards were prying loose from bowing drywall. Beneath their feet, tile was cracked and chipped in several places.
Engineers installed thousands of shoring posts to prevent the 37-year-old building’s upper 12 stories from collapsing above its three-story parking garage. Residents of the building’s 117 units were evacuated for what turned out to be $9 million of restoration work lasting five years.
A 24-inch elevated “transfer slab” separating the parking garage from the residential stories above it turned out to be the culprit, said Hythm Bakr, owner of The Bakr Group LLC, a Sarasota-based consulting firm that worked on the restoration project. Unequal forces to the underside of the slab led to cracks that would have eventually collapsed the slab in a phenomenon called “punching shear.”
That’s not likely what led to the collapse of the Champlain Towers South in Surfside, Bakr said. However, warning signs that something very dangerous was taking place near the base of the building were similar to those that should alarm residents of any building to look further, he said.
“People just need to be vigilant,” he said. “Watch and keep an eye out for signs.”
Owners who suspect threats to the structural integrity of their buildings should seek a professional opinion, Brown said. His company will come out at no charge and perform a visual inspection. “We’ll let them know if we feel it needs nothing,” he said.
And it may well need nothing. Some cracks result from normal settling while other seemingly serious issues, such as a balcony separating from its exterior fastening, might not signify larger structural problems, Gunter said. “Balconies can collapse on their own, and not always part of the main structure or the main structural integrity,” she said. “Sometimes the structure fails and with it goes the balcony.”
Gunter recommended having a separating balcony inspected by a geotechnical consultant.
To be sure, costs can mount if further testing and repairs are required for any structural damage, Brown said. Homeowners insurance will cover many issues, but not others, Olsen said, adding that sometimes consumers have to put up a fight to get their insurer to fund repairs.
Consumers should be wary of companies that feed off fear and are eager to begin work before conducting a thorough analysis, Olsen said.
Call three companies and ask a lot of questions, Brown advises. Ask the companies to show examples of previous work and what companies they’ve worked for, he said. Find out how long they’ve been in business. And, he warns, beware of startups heading to South Florida to exploit the newfound concerns.