Marianne Schaefer in Bricks & Bucks on May 16, 2018
A 240-unit co-op in the Bronx got some good news and some bad news. The bad news was that a large chunk of concrete broke loose from the ceiling of the lower level of the co-op’s two-level parking garage, crashing to the floor. The good news was that the area was vacant at the time. No cars got crushed, and nobody got hurt.
“The reinforced concrete was from the original 1950s construction,” says Vincent Nicoletti, project engineer with PVE Engineering. “They called us right away. We had them move all the cars above and below that area and we did a quick assessment of the condition of the concrete.” PVE Engineering did a sounding, which means workers went in with hammers searching for hollowed-out spaces, which indicate that the metal rebars have corroded and the structural integrity of the concrete has been compromised.
“We determined that the concrete fell down because the rebars had rusted,” says Nicoletti. “Rust expands and puts pressure on the surrounding area. That will dislodge the concrete and make everything unstable. Pretty much all the steel in that area was badly corroded.”
This process is significantly accelerated by chloride, a chemical found in rock salt, which is used on roadways to prevent the build-up of snow and ice. Cars then carry it into covered garages, where there is no rain to wash away the salt deposits.
“For most people, a parking garage is just a place where they park their cars,” says Nicoletti. “They don’t really give it the same kind of cleaning and maintenance they would give their lobby or their hallways.” Nicoletti recommends preventive maintenance – bi-annual power washing to purge rock salt. Of course all the cars have to be moved out of the way, a major headache for the car owners and one of the reasons why many boards neglect preventive maintenance.
“A garage is a cash cow – and that’s why their maintenance gets neglected,” says Eric Cowley, principal at Cowley Engineering, who has repaired hundreds of garages. The cost of power washing is not prohibitive – typically 10 to 25 cents per square foot, a fraction of the cost of replacing compromised concrete. Cowley and Nicoletti also recommend installing membranes, frequently made of epoxy and polyurethane, on heavily travelled stretches of concrete. These membranes, which seal the surface and keep water out of the slabs, cost between $10 and $20 per square foot and have a life span anywhere from 10 to 20 years, depending on the quality of the product.
“These [membranes] prevent corrosion of the metal parts,” says Nicoletti. “They also have to be maintained. If they are not maintained or if they go beyond their typical life spans, one will see tears or it bubbles up or pieces start to break away, and then water can get into the slab.”
Engineering firms also recommend a survey of the garage every four to five years, a kind of x-ray to identify problems ahead of time. “It’s like with every diagnosis,” says Nicoletti. “The earlier you know, the less it will cost to repair. The longer you wait, the more limited the options.”
If major repairs are in order, Cowley advises scheduling them for August, when many residents drive out of the city, thus minimizing inconvenience. But in major concrete replacements, noise, dust, and vibration are always facts of life.
The cost for the repairs in the Bronx co-op garage totaled $60,000. Crews had to cut out large sections of the sub-level roof and put in new reinforced concrete over the opening. “That’s usually the worst-case scenario,” says Nicoletti, adding that it’s another reason to perform rigorous preventive maintenance and periodic inspections.
In the long run, it pays to keep your cash cow healthy.
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