IN the days that followed Hurricane Sandy, the developer of the luxury condominium 150 Charles Street hunkered down with his team of architects and engineers to rethink the building’s design.
Just steps from the Hudson River, the construction site was partially flooded. “Their mandate was to figure out how the building would have stayed open in a storm like this,” said Steven Witkoff, the developer. “They came back with a list of five things, and we implemented every single one.”
The efforts delayed the project by some six weeks and added as much as $3 million to its cost.
It was one of a number of projects that convened their engineers and construction teams to reconsider their plans after the rising waters rushed over the city’s embankments and into the basements of countless residential buildings across Lower Manhattan.
Now, more than two months after the storm caused millions of dollars in damage, novel and costly waterproofing techniques are being employed, including the addition of backup generators and floodgates, and the relocation of mechanical equipment. The owners of buildings that predate the flooding are also looking at these measures, although retroactive installation is so complex and costly that some may decide not to do anything.
“If you are in the flood zone and you are marketing a new high-end property, it will need to stand up to the test of another superstorm,” said Stephen G. Kliegerman, the executive director of development marketing for Halstead Property. “I think buyers would happily pay to be relatively reassured they wouldn’t be terribly inconvenienced in case of a natural disaster.”
At 150 Charles Street, Mr. Witkoff plans to forestall a blackout by installing two natural-gas-powered generators on the roof to run the fire-alarm system, the emergency egress lighting, the elevators, and electrical and mechanical support equipment. Each apartment will be equipped with at least one electrical outlet connected to the generators. The developer is also ordering five-foot-tall floodgates that can be assembled and installed to encircle the building in a matter of hours. The gates, which fit together like toy Lincoln Logs, are to be stored in the basement.
Finally, Mr. Witkoff is using poured concrete instead of cinder block for the basement walls. And each basement mechanical room will be sealed with watertight submarine-style doors.
“This is the new normal,” said Adam Gordon, the president of Adam Gordon Holdings, which is building a condominium at 560 West 24th Street in Chelsea. “With two hurricanes in two years, this is the new base level for the way people should think about building in New York.”
Mr. Gordon’s Chelsea project will have a waterproof “concrete superstructure” from the basement to the second floor that has 13-foot floodgates; waterproofed rooms with submarine-style doors to protect mechanical and electrical systems; and a generator and a pumping system run on natural gas.
The floodgates are expected to cost Mr. Gordon roughly $100,000 — “not an insignificant cost, but not breathtaking.” He is still pricing the other waterproofing measures. The building, eight units averaging 3,300 square feet each with a ground-floor art gallery, is to be completed in spring 2014.
The developer Time Equities is rethinking the plans for its approximately 62-story condominium at 50 West Street. It is considering replacing a hotel with multilevel retail and, to make the building flood-resistant, moving the mechanical room onto the second or third floor. The developer is also looking at raising the sill height on the ground floor and using floodgates at the entrances.
After the storm, Time Equities hired the Albanese Organization, which built the Visionaire, the Verdesian and the Solaire in Battery Park City, to be its development manager.
“The Albanese Organization are the exact people to handle the project,” said Robert Singer, the director of development and acquisitions for Time Equities, “because Battery Park City was the only place that had electricity during the storm, while the rest of Lower Manhattan went dark.”