Solving a Problem Underground

Down under. When leaking first appeared at the basement level on the north side of a landmarked Midtown condo, the board allocated $3 million from its reserve fund to make repairs. As it turned out, that hefty sum would pay for only a fraction of the much bigger problem that lay beneath the property — its vault spaces. Originally used for coal storage, these enclosed — and often forgotten — spaces are an extension of the basement that can extend beyond the property line and under the street. The condo, which dates to the early 1900s and has foundations on the site of at least five previously demolished buildings, had several different vaults of varying age and size, all in various states of disrepair.

It’s complicated. “These vaults are just voids,” says Richard Onde, a director of project management at the construction and property consultancy Gardiner & Theobald. Given their location under the sidewalk, the overhead load capacity of vaults needs to be 600 pounds per square foot, roughly the weight of a firetruck. As a result, vault repairs can get especially knotty since they involve a maze of city agencies. Compliance is needed with the Department of Buildings, the Department of Transportation and, in some cases, the Landmarks Preservation Commission. Utility companies may also be involved, as well as the MTA if the building is near a subway station. And as the condo board discovered, vault repairs often involve the added complication of revocable consent, a legal tool that allows the city to approve the continued use of inalienable property — which in this case was the building’s vault space extending under the street — and it comes at a price.

Revocable consent. Indeed, while seeking revocable consent for the continued use of its vault space beyond the curb, the board learned that the annual fee, which was nonnegotiable, started in the thousands of dollars and increased every year. “It gets very expensive over time — hundreds of thousands, and ultimately millions of dollars over 20 or 30 years,” says Onde, who is overseeing the condo’s vault remediation.

Drawing the line. To avoid these costs, as well as red tape, the board decided it would abandon the vault space stretching under the street, add a new foundation wall at the building’s property line and backfill the empty space. However, just as the repairs were finishing on the north side, a sidewalk collapse on a different frontage revealed even more serious vault problems on the building’s west side. These leaks had gone unnoticed because the space was occupied by a commercial tenant. “When we finally got in there, we could tell that things were far worse than we knew,” the board president says. Once again, the board decided to abandon the space under the road and build a new foundation wall at the western property line.

Money well spent. While the condo won’t have to pay costly consent fees, the final price tag is eye-watering. Having just spent $3 million on the north-side vault repairs, the board sought a $12 million assessment, with $8 million intended for the west-side repairs. The assessment doubles common charges for unit-owners over two years. “A lot of buildings are not prepared for the repairs and assessments that are needed,” Onde says.

Vault demolition on the building’s west side began in spring 2023. “The entire building will have all-new underground infrastructure supporting the sidewalks, new sidewalks surrounding the building, new foundation walls and new waterproofing on the inside and outside,” Onde says, adding that the project is expected to be completed this summer.