For people unfamiliar with sidewalk vaults, the illustration above, from 1865, might seem plausible, but it’s actually Daniel Badger’s fantasy of how he could sell more iron. The left-hand side is reasonably accurate for mid-1800s vaults: the facade columns extend down past the plane of the sidewalk, marking the separation of the cellar proper from the vault space; the cast-iron vault lights (plates with glass lenses set into them) form the portion of sidewalk adjacent to the building; and the two halves of the sidewalk are supported on an asymmetrical-U cast-iron beam. The fantasy starts to the right of that beam, where Badger is showing more cast iron for the outer portion of the sidewalk, which was usually stone slabs; and where he shows the vault intentionally extended under the driving lanes of the street (vaults typically ended at the curb line until streets were widened for car traffic in the 1900s). He even shows a cast-iron gutter. In any case, the basic idea of extending the cellar under the sidewalk is clearly shown. Vaults built later used steel beams and concrete slabs (including concrete vault lights) instead of cast iron, but had the same basic layout.
This introduction has been a long-winded way of getting to the horrible news, which was the collapse of a vault roof (the sidewalk) seriously injuring a woman. I don’t know the details of what happened there, but I’ve seen enough vaults to discuss the topic a bit.
Vault space was a great thing in the nineteenth century. It could be and was used for coal storage, getting the potential fires and explosions of coal dust out of the body of the building. It could be and was used for boilers for the same reason. It could be used for storage for heavy objects, which makes sense when you remember that all those pretty cast-iron front loft buildings were warehouses and factories.
It gradually became more trouble than it was worth. The sidewalks leaked, and the cast-iron portions (particularly the vault lights) cracked under heavy loads. It was lousy space for anyone more sentient than a lump of coal. It was also, until 1997, taxed if it was usable. As a result, a lot of landlords closed off the interior access to the vaults, making them unusable and therefore untaxable, but also eliminating any possibility of maintenance. The tops of vaults were often covered with new sidewalk concrete, to the point where it is sometimes not possible to tell if a vault is present or not.
The New York City Department of Buildings has had some real success in digitizing records, but the focus has not surprisingly been on records pertinent to current regulations. The tax on vaults was handled by the Department of Finance, and those records have not been directly linked to the DoB records. Add this to the physical conditions and here’s the result: there are no accurate public records about which buildings have sidewalk vaults. In some cases there may not be accurate private records: if someone bought a building in 2000 that has a vault that was walled off in 1980, they may not even know that extension is there.
It’s hard to beat this record for obsolescence: vaults are so meaningless today that we don’t even know what’s out there. But we know that they are exposed to faster and more complete weathering than most building elements because of their location under sidewalks, and we know that they are typically not well maintained. I’m afraid there will be more incidents like the one on 158th Street.