I talked a bit about this type of detail recently but I was surprised to learn that I hadn’t posted these pictures. This is a middle-third of the 1800s tenement in Hell’s Kitchen that was built with retail space on the first floor. The wood joists of the floors and roof span left to right, supported by the side walls and two interior walls in line with the two columns on the facade we’re looking at.
Both street facades are supported on these cast-iron arches tied with wrought-iron rods, and the arches are supported on cast-iron columns. The fascias at the tops of the old storefronts, which probably carried signs for the stores, hid everything from the rods up to the top of the brick band above the arches. I happened to be in the right place, at the right time, with a camera in my hand to get a series of pictures that show the structure exposed.
It’s not an accident that the arches are so shallow. First, it’s easier to transition from iron to brick if the arch curve is shallow. Second, it was easier to cast the nearly-straight arch pieces than it would have been to cast more curved pieces. Most importantly, the shallower an arch is, the greater its horizontal thrust, but the use of the wrought-iron ties meant that thrust was not a problem here.
As I said before, this is a clever detail that uses the commonly-available technology of the era to do something quite difficult: support a masonry wall over a large void.
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