The first comprehensive zoning law in the United States: it divided New York into use districts and height districts, and required tall buildings to step back from the street as they rose, producing the setback skyscraper.
The Equitable Building of 1915, a sheer block of forty storeys that cast a shadow of several acres over lower Manhattan, precipitated the law. In each height district a building could rise at the street line to a height that was a multiple of the street’s width: once, one and a quarter, one and a half, twice or two and a half times. Above that it had to stay behind an inclined plane drawn from the centre of the street, which in practice meant setting back by a fixed ratio for every additional storey. On a quarter of the lot, a tower could rise without any limit at all.
The architect-draughtsman Hugh Ferriss drew the resulting “envelopes” as great stepped masses (1922) and in The Metropolis of Tomorrow (1929). Architects filled them with the tiered, ziggurat-like towers of the 1920s: the Barclay–Vesey Building, the Chanin, the Chrysler, the Empire State. The law was replaced in 1961 by a system of floor-area ratios and plazas.
The book, part by part
I Height districts and the tower rule
Street-wall height as a multiple of the street width; setbacks behind a sloping plane; unlimited height on 25% of the lot.
Rules: Setbacks behind a sloping plane · A tower on a quarter of the lot