Interest in zoning keeps increasing, and NYC is one of the US cities where zoning matters enormously. It’s also commonly describe as “complicated”, and that can make us all lose track of the big picture.
So here’s an overview, meant for non-experts in zoning and urban planning, but interested in finding out what zoning is about, and what’s special in NYC, with a focus on residential buildings and informed by my background as an economist and data scientist.
Let’s introduce the history briefly, heavily influenced by the excellent book “Zoning Matters” (references below): In the past (generally before 1920s in NYC), construction was, by current standards, not much regulated. If you own a plot of land, you can do stuff with it. You might build a home for your family, or a big residential building, or you might put a factory there. This is full of what economists call “negative externalities”, because your neighbors might hate many of these uses.
Zoning arose from a mixture of bottom-up political pressure and higher-level (city, county, state, federal) regulation, with the goal of limiting these negative externalities. The federal government and states generally defer to local preferences, so zoning is truly quite local — to confirm that, just join a community board meeting in your neighborhood!
In general, zoning works by taking the city, dividing it into districts (a bit bigger than a block, and smaller than a neighborhood), and gives you constraints on what you can do and build there. The big categories are Residential (R), Commercial (C), and Manufacturing (M). And then (we’ll get back to this) each district also has an intensity. For a stylized example, in NYC, the R-1 district allows only single-family homes with plenty of space and R-6 allows up to a 4-story building.
Importantly, and different from, say, San Francisco, in NYC is “build of right”, which means that, if you’re proposing something that’s within the zoning code, others can’t really stop you from building it (see the appendix for the exemption process, called ULURP).
So let’s build some housing, and let’s look at it like a residential developer. Here’s what I’d do:
In theory, maximizing building area is a piece of cake: Each zoning area give the magical “Floor-Area-Ratio” = FAR, which tells you how much you can build as a share of the lot size. So let’s take a typical NYC townhouse lot (2500sq feet = 25x100feet), then if your zoning district says FAR=1, you can build up to 2,500sq on it. With FAR=2, you’d build up to 5,000, see this article for some nice illustrations. FAR is by far the most important variable, because it’s this huge lever that tells you how much you can build, and for a developer, FAR means profit.
In practice of course, it’s much messier: You can usually find out FAR, but it’s subject to lots of adjustments. And then, you also have to consider parking minimums, height restrictions, back yards, front lots, offsets, etc. Zoning is a huge set of constraints on what you can build, and once you apply all of this, there’s often not much freedom left for creative building shapes.