Zoning, FAR and Air Rights on an NYC Lot

A lot's zoning district sets how much floor space can be built on it, expressed as a floor area ratio (FAR): the maximum FAR times the lot area gives the most floor area zoning allows. If a building has less floor area than that, PLUTO data will show a gap often called "unused development rights," but height limits, lot shape, landmarks, tenants and the existing building usually decide whether anything bigger can actually go up.

Reading a zoning district code

New York City is divided into three basic kinds of zoning districts: Residence (R), Commercial (C) and Manufacturing (M). The PLUTO data dictionary lists residence districts from R1-1 to R12, commercial from C1-6 to C8-4 and manufacturing from M1-1 to M3-2, plus mixed manufacturing-residential districts written like M1-1/R5. As a rule, the higher the number right after the letter, the denser the district.

• Suffix letters such as A, B, D or X (R6A, R7X) mark versions of a district with their own height and bulk rules.
• Commercial overlays (codes starting C1 or C2) are mapped on top of residence districts, to serve local retail needs such as grocery stores, dry cleaners and restaurants. PLUTO stores them in separate overlay fields.
• Special purpose districts add rules for an area and appear in PLUTO's special district fields.

Roofy shows the main district under Building details on each building page. That is PLUTO's Zoning District 1: the district covering the largest share of the lot. If a zoning line splits the lot, up to three more districts are listed, each only if it covers at least 10% of the lot. For the full picture, including overlays, special districts and pending rezonings, check the lot on City Planning's ZoLa map.

What floor area ratio means

The Zoning Resolution defines floor area ratio as the total floor area on a zoning lot divided by the lot area. Its own example: a 10,000-square-foot zoning lot with a 20,000-square-foot building has a FAR of 2.0, and so does a 20,000-square-foot lot with two buildings totaling 40,000 square feet. FAR caps total floor space, not height or footprint, so the same FAR could be a squat building covering the lot or a slimmer, taller one, within the district's other limits.

"Floor area" in zoning is a specific measure: the gross area of each floor measured from the exterior walls, including things like elevator shafts and stairwells at each floor and some attic and basement space, with listed exclusions.

R1 to R5 districts have their own rules in §23-21, and commercial and community facility uses have separate FAR limits. Some districts, such as R6, R7-1, R7-2 and R8, have different numbers depending on whether the lot is within 100 feet of a wide street, which is why we left them out of the table. Always read the current section for the exact district.

The FAR fields in PLUTO

Worked example: a three-family house in an R6A district

Here is the arithmetic for a real lot, BBL 3016170081 (925 Greene Avenue, Brooklyn), using its PLUTO 26v2 record:

1. 1

   Lot area: 1,440 sq ft

   An 18-by-80-foot lot. PLUTO lists the zoning as R6A, with no split and no overlay.
2. 2

   Built: 2,160 sq ft, FAR 1.50

   2,160 ÷ 1,440 = 1.50. A two-story, three-family walk-up (building class C0).
3. 3

   Zoning maximum: FAR 3.00 = 4,320 sq ft

   ResidFAR is 3.00 for standard housing, matching R6A in §23-22. 3.00 × 1,440 = 4,320 sq ft.
4. 4

   Gap on paper: about 2,160 sq ft

   4,320 − 2,160. With qualifying affordable housing, AffResFAR of 3.90 would allow 5,616 sq ft, a gap of about 3,456 sq ft.
5. 5

   Now apply reality

   Building area in PLUTO is an estimate, the R6A height limit and yard rules still apply, and three households live there. An architect’s zoning analysis is the only way to know what could actually be built.

What "unused development rights" can and can't mean

The gap between built and allowed FAR is a ceiling, not a promise. Things that often stop it from turning into a bigger building:

• Other bulk rules. Height limits, setbacks, yards and lot coverage can make the maximum FAR impossible to reach on a narrow or shallow lot. The data dictionary itself warns that ResidFAR in some districts assumes ideal conditions.
• Zoning lots aren't tax lots. Zoning counts floor area on the "zoning lot," which the Zoning Resolution says may or may not match the tax lot. Two neighboring tax lots may already be one zoning lot, with the floor area shared.
• Landmarks and historic districts. Designated buildings and historic districts come with Landmarks Preservation Commission oversight that can limit additions; Roofy shows landmark and historic district status under Building details.
• The existing building and its tenants. Adding floors to an occupied building is expensive, and rent-regulated tenants have legal protections.
• Rezonings and text changes. The numbers change when the City amends the Zoning Resolution or remaps an area. Section 23-22, for example, was last amended on December 5, 2024, so older articles quoting FAR figures may be out of date.

How air rights move between lots

"Air rights" is the everyday name for unused floor area. In general they can only be used on the same zoning lot. Two common ways that changes:

• Combining lots into one zoning lot. Under the Zoning Resolution's zoning lot definition, lots on the same block that touch for at least 10 linear feet can be declared one zoning lot through a written Declaration of Restrictions signed by each party in interest and recorded with the City Register. Once merged, floor area counts across the combined lot, which is how a new building can use a neighbor's unused floor area. Those declarations are public records; see how to search ACRIS.
• Landmark transfers. Section 75-42 of the Zoning Resolution sets rules for moving unused floor area from a designated landmark (the "granting lot") to a "receiving lot" nearby, and Section 74-79 lets the City Planning Commission approve larger transfers and related bulk changes by special permit. Some special districts have their own transfer rules.

For homeowners, the more practical question is often whether you can add a unit rather than a floor. City of Yes rules on accessory units are covered in adding an ADU in NYC, and permits in do you need a DOB permit?

How to check a lot yourself

1. Look up the address on Roofy and note the zoning district, lot area, building area and landmark status.
2. Open the lot on ZoLa to see overlays, special districts, split lots and recent rezonings.
3. Read the district's section of the Zoning Resolution for FAR, height and yard rules.
4. Search ACRIS for zoning lot declarations or development rights agreements recorded against the lot.
5. For any real decision, such as buying a site or planning an addition, hire an architect or zoning attorney.

For how PLUTO measures lot and building area in the first place, see PLUTO data fields explained.