What are air rights in NYC?

Air rights are floor area, not air

The phrase suggests a slice of sky, but nothing in the Zoning Resolution sells space above a roof. What changes hands is permitted floor area. ZR 12-10 defines floor area ratio as the total floor area on a zoning lot divided by the lot area of that zoning lot, and each district sets a maximum FAR. A 10,000 sf zoning lot with a 20,000 sf building has an FAR of 2.0; the Resolution uses that very example.

So the arithmetic is simple. Maximum floor area = lot area × maximum FAR. Unused floor area = maximum floor area minus the floor area of the buildings already on the zoning lot. When people say a church or a low walk-up “has air rights,” they mean that second number is large.

Floor area itself has a precise meaning. ZR 12-10 counts the gross area of each floor measured from the exterior faces of exterior walls, and then excludes specific spaces, including cellar space not used for dwelling purposes, elevator and stair bulkheads, and attic space with less than eight feet of structural headroom. Two buildings with the same gross size can therefore use different amounts of zoning floor area.

Everything is measured on the zoning lot

A tax lot is a line on the Department of Finance map. A zoning lot is what the FAR applies to, and the two do not have to match. Under ZR 12-10 a zoning lot is one of four things:

• ■(a) a lot of record that existed on December 15, 1961, or on the date of a later applicable amendment;
• ■(b) a tract of one or more contiguous lots of record within a single block that was in single ownership on that date;
• ■(c) a tract of lots of record contiguous for at least 10 linear feet, within a single block, in single fee ownership when the building permit is filed, with every party in interest joining; or
• ■(d) a tract of lots of record contiguous for at least 10 linear feet, within a single block, declared to be one zoning lot in a recorded Declaration of Restrictions executed by each party in interest.

Paragraph (d) is the zoning lot merger, and it is how most air rights move between neighbors. The Resolution says it plainly: a zoning lot may or may not coincide with a lot on the official tax map. Part 2 of this series, how a zoning lot merger moves air rights, walks through the documents.

A worked example on a real lot

A real lot from RunEnvelope's published lot pages: 3918 4 Avenue, Brooklyn, zoned R7A. The figures below are the ones printed on that page.

How to tell whether a lot has air rights

1. 01

   Find the lot area and the district

   City Planning's PLUTO file and the ZoLa map give the lot area, the zoning district, any commercial overlay and any special district. The lot test on this page reads them for you.
2. 02

   Look up the FAR for the use

   Residential FAR in R6 through R12 is in ZR 23-22, with a separate, higher column for qualifying affordable or senior housing; R1 through R5 are in ZR 23-21. Commercial, community facility and manufacturing FARs have their own tables, and special districts can override all of them. The FAR calculator and the district pages list them.
3. 03

   Subtract what is built on the whole zoning lot

   Use the floor area of every building on the zoning lot, not just the one you are looking at. If the lot was merged with a neighbor years ago, the neighbor's building counts, and so does any floor area already transferred away. Neither shows up on a tax map; the recorded declarations in ACRIS do.
4. 04

   Check that someone can actually build it

   Unused floor area only has value if a building can hold it. Yards, height limits, setbacks and lot coverage decide that, which is why Part 7, when lot area × FAR overstates what you can build, exists.

Three ways air rights move

• ■Zoning lot merger. Adjacent lots on the same block become one zoning lot under ZR 12-10 (c) or (d). The FAR then applies to the combined lot area and the floor area can be placed anywhere on it, subject to every other rule.
• ■Landmark transfer. A designated landmark can transfer unused floor area by certification to lots on its block or across a street or street intersection from that block, under ZR 75-42, with a cap on how much any receiving lot gains. Part 5 covers it.
• ■Special district transfers. East Midtown, the Theater Subdistrict, West Chelsea's High Line Transfer Corridor and Hudson Yards each have their own granting and receiving rules. Also Part 5.

Where the simple number goes wrong

• ■Overbuilt lots. A building older than the current rules can hold more floor area than the FAR now allows. Its unused floor area is zero or negative, and merging it into your zoning lot uses up your rights instead of adding to them.
• ■Split districts. Where a zoning lot spans two districts, ZR 77-22 weights each district's FAR by the share of the lot in it. The blended figure is the cap, not the higher of the two.
• ■Bonus floor area. The higher FAR for qualifying affordable housing in ZR 23-22 exists only for a project that provides it, and a landmark's transferable amount under ZR 75-422 excludes bonus floor area altogether.
• ■Rights already sold. A previous merger or transfer is recorded against the lot, not shown in PLUTO. Read the lot's recorded documents before quoting a number.