Zoning Floor Area in NYC: What Counts and What Is Excluded

Zoning floor area is not the same as gross square footage on a plan, and the difference can be thousands of square feet on a mid-size building.

The basic definition

ZR 12-10 defines floor area as "the sum of the gross areas of the several floors of a building or buildings, measured from the exterior faces of exterior walls or from the center lines of walls separating two buildings." It is a gross number, not a rentable or usable number. Walls, shafts and corridors count unless the text specifically excludes them. Every FAR limit in the Zoning Resolution, and the unit count, applies to this number, so getting it right decides how much you can build.

Floor area ratio is total floor area on a zoning lot divided by its lot area. The definition's own example: a 10,000 sq ft zoning lot with 20,000 sq ft of floor area has an FAR of 2.0 (ZR 12-10).

What counts and what does not

Summary of the ZR 12-10 "floor area" definition, last amended December 5, 2024. The definition has more detail on parapets, railings and roofed terraces; read the full text before relying on a balcony or terrace exclusion.

Exclusions added for energy and housing

• Fully electrified or ultra low energy buildings: floor space equal to five percent of the floor area in the building is excluded. A "fully electrified building" is one existing on December 6, 2023 that meets Local Law 154 of 2021 as it would apply to new buildings (ZR 12-10).
• Qualifying exterior wall thickness: insulation added to a building existing on December 6, 2023, up to 12 inches, is excluded when it meets the R-value and other conditions in the definition (ZR 12-10).
• Rooftop greenhouses that qualify, and sun control devices that are inaccessible except for maintenance, are excluded (ZR 12-10).
• Tall-building stairs: in residential buildings over 125 ft developed or enlarged after April 16, 2008, up to eight inches of stair and landing width per floor can be excluded on stories with residences, if the stairwell is at least 44 inches wide and is a required means of egress (ZR 12-10).

New exemptions for apartment buildings (ZR 23-23)

City of Yes for Housing Opportunity added four exemptions for buildings containing multiple dwelling residences. They apply to buildings developed after December 5, 2024, and to newly created or altered space in existing buildings after that date (ZR 23-23).

• Amenities: up to five percent of the residential floor area of the building, for spaces such as recreation rooms, co-working areas, laundry, package rooms or pet facilities, accessible to residents. Circulation space does not count as amenity space (ZR 23-231).
• Corridors: 50 percent of a corridor can be exempted if it reaches outdoor space on a balcony or terrace, has daylighting through at least 20 sq ft of glazed windows, or ends at a unit with at least three bedrooms. Separately, 50 percent can be exempted if the corridor runs no more than 100 linear feet from the elevator core (or central stair) to the farthest unit door. The two can be combined (ZR 23-232).
• Refuse storage: up to three square feet per dwelling unit (ZR 23-233).
• Elevated ground floor units: up to 100 sq ft of entryway per foot of difference between the unit floor and curb level, with a maximum of 500 sq ft per building (ZR 23-234).

Exempted space still counts as floor area for other ground-floor rules, such as limits on floor area for certain uses and parking screening requirements (ZR 23-23).

A worked example

A 10,000 sq ft lot in an R7A district allows 40,000 sq ft of standard residential floor area (4.00 FAR, ZR 23-22) and 59 dwelling units (40,000 / 680 = 58.82, rounded up under ZR 23-52). Using the ZR 23-23 exemptions:

• Amenities: 5% x 40,000 = 2,000 sq ft exempt.
• Refuse rooms: 59 units x 3 sq ft = 177 sq ft exempt.
• Corridors: if each of 8 residential floors has a 600 sq ft corridor under 100 ft long, 50% of 4,800 sq ft = 2,400 sq ft exempt.
• Total exempt: 2,000 + 177 + 2,400 = 4,577 sq ft. The building could contain about 44,577 sq ft of above-grade space while still counting only 40,000 sq ft of zoning floor area, before cellar, mechanical space and the other 12-10 exclusions.

The corridor sizes are an illustration. Height and setback limits (ZR 23-43) still have to fit the whole building, exempt space included.

Where people go wrong

• Counting a basement as a cellar. The difference is whether more than half the height is below curb level (or the base plane): a cellar is excluded, a basement counts (ZR 12-10 "cellar" and "basement").
• Treating an attic as free space. Any attic area with 8 ft or more of structural headroom counts.
• Assuming enclosed balconies are free. Over 67 percent enclosure brings the balcony into floor area.
• Leaving out inaccessible space. Floor space that is made inaccessible counts unless otherwise exempt.

Floor area FAQ

Related pages

• Dwelling unit factor
• Community facility FAR
• What City of Yes changed
• R7A zoning
• R6B zoning