NYC ADU Rules After City of Yes

The Zoning Resolution calls them "ancillary dwelling units." Here is every rule we found in the adopted text, with the section it comes from.

What counts as an ADU

• An "ancillary dwelling unit" is an additional dwelling unit on the same zoning lot as a single- or two-family residence, and it cannot exceed 800 sq ft of floor area (ZR 12-10).
• Only one is allowed for each single- or two-family residence on the zoning lot (ZR 12-10).
• DCP lists the forms it can take: backyard cottages, garage conversions, basement apartments and enlargements of the existing building, either from existing space or as new construction (DCP ADU guide).
• DCP's handout covers new ADUs; existing units seeking legalization are subject to different rules (DCP ADU guide).

Where ADUs are not allowed

Where backyard ADUs are banned, the rule does not legalize an existing structure that sat in a required yard or open space before December 5, 2024 (ZR 12-10).

Owner occupancy

When the ADU is first occupied, the zoning lot must be the primary residence of an owner of that lot (ZR 12-10). DCP's handout puts it simply: homeowners must live at a property to build an ADU there.

Backyard ADUs: height, size and spacing

• A backyard ADU can sit in the required rear yard as a permitted obstruction. For an ADU tied to a detached, zero lot line or semi-detached house, it is limited to one story and 15 ft at any level (ZR 23-341).
• If a parking space is provided below the ADU, the structure can reach two stories or 25 ft above adjoining grade, whichever is less, including the peak of a pitched roof (ZR 23-341).
• The structure can cover no more than one-third of the rear yard (or rear yard equivalent) (ZR 23-341).
• If it stands apart from other buildings, it must be at least 5 ft from the rear and side lot lines (ZR 23-341).
• It must be reachable directly from a side yard or an open area along a side lot line at least 5 ft wide (ZR 12-10).
• The minimum distance between the main house (two or fewer units) and an ADU on the same lot is 10 ft (ZR 23-371).

Parking

No parking is required for an ADU. In the Inner Transit Zone no parking is required for any new dwelling unit (ZR 25-211); in the Outer Transit Zone and beyond the Greater Transit Zone the parking table sets the requirement for an ADU at 0% (ZR 25-222, 25-232).

Floor area: will it fit?

We found no separate floor area allowance for ADUs in the residential bulk rules (Article II, Chapter 3), so plan on the ADU's floor area counting toward the lot's maximum floor area. On a 40 x 100 ft lot in an R4 district (1.00 FAR for a standard lot under ZR 23-21), the lot allows 4,000 sq ft in total; if the house already uses 2,400 sq ft, up to 800 sq ft remains, which an ADU at the size cap would use up. Lots in R3 and R2 districts start at 0.75 FAR, so a large existing house can leave little or no room.

One more R1 to R5 limit: on standard lots of 4,000 sq ft or more, the floor area tied to any single dwelling unit cannot exceed 0.60 FAR (ZR 23-21, note 1).

A quick checklist

• Is there a single- or two-family residence on the lot?
• Is the lot in a mapped flood-risk area, a historic district, or an R1-2A, R2A or R3A district outside the Greater Transit Zone?
• Is there enough unused floor area for up to 800 sq ft?
• For a backyard unit: does a 15 ft, one-story structure fit within one-third of the rear yard, 5 ft from lot lines and 10 ft from the house, with a 5 ft path from the side?
• Will an owner live on the lot when the ADU is first occupied?

Building and housing codes (egress, ceiling height, fire separation) also apply and are outside the Zoning Resolution. Zohgo's free check gives you the zoning numbers for a specific address.

ADU FAQ

Related pages

• What City of Yes changed
• Parking after City of Yes
• R4 zoning
• R5 zoning
• Blog: can you build a backyard ADU?