New York, NY Accessory Structures: ADU Rules (2026)

The New York City Zoning Resolution defines an ancillary dwelling unit in Section 12-10 as "an additional dwelling unit, permitted on the same zoning lot as a single- or two-family residence that does not exceed eight hundred square feet of floor area." Only one ADU is permitted per single- or two-family residence on a zoning lot, and at the time of initial occupancy the zoning lot must be the primary residence of an owner of such lot. The framework was created by the City of Yes for Housing Opportunity zoning text amendment adopted by the City Council on December 5, 2024, together with Local Laws 126 and 127 of 2024 amending the Administrative Code and Building Code (new Appendix U). ADUs may be created as conversions of existing space (a portion of the home, an attached or detached garage, or a basement/cellar), as additions to the home, or as new detached backyard cottages. Bulk rules in Article II Chapter 3 limit a detached building containing an ADU (including one over an accessory parking space) to two stories or 25 feet above adjoining grade, whichever is less, including the apex of a pitched roof; the building footprint may not exceed one-third of the rear yard or rear yard equivalent; a free-standing ADU building must be set back at least five feet from a rear or side lot line; and a minimum distance of 10 feet must be maintained between residences and the ADU on the same zoning lot. Building Code Appendix U (Section U202.3) prohibits basement and cellar ADUs within FEMA Special Flood Hazard Areas, the 10-year rainfall flood risk area, and the coastal flood risk area, and Appendix U Section U202.5 requires a minimum 7-foot clear ceiling height for habitable rooms in basements and cellars.