Ancillary Dwelling Unit (ADU)
City of Yes: Ancillary Dwelling Units (ADUs)
Under the City of Yes for Housing Opportunity (adopted on 12/5/24), New York City significantly expanded where and how Ancillary Dwelling Units (ADUs)—also referred to as accessory dwelling units—are allowed, making it easier to add small, independent housing units within existing buildings or on zoning lots.
Core ADU rules (City of Yes)
-
Where allowed: ADUs are permitted on the same zoning lot as a 1- or 2-family home (the City of Yes ADU framework).
-
How many: 1 ADU max per 1- or 2-family residence on a zoning lot.
-
Owner occupancy: At initial occupancy, the zoning lot must be the primary residence of an owner of that lot.
-
Size cap: ADU is up to 800 sq ft of zoning floor area.
-
Separate entrance: ADUs must have a separate entrance (from the exterior or a public corridor).
-
Building/code compliance: ADUs must generally comply with NYC Building Code Appendix U (created specifically for ADUs), plus standard code items like egress and life safety.
What counts as an ADU type
City/agency guidance describes ADUs including:
-
Backyard cottages (detached)
-
Garage conversions (attached or detached)
-
An attached addition
-
Basement / attic units (subject to specific code and limits—see exceptions below)
Grants and low-interest loans may be obtained by eligible home owners.
More information about eligibility, requirements, and the application process can be found here:
https://www.nyc.gov/site/hpd/services-and-information/plus-one-adu.page