Code: ADU (Ancillary/Accessory Dwelling Unit)
Description: (Ancillary/Accessory Dwelling Unit) is a self-contained secondary housing unit on the same lot as a one- or two-family house. Accessory Dwelling Unit; City of Yes program for adding a small secondary home on the same lot
Practical Meaning: An ADU is a small extra home on the same lot as a 1- or 2-family house, such as a basement apartment, attic unit, garage conversion, or backyard cottage.
Where You May See It: In City of Yes housing materials, DOB and HPD program pages, zoning guides, and homeowner applications for new housing units.
Why It Matters: For NYC homeowners, ADUs may create legal extra living space and possible rental income, but they must follow city rules, safety requirements, and permitting steps.