As of October 2026, ADU applications are filed through DOB NOW: Build, which opened for ADUs on September 30, 2025. An ADU inside the existing building is filed as an Alteration CO job; a detached ADU, or one separated by a firewall, is filed as a New Building job. Plans are prepared by a registered design professional.
What goes into the design?
- A survey and zoning analysis: district, lot lines, required yards and flood maps.
- Architectural plans meeting Appendix U of the Building Code.
- Sprinkler, egress and fire separation design.
- Utility plans, including shutoffs and disconnects for the ADU.
- For basements and cellars, water sensors and the DOHMH radon and vapor certification step.
Can I use a pre-approved plan?
Yes. DOB's Pre-Approved Plan Library holds designs submitted by licensed design professionals and reviewed by DOB in advance. Each approved plan gets a Pre-Approved Plan Number, and homeowners can hire the professional who created it. Site-specific items still need review.
Can the filing be self-certified?
DOB's FAQs say professional certification is allowed for ADU filings, except for units in the Local Law 126 legalization pilot, which DOB's Central Development Unit reviews.
What does the certificate of occupancy say?
DOB requires the CO to note the unit as an "Ancillary Dwelling Unit per ZR 12-10 and BC Appendix U." The schedule of occupancy lists the ADU under R-2 or R-3, and cellar ADUs are labeled "ADU Apartment U."
Who is licensed to build it?
New York City licenses home improvement contractors through the Department of Consumer and Worker Protection, and the Department of Buildings registers general contractors for new building and major alteration work. ADU Craft New York is licensed and insured; we provide license and insurance details in writing with your quote.