New York City calls an accessory dwelling unit an Ancillary Dwelling Unit. The Department of Buildings (DOB) handles ADU job filings through DOB NOW: Build. The job type depends on how the unit relates to the building, and an approved job filing is followed by a separate permit request. Neither step by itself confirms that a property is eligible for an ADU.
Confirm the DOB job type
NYC DOB’s ADU FAQ describes an Alt-CO-GC filing when the ADU is within the same building. A detached ADU, or one separated by a firewall while on the same Building Identification Number (BIN), uses a New Building-GC filing. Confirm the building configuration and BIN with the design professional handling the plans and with DOB before submitting; the FAQ’s general categories do not assign the filing type for a particular property.
The ADU section appears in the PW1: Plan/Work Application tab. The applicant must answer whether the job scope includes an ADU and respond to the additional questions shown when the answer is yes. NYC DOB’s general filing guide explains that associated stakeholders need NYC.ID accounts to sign in to DOB NOW: Build.
Submit the job filing, then request the permit
Enter the job filing information and upload the plan sets and DPL1 document. DOB NOW may request other materials based on the filing information. The applicant, property owner, and other required stakeholders provide electronic attestations. Review the filing, pay the applicable amount, provide the final electronic signature, and submit it to DOB.
DOB staff review the job filing. If they issue objections, respond in DOB NOW and resubmit corrected information; an online meeting may be required to resolve an objection. Job-filing approval does not itself issue the construction permit. Submit the separate permit request, obtain the required stakeholder signatures, and respond to any permit-review objections. DOB’s general filing guide also directs applicants to resolve any applicable civil penalties for work without a permit before submitting the permit request.
Add the certificate for a basement or cellar ADU
For covered basement or cellar filings, NYC DOB added a closeout document requirement effective August 17, 2026. Its service notice says an approved Department of Health and Mental Hygiene (DOHMH) Radon and Vapor Level Certificate must be uploaded in DOB NOW before the Final Certificate of Occupancy can be issued. The notice applies to Alteration-CO and New Building job filings that include an ADU in a basement or cellar, including the specified case of an ADU in a newly erected one-family residence.
When completing PW1, answer Yes to the ADU question and select Basement or Cellar as its location so DOB NOW requests the certificate. The certificate records measurements within DOHMH limits and carries the required tester and environmental-professional certifications. Check the current DOHMH form, testing rules, filing applicability, and qualified-provider requirements with the City; the filing notice does not establish that a basement or cellar ADU is allowed at a particular property or that test results will pass.
Confirm the closeout path
When the permit is issued, associated stakeholders receive an email notification and can print the permit from DOB NOW. After the work, some applications require a new or amended Certificate of Occupancy, while others are signed off when the work is complete. Confirm which closeout applies to the approved job and keep the permit, inspection results, and final occupancy or sign-off record with the property documents.
NYC DOB’s filing pages do not provide an ADU-specific fee total or review-time estimate. Required documents, professional-certification eligibility, objections, building-code and zoning requirements, inspections, and closeout depend on the project and current DOB instructions. Use the general plans, inspections, and completion checklist for the broader submission-to-closeout questions.