NYC ADU Permit Process

Verify your property is eligible for an ADU by checking zoning district, lot size, building type, and any overlays (flood zones, historic districts). You can use the free tool on nycadu.com or HPD’s online eligibility screener.

Engage a NYS-licensed Registered Architect (RA) or Professional Engineer (PE) to design your ADU. You can save significant time and money by using HPD’s Pre-Approved Plan Library (PAPL) instead of a fully custom design.

Conduct a property survey, soil/geotechnical testing, and for basements, radon and chemical vapor testing. These reports inform the structural and foundation design.

The NYC Department of Environmental Protection (DEP) must certify that the local sewer system has capacity for your new unit. Your PE or RA files this on your behalf.

Submit your application through the DOB NOW: Build portal. Basement and garage conversions use the Alt-CO-GC (Alteration CO – General Construction) work type. New detached ADUs file as a New Building application.

DOB examiners review your plans for code compliance, zoning conformance, and structural adequacy. Pre-approved plans undergo a streamlined review that cuts the timeline roughly in half.

After plan approval, obtain your work permit and begin construction. You’ll need a licensed General Contractor (GC) and potentially separate permits for plumbing, electrical, and mechanical work.

DOB inspectors visit at key milestones: foundation, framing, rough-in (plumbing/electrical/mechanical), fire safety systems, and a final inspection. All must pass before you can get your Certificate of Occupancy.

After all inspections pass, DOB issues an updated Certificate of Occupancy reflecting the ADU. This is the final legal step—without it, you cannot legally occupy or rent the unit.