The NYC ADU Permit Process: Step-by-Step Guide for Homeowners
Have extra space on your property? A basement, garage, or even a backyard? If so, you may be eligible to build an Accessory Dwelling Unit (ADU), as they just became legal in NYC.
That’s right, you can legally build a second, smaller home on your property. Maybe it’s for your aging parents. Maybe it’s to earn extra rental income. Or maybe it’s just time to create some breathing room in today’s housing market.
This guide will walk you through the entire process, step by step.
Ready to see if an ADU makes sense for you? Let’s dive in.
Step 1: Is Your Property Even Eligible?
Under NYC’s new ADU regulations, one ADU per property site is permitted, and it must be on a single- or two-family home. If you happen to own a three-family brownstone or a six-unit walk-up, you’re out of luck (for now).
Next, check what zoning district you’re in. Residential zones differ, some permit ADUs outright, others require special permits or variances. A few minutes on the phone with your local borough office or a look at the NYC Zoning Map can save you months of heartbreak, but if you want to be absolutely certain, consider hiring an NYC ADU or NYC zoning code expert.
This is the feasibility stage and it’s the one most people skip, only to regret it later.
Step 2: Bring in the Pros (Yes, Really)
You might be handy, maybe you’ve built a bookshelf or two, but an ADU project runs best with a licensed architect or designer by your side.
And it isn’t just what’s best - it’s required to hire a licensed architect or designer to create your plans for the the NYC Department of Buildings (DOB). They require professional drawings that include:
Floor plans
Zoning and building code compliance
Exterior elevations
Site layout showing setbacks
Structural and mechanical details
Step 3: File Your Plans with the DOB
When your plans are ready, file them with the Department of Buildings. This isn’t just emailing a PDF, it’s a formal filing process that includes:
Completing the proper application forms
Paying filing fees (based on project size)
Ensuring plans comply with all NYC building, zoning, and fire codes
If your paperwork isn’t perfect the first time, the process can take weeks or even months. Even licensed architects make mistakes sometimes. That’s why it’s important to make sure you have an experienced DOB permit expeditor or filing representative on your side.
Tip: Ask your architect to explain their DOB filing process. Some firms have in-staff permit expeditors, while others use third-party expeditors who maintain established relationships with DOB reviewers that can speed up approval time.
Step 4: Get Your Permits
After DOB approval, you’ll be issued your final construction permits. Do not begin construction until this happens. Even if your neighbor did. Even if your contractor says, “It’ll be fine.”
Building without a permit in NYC can result in fines, stop-work orders, or even demolition of your new structure. Your permits will dictate what’s allowed and which inspections you’ll need along the way.
Step 5: Build It (The Fun Part!)
Now the sawdust flies and your vision becomes reality.
But even during construction, the city is watching. You’ll need to schedule required inspections at the foundation, framing, plumbing, electrical, and final sign-off stages. Miss one, and your Certificate of Occupancy (CO) will be delayed.
Stay in close contact with your contractor and architect. They’re responsible for scheduling inspections, but it never hurts to supervise the supervisor.
Step 6: Pass Final Inspection & Get Your Certificate of Occupancy
The finish line. Once the last nail is in and the final coat of paint has dried, the DOB will schedule a final inspection.
If everything matches your approved plans and complies with code, you’ll receive your Certificate of Occupancy, the golden ticket confirming your ADU is a legal, habitable dwelling unit.
Final Thoughts
From the first sketch to the final certification of occupancy, the process can take 6–24 months, especially if you’re part of the city’s Plus One ADU Program, which includes extra steps like online surveys and waitlists.
Here’s the silver lining: every day you wait is one day closer to more space, more income, and more security.