How to Get Started Adding an Accessory Dwelling Unit in New York City

Thinking about adding an Accessory Dwelling Unit (ADU) in New York City?

Thanks to the new City of Yes for Housing Opportunity changes, building an ADU is more accessible than ever. But there are important steps and requirements to keep in mind.

First, check that your property meets all zoning requirements. The updated rules especially benefit owners of one- and two-family homes, making it easier to add an ADU. You’ll need to design your unit to meet specific size and safety standards, work with a registered architect or engineer to file plans with the Department of Buildings (DOB), and secure all necessary permits before building begins. Plus, programs like the Plus One ADU Program might offer financial help for eligible homeowners.

Here’s a step-by-step guide to get you started:

• 1. Understand the rules and eligibility:
  
  
  • Zoning: Confirm your property is zoned for an ADU and your project fits the City of Yes for Housing Opportunity rules, which apply to new ADUs in one- and two-family homes. For a general overview, see this guide.
  
  
  • Size limits: ADUs must be no larger than 800 square feet or 40% of your home’s habitable floor area—whichever is smaller. Detached backyard cottages also can’t exceed one-third of the required rear yard.
  
  
  • Owner-occupancy: Either you or your tenant must live in the primary home or the ADU as your main residence.
  
  
  • Two-family homes: If you own a two-family home, you can add one ADU. However, this might mean you’ll need to comply with the Multiple Dwelling Law (MDL), which could require additional safety upgrades for the whole building.
  
  
  • Legalization: If you’re looking to legalize an existing unit, the process is different. Check out the DOB’s Basement Legalization program for specific guidance.

• • 2. Design and plan your ADU:
    
    
    • Hire a professional: A registered architect or engineer is required to design your ADU and submit plans to the DOB.
    
    
    • Meet code requirements: Your ADU must follow all NYC building and zoning codes, including rules for ceiling height, fire safety, and emergency exits. More details can be found here.
    
    
    • Choose a location: ADUs can take many forms, such as basement apartments, attic conversions, or backyard cottages. Pick the option that best fits your property and needs. For inspiration, check out this article or watch this video.

• 3. File for permits:
  
  
  • Log in to DOB NOW: Your registered architect will access the DOB NOW system to create and submit your filing.
  
  
  • Complete the PW1: The Plan/Work Application (PW1) now includes a section to indicate if your project involves an ADU.
  
  
  • Answer additional questions: When prompted, answer “Yes” to the ADU question, and provide the pre-approved plan number and ADU location as required.

• 4. Explore financial assistance:
  
  
  • Plus One ADU Program: See if you qualify for low- or no-interest loans and construction grants through this Department of Housing Preservation and Development (HPD) program. Find more details in the official FAQ.
  
  
  • ADU For You Program: NYC also offers this program to provide guidance, design support, and helpful resources for homeowners building ADUs. Learn more here.

For more information and updates, you can always check the City’s official resources or consult with a local professional who specializes in ADUs. You can also explore additional details and examples at these useful links:

• ADU Regulations in New York

• How NYC Homeowners Can Now Apply to Build ADUs

• City of Yes Housing Opportunity Guide (PDF)

• ADU Information Video

• Croton-on-Hudson ADU Resources

• NYC DOB: Types of ADUs

• General ADU FAQ (PDF)