Adding an Ancillary Dwelling Unit ADU

Local Law 127 of 2024, enacted by the New York City Council, amends the Building Code and Fire Code to facilitate the creation of ancillary dwelling units (ADUs) in one- and two-family homes. This law is part of a broader initiative to expand affordable housing by making it easier for homeowners to develop legal secondary housing units.

Background and Legislative Context

In December 2024, the NYC Council passed zoning reforms projected to create over 82,000 new homes over 15 years. A major component of these reforms was legalizing and regulating ADUs, which include basement apartments, garage conversions, and backyard cottages. Local Law 127 corresponds to Introduction 1128-A, which sets eligibility, safety, and design requirements for these units.

Key Provisions of Local Law 127

Eligibility and Safety Requirements

• Certificate of Occupancy: Each ADU must have a separate certificate of occupancy from the primary dwelling unit to ensure compliance with habitability and safety standards.
• Size Requirements: ADUs must have a minimum size of 200 square feet, following New York State guidelines.
• Fire Safety and Habitability: ADUs must include:
  • Proper fire-resistant materials and smoke detectors
  • Adequate egress (emergency exits)
  • Independent utility connections (water, gas, electricity)
  • Proper ventilation, lighting, and ceiling height to ensure livability
• Flood Hazard Area Restrictions: The construction of basement and cellar ADUs is prohibited in coastal and inland flood zones to mitigate flood risks.

Implementation and Support

The Department of Housing Preservation and Development (HPD) is responsible for assisting homeowners with:

• Navigating the ADU approval process
• Ensuring compliance with design and safety standards
• Providing technical guidance on retrofitting existing spaces

Anticipated Impact

This law aims to:

• Increase affordable housing options in NYC
• Provide supplemental income opportunities for homeowners
• Support multigenerational living and diverse community growth

Conclusion

Local Law 127 of 2024 is a crucial step in addressing NYC’s housing crisis by legalizing and regulating ADUs. By ensuring clear safety standards and streamlined approval processes, the city hopes to expand housing supply while maintaining resident safety and neighborhood integrity.