A City Council panel advanced on Tuesday legislation that makes official the legalization of ancillary dwelling units (ADUs), such as “tiny houses” and basement units, for addition to new or existing homes.
The Committee on Housing and Buildings, chaired by Bronx Council Member Pierina Sanchez, voted unanimously on March 9 to approve Intro 421-A as a technicality required to align with the rezoning package collectively known as City of Yes for Housing Opportunity, which passed in December 2024. Intro 421-A was introduced to the full council on March 10.
ADUs were not part of the city’s housing code until City of Yes, which opened the pathway to legalize ADUs in certain non-flood-prone areas, provided they meet certain requirements. These include a maximum size of 800 square feet and having a separate entrance from the main home.
Though ADUs would still be relatively rare under the expansion, proponents say they could offer some relief from the housing shortage by providing a cost-effective option for seniors and young adults, for example, and creating a revenue stream for homeowners.
Under City of Yes, approximately 25,000 ADUs, whether tiny houses, attic or basement units, or garage conversions, could be added across the city in the next 15 years, according to an HPD estimate.
“The Council’s landmark 2024 City for All housing package — which secured more than $5 billion in housing investments — and the City of Yes zoning reforms allowed us to build a little more housing in every neighborhood,” said Sanchez in a statement.
“Those reforms legalized ancillary dwelling units like basement apartments, and Int. 421-A simply aligns the Housing Maintenance Code with those changes so basement apartments in newly built one- and two-family homes can be safely rented.”
Though ADUs have been illegal, some homeowners rented their extra spaces anyway, often creating safety hazards. For instance, thirteen New Yorkers died in flooded basement apartments during Hurricane Ida in 2021.
Under the new ADU program, homeowners seeking to build would be subject to stringent safety and occupancy requirements, and those with illegal basement units will have a pathway to bring them into compliance.
The bill now advances to Mayor Zohran Mamdani’s desk for his signature.
Reach Emily Swanson at eswanson@schnepsmedia.com or (646) 717-0015. For more coverage, subscribe to our newsletter and follow us on Twitter, Facebook and Instagram!
