Mayor Zohran Mamdani on Wednesday is set to announce plans to expand and accelerate accessory dwelling units in New York City — sometimes called granny flats — aimed at helping homeowners to garner extra rental income and stay in their longtime neighborhoods.
Mamdani’s plans include an online library of pre-approved ADUs, a cost-estimator, tools to cut red tape, financing up to $395,000, and a website called ADU for You.
Among the potential locations for an ADU, also called an ancillary dwelling unit: basement apartments, attic conversions, an attached addition, a detached backyard unit or a converted garage, according to the website.
“One of the solutions to the housing crisis can be found in our backyards, our attics, or our basements — in an Ancillary Dwelling Unit. That’s why our administration is making it easier and more affordable to build an ADU through a library of pre-approved plans and new financing options,” Mamdani said in a news release.
Later Wednesday, Mamdani is scheduled to visit an ADU.
This ADU (ancillary dwelling unit), which would go above a new or existing garage, is one of several offered in an online library New York City is announcing Wednesday. Credit: NYC Housing Preservation & Development
“By making it easier for New Yorkers to turn their homes into an extra place for a loved one or a little more income, we’re allowing our city to grow while keeping the character of the neighborhoods we love.”
ADUs have sometimes been resisted by municipalities on Long Island over concerns such as parking, increased housing density and other quality-of-life issues.
In 2022, Gov. Kathy Hochul tried, and failed, to pass legislation to incentivize municipalities to allow ADUs to be built in neighborhoods zoned for single families.
But a statewide program known as Plus One ADU that aims to curb the affordable housing shortage offers low to moderate-income Long Island homeowners in some towns up to $125,000 in a forgivable loan to build or retrofit accessory dwelling units.
Newsday has reported that Long Island buyers are starting to look for properties with the ADUs — or the prospect of building one — when looking for a home. It’s a trend seen across the United States, according to the Zillow Consumer Housing Trends Report of 2025.
Having a property with a backyard cottage, basement apartment or garage conversion will lead to a lending institution like a bank considering the projected rental income to help a prospective mortgage seeker qualify, real agents told Newsday.
In New York City, Leila Bozorg, Mamdani’s top deputy for housing and planning, said that the new plan should help anyone who wants to add an ADU.
“In the midst of a dire housing crisis, ADUs are an important tool for homeowners to add space, bring in extra income, and stay in their communities — but creating an ADU can feel out of reach for too many New Yorkers,” she said in a news release. “Whether you are interested in adding a new backyard cottage or converting an underused garage or attic into housing, we have resources to help guide you through the process.”
The city is behind Boston, Seattle, Washington, D.C., and other big cities by permitting only a fraction of the housing that these cities do, despite ballooning demand, according to a report by the Pew Charitable Trusts.
The Island is doing worse when it comes to building housing to meet demand: Among the United States’s top 100 largest counties, Suffolk and Nassau permitted less housing per capita from 2013 through 2022 than all but a single county, in Ohio, according to Bloomberg News.
Matthew Chayes, a Newsday reporter since 2007, covers New York City.