In his ambitious recent citywide Block by Block housing program, Mayor Mamdani pledged to “expand opportunities for homeowners to add accessory dwelling units and legalize basement apartments safely.”
Mamdani may think he’s a housing pathbreaker — but he’s echoing both his two immediate predecessors. In 2019, Bill de Blasio said “there are thousands of basement apartments in our city, but too many are illegal and unsafe.”
In 2025, Eric Adams decried the fact that “too many New Yorkers have been forced into dangerous basement and cellar set-ups just to find a place to live” and pledged to turn illegal, unsafe apartments into “legal, safe ones.”
Perhaps Mamdani will be more successful in this mission — but there’s a reason that so many dangerous basement units continue to exist: the city’s requirements to make them legal are too stringent and therefore too costly.
To make a basement unit comply with city building codes, not only must it have two ways to get out in case of fire or flood — by far the most important need — but every room must have at least a seven foot ceiling. Bedrooms must be 70 square feet — and only one family can occupy the unit. No boarders such as unrelated roommates. Each room must have a window.
A small windowless bedroom might not be desirable for many renters — but for thousands of New Yorkers it’s already their means of obtaining affordable housing. Many pay the bills thanks to roommates.
As it stands, the steps to comply with the building code to legalize basement units is costly.
A realtor in Brooklyn’s Sunset Park section reports that 30 clients have asked him about legalization—and none has followed through. You’re talking about a multi six-figure job,” says Joseph Ranola: “Zero of my clients have followed through.”
Make no mistake, the stakes are high.
Basement apartments continue to be the sites of tragedy. An early morning fire on Aug. 27 in Ozone Park that injured two firefighters and spread across the 110th Ave. block. A 91st Ave. Jamaica resident who escaped a lithium-ion battery fire by climbing out a window, but died in the hospital.
This summer’s flash floods bring to mind the deaths of 13 in Brooklyn and Queens during Hurricane Ida in 2021 — when they drowned in their own apartments that had flooded.
The city to date has taken ineffective steps toward legalization.
In the waning days of the Adams administration, the city passed Local Law 126 — to establish the rules for “a pilot program to allow for the safe, temporary occupancy of certain basement or cellar apartments while those units are brought into compliance with applicable legal standards.”
The idea was to make it clear what steps an owner must take toward legalization and even held out a potential $125,000 city grant to cover the costs.
But laws don’t matter without specific rules to implement them. The Department of Buildings, says it “has not yet finalized the proposed rule for legalizing occupancy of existing non-compliant” dwelling units — despite the fact that public hearings concluded in December.
The right set of rules would focus on just the essentials: a second exit (even if that’s just a fire escape ladder attached to a window), as well as smoke and carbon monoxide detectors.
It would be nice to think that the city could pay to bring all the basement units up to code — but even if a $125,000 grant were enough to do so, that would mean $12 billion in city grants to cover 100,000 units. Better to support the minimal upgrades — that would be enough to save lives.
Mamdani has set out the right goal in promising to make basement apartments safe. He can fulfill his promise if his Buildings Department rule focuses on the most important thing: safety.
Husock is a senior fellow at the American Enterprise Institute.