Affordable Housing

Telltale signs that a NYC basement apartment is a legal rental

  • The windows on the ground level are at least 50 percent above grade
  • There are two ways out in case one exit is blocked by a fire
  • The CO can be confirmed via the DOB’s Building Information System
By Jennifer White Karp  |
June 11, 2024 - 12:30PM
Brownstone ground floor apartment

One way to tell if a basement apartment is legal is to check if 50 percent of the height of a ground floor is above street level. 


When Hurricane Ida blew through New York City in September 2021, it dumped more than half a foot of rain on Central Park in just a few hours, floated cars down city streets, and halted the subway system. At least 11 people were killed when their basement-level apartments filled with water or suffered other storm-related destruction.

The storm cast new attention on the problem of basement apartments–and the city's lack of progress so far to bring these units up to code and make them safe for living. Bringing basement apartments up to code is part of Mayor Eric Adams's City of Yes citywide rezoning proposal.

Not all basement apartments in NYC are illegal or unsafe, but you need to check them out carefully—or you could find yourself evicted after a surprise inspection—or the victim of a more tragic situation. Here’s how to tell if a basement apartment is legal. (And you can read more on how to avoid renting an illegal apartment and the pros and cons of living in a basement apartment.)

[Editor's note: A previous version of this post was published in March 2023. We are presenting it again with updated information for June 2024.]

Basement or cellar? 

In NYC, basements and cellars are not the same thing, and the difference determines whether a unit is a legal dwelling. According to the Department of Housing, Preservation & Development, a basement has at least half of its height above curb level, while a cellar is less than half above grade. 

This is one of the most obvious ways to tell whether a basement apartment is legal: Look at the ground-level of a building and check whether 50 percent of it is above grade. 

Generally, cellars in one- and two-family homes are never legal to rent as apartments because they usually lack more than one access point (more on that below) and are considered unsafe for use as living space. 

Certificate of Occupancy 

If you are want to confirm an apartment is legal, you should check the building's Certificate of Occupancy via the DOB’s Building Information System. It can easily be accessed on the DOB’s main page.

A Certificate of Occupancy will state whether or not the basement is considered habitable. It also ensures that the apartment meets legal requirements and building codes.

Are the ceilings high enough?

In order for the apartment to be legal, the ceiling height must be a minimum of 7.5 feet high. This is a change from the previous minimum of 8 feet, thanks to the recent revision of the city’s building codes.

Getting in and out

Basement apartments must have multiple means of egress in case one entrance is blocked by fire, for example.

There are important considerations for sleeping rooms in a basement apartment: They must have an egress window or door opening to the outside, the window sill can’t be more than three feet above the floor, and the window should be at least 30 inches tall by 24 inches wide.

If you can’t picture climbing out of the window in an emergency because it is too high or too narrow—it is unsafe and therefore unlikely to be legal.

Windows also bring in natural light and allow for ventilation, which are also DOB requirements for a legal dwelling. 

Other tell-tale signs 

If you have to access your apartment through a commercial space, like an office, that’s another indication the space is not likely legal.

Other warning signs that a basement apartment is not a legal dwelling: A lack of ventilation, as well as a bathroom and/or kitchen that isn’t fully functional—for example, when the place to cook is merely a hotplate on a table.

Extension cords plugged into outlets in another apartment are another warning sign. Pay attention and move on to the next place. 

File a complaint

If you find an online listing for an illegal basement apartment, you can help out your fellow New Yorker by flagging it. Most listings platforms give you the option to report a problem, which can trigger a review and possibly removal of the listing.  

You can also call 311 or go to 311 online to report an illegal basement rental, which can result in an inspection by HPD. It's a good idea to do this before the place is rented, because once a tenant is in place they will not have the ability to hold onto an illegal apartment.

—Earlier versions of this article contained reporting and writing by Austin Havens-Bowen


Jennifer White Karp

Managing Editor

Jennifer steers Brick Underground’s editorial coverage of New York City residential real estate and writes articles on market trends and strategies for buyers, sellers, and renters. Jennifer’s 15-year career in New York City real estate journalism includes stints as a writer and editor at The Real Deal and its spinoff publication, Luxury Listings NYC.

Brick Underground articles occasionally include the expertise of, or information about, advertising partners when relevant to the story. We will never promote an advertiser's product without making the relationship clear to our readers.