What Is an ADU in NYC? A Beginner’s Guide to Accessory Dwelling Units
You’ve likely heard the buzz about ADUs (Accessory Dwelling Units). Maybe you’ve heard your neighbor discussing plans for a basement conversion, or your cousin in Brooklyn bragging about side rental income. Or perhaps you caught a glimpse of a sleek tiny cottage in someone’s backyard online and thought, “Wait… can I actually build one of those in New York City?”
What Exactly Is an ADU?
ADUs are quietly popping up all over NYC. Let’s dive into what they are, why they matter, and, most importantly, whether you can actually build one on your property. There are many types of ADUs. Here are some of the most common:
A finished basement apartment
A converted garage
A backyard cottage
An attic studio with a mini-kitchen
A “mother-in-law suite” above a detached garage
New Yorkers have been adding extra units to their homes for decades, but until recently, most of these weren’t legal. They existed in a gray area: unauthorized, and often unsafe. Today, ADUs have the benefit of new city and state regulations, rules, guidelines, and even incentives.
Why New York City Suddenly Cares About ADUs
New York’s housing situation can be unpredictable. Rent keeps rising, families are crowding together, older residents can’t stay in their homes, and younger New Yorkers are packing up and leaving. Legalizing ADUs could help change that.
The Benefits of an ADU
Create affordable housing
Help homeowners earn extra income
Support multigenerational living and housing for extended family
Reduce urban sprawl by using existing lots more efficiently
In 2023, New York State enacted the ADU Act, which mandates cities, including NYC, to permit ADUs in applicable residential zones as long as they comply with safety and zoning regulations.
Local ordinances are still being developed by the city, but the opportunity is officially here.
Can You Build an ADU in NYC?
Good question. In short, the answer is: yes, but it depends.
1. Varying Property Types
ADUs are allowed on lots with one- or two-family homes, meaning most rowhouses, brownstones, and detached houses in the outer boroughs (Queens, Staten Island, and parts of Brooklyn and the Bronx) are eligible. ADUs don’t apply to co-ops, condos, or buildings with more than two units.
2. Size & Location
An ADU cannot exceed a primary house in size. In many cases, it must be smaller than 800 square feet. If it’s detached (like a backyard cottage), it usually can’t take up more than 25–30% of your rear yard. It must meet light, ventilation, egress, and fire safety codes.
3. Permits
Lack of proper permits can lead to fines, eviction orders, and, most importantly, unsafe living conditions. The good news? NYC is working to simplify the approval process, and there may soon be grants or low-interest loans available to help cover conversion costs, especially for low- and moderate-income homeowners.
Takeaway — The Pros (and Cons) of Adding an ADU
The Upsides
Earn extra income: A well-designed ADU can bring in $1,500–$3,000 per month, depending on size and location - a real boost in a city where every dollar counts.
Flexible family living: Create space for aging parents, adult children, or caregivers - close enough to stay connected, but with privacy intact.
Increase property value: A legal, rentable unit makes your home more desirable and marketable if you ever decide to sell.
Support your community: Each ADU adds to NYC’s housing supply - one backyard cottage at a time.
The Challenges
Evolving regulations: NYC’s ADU regulations are still evolving. What’s approved today could change next year, so it’s important to stay informed as new rules roll out.
Landlord responsibilities: Renting out an ADU means managing leases, maintenance, and occasionally finding tenants.
The Bottom Line
Yes, building an ADU takes planning, but the payoff can be huge. You’re not just creating extra space, you’re unlocking new income, boosting your home’s value, and building something that supports your family and community for years to come.
With the city finally on board and new programs paving the way, there’s never been a better time to add an ADU in NYC.