Can New York Unlock ADUs? – The Legal Landscape for Accessory Dwellings in NY State and NYC
This post examines current ADU regulations (and prohibitions) in New York State and New York City, recent legislative proposals, and pilot programs aimed at bringing ADUs into the light.
In New York, accessory dwelling units have long existed in the shadows – think basement apartments or garage studios rented informally. But legal ADUs are rare due to strict zoning. Now, pressure is building to change that. This post examines current ADU regulations (and prohibitions) in New York State and New York City, recent legislative proposals, and pilot programs aimed at bringing ADUs into the light.
A History of Restriction
Unlike California, New York has no statewide law guaranteeing the right to build an ADU. In fact, in New York City – home to over 8 million people – ADUs (in the form of backyard cottages or standalone structures) are generally not allowed under zoning. Many suburban communities across New York State similarly ban or severely limit ADUs in single-family zones. The result is a dearth of legal ADUs, even as the state faces housing shortages in many areas.
Basement and cellar apartments in NYC are the closest equivalent to ADUs, but the vast majority are illegal under current building codes. New York City’s housing stock includes tens of thousands of these informal units, often occupied by low-income families, but bringing them up to code is expensive and complicated.
On Long Island and in other suburbs, local zoning has traditionally required single-family homes on large lots with no provision for second units. For example, the Village of Tarrytown in Westchester County only recently amended its code in 2023 to permit detached ADUs on lots of 15,000 sq. ft. or larger – and even that is in carefully defined circumstances. Many towns still prohibit a second dwelling on a single-family lot entirely.
This restrictive landscape persisted until very recently. However, the housing affordability crisis in the New York metropolitan area has prompted lawmakers and officials to reconsider ADUs as a potential solution for gentle infill housing.
A Push for Statewide Change – Hochul’s Attempt
Recognizing that local zoning was a major barrier, New York Governor Kathy Hochul in early 2022 proposed statewide ADU legislation. Her plan would have required local governments across New York to allow at least one ADU on owner-occupied residential lots. It was part of Hochul’s agenda to boost housing supply and was included in her 2022–23 budget proposal.
The backlash from some suburban lawmakers was swift. Concerns about local control and neighborhood character led to fierce opposition, particularly from parts of Long Island and the northern suburbs. Ultimately, Gov. Hochul pulled the ADU proposal from the budget in March 2022 amid the controversy. The failure of this attempt illustrated the political challenges of overriding local zoning in New York.
However, the conversation didn’t end there. Even though the statewide mandate was shelved, it put ADUs on the policy map. The mere fact that the Governor had pushed for it signaled that New York might eventually follow in California’s footsteps, albeit on its own timeline.
In 2023, state legislators introduced new bills focused on ADUs. For instance, NY Senate Bill S9090 (2022) proposed financial incentives for ADU construction as a more carrot-than-stick approach. There’s also discussion of revisiting statewide legalization in the context of a broader housing package.
As of early 2025, no New York State law explicitly legalizes ADUs everywhere – meaning we still rely on local governments to open the door.
New York City – Slow Steps Toward ADUs
New York City’s zoning doesn’t currently have a straightforward allowance for ADUs on most properties. The city’s focus has been on two areas: legalizing existing basement units and exploring detached ADUs through limited pilots.
Basement Apartment Conversions: In 2019, NYC launched a Basement Apartment Conversion Pilot Program in East New York, Brooklyn. The idea was to help a handful of homeowners bring illegal basement units up to code, testing what reforms might be needed. The pilot ran into challenges – high costs and stringent code requirements – and only a few conversions were completed. An interim report by the nonprofit CHPC noted issues like low ceilings and flood plain rules that made many basements ineligible. The pilot “graduated” just 5 participants, highlighting how tough it was to legalize these units under existing rules.
Learning from that, the city and state pivoted to a more ambitious effort: the “Plus One ADU” program. Launched in late 2023, the Plus One ADU pilot aims to help NYC homeowners create a variety of accessory units – not just basements, but also garage conversions or backyard cottages – with substantial financial backing. The program provides up to $395,000 in funding per project (combining city and state grants/loans) to cover design and construction of an ADU. It specifically targets low- and middle-income homeowners and encourages units that could house elderly family members, returning college grads, or provide rental income for the owner.
Mayor Eric Adams has framed this as part of his “City of Yes” housing plan, describing ADUs as a way to “build a little more housing in every neighborhood” without drastically changing the look of communities. The Plus One ADU pilot is essentially a test run: by funding a small number of ADUs across the five boroughs, the city can gauge interest and identify regulatory barriers to address in the future. The program opened for applications in late 2023 and will run through early 2024 (initial application deadline was February 2024).
What’s allowed in NYC currently? For detached ADUs (backyard cottages), current zoning is generally prohibitive except in certain low-density zones that permit accessory structures of limited types. In practice, almost all new ADUs in NYC require either a waiver, a zoning change, or are being done under the special pilot program. However, NYC is actively studying changes to zoning and codes. The Adams administration’s City of Yes proposals include an initiative to legalize ADUs more broadly. They’ve indicated interest in enabling homeowners to build smaller second units, particularly to help multi-generational families. Any concrete zoning amendment will require City Council approval, likely a heavy political lift similar to the state battle.
Notably, in the final 2022-23 state budget, even though the broad ADU legalization was removed, a provision was included to make it easier for NYC to legalize existing basement units. This signaled continued support for incremental progress, at least for one type of ADU.
Suburban and Upstate New York – Patchwork Progress
Outside NYC, a few local governments have begun to allow ADUs, marking a slow shift:
Westchester County: As mentioned, places like Tarrytown and the Town of Greenburgh adopted ADU ordinances in 2023. Greenburgh’s new law (Local Law 2-2023) permits one ADU per single-family lot under certain conditions. The fact that these affluent suburbs are cautiously opening the door is significant; they often set an example for neighbors.
Long Island: Long Island has been particularly resistant, with very few jurisdictions allowing ADUs. Some advocates point out that legalizing ADUs could provide housing for local workers and adult children, but local opposition remains strong. As of now, most of Nassau and Suffolk counties prohibit detached ADUs. However, both counties have programs encouraging homeowners to rent spare bedrooms to students or seniors (which is different from creating an independent ADU).
Upstate New York: In smaller cities and towns upstate, ADU rules vary. A number of municipalities allow “accessory apartments” within a home (like an upstairs unit or basement) but not a separate cottage. College towns or areas with tourist housing sometimes permit carriage houses or garage apartments on large lots. Overall, though, ADUs are not common or well-known upstate, and many zoning codes are silent on them – meaning they’re effectively not permitted unless by variance.
State Incentives: New York State is trying to spur local action via funding. The $85 million Plus One ADU state program (administered by NY Homes and Community Renewal) provides grants to municipalities or non-profits to develop local ADU programs. Essentially, the state will bankroll pilot ADUs in places that volunteer. The program focuses on low- or middle-income owner-occupants and aims to create “safe, quality ADUs” by covering design, permitting, and construction oversight through partner organizations. Communities have to apply, and by late 2023, the state was reviewing proposals. This is a big carrot: towns that might not have staff or money to deal with ADUs can get state funds to hire experts, subsidize homeowners, and craft local rules that ensure safety and neighborhood fit.
It’s an interesting approach – rather than forcing every locality to allow ADUs, New York is offering cash to those willing to experiment. The hope is that successful pilots in some towns will ease fears and create models that others can copy.
Key Legal Points for Would-be ADU Builders in NY
For a New York homeowner curious about ADUs, the first question is: what do your local codes say? Because New York has no uniform ADU law, rules differ city by city, town by town. Here are some general considerations:
Owner-Occupancy: In places that do allow accessory units (like an in-law apartment), they almost always require the primary homeowner to occupy either the main house or the ADU. For instance, a draft ADU bill in the NY Assembly (A1401, 2023) would have required owner-occupancy if it had passed. Expect this requirement unless laws change; it’s seen as a way to prevent absentee landlords and maintain the character of single-family areas.
Unit Size Limits: Typically, ADUs (where allowed) have strict size caps relative to the main house. A common rule is max 30–40% of the primary dwelling’s square footage or an absolute cap (often 600–800 sq. ft.). For example, Croton-on-Hudson’s ADU ordinance sets the max at 800 sq. ft. or 40% of the main house’s size, whichever is less. These rules ensure ADUs remain “accessory” in scale.
Lot Requirements: Suburban codes often stipulate a minimum lot size or width to site an ADU. As noted, Tarrytown only allows detached ADUs on lots 15,000 sq. ft. or larger, which excludes smaller properties. Setback requirements (distance from property lines) can also effectively constrain where an ADU could go – e.g., needing 10+ feet from side and rear boundaries.
Parking: Many NY localities, if they consider ADUs, will require off-street parking for them (usually one space per ADU). This can be a hurdle if a driveway is small. Some more progressive approaches might waive extra parking if street parking is available or if the ADU is near public transit, but such leniency is not common yet in NY as it is in California.
Building Code: New York’s building codes for a new dwelling unit are stringent. A detached ADU must meet the same code as a new small house – which means compliance with energy code, insulation, heating, egress, fire safety, etc. Basement units must have minimum ceiling heights (usually 7 feet), proper means of egress (like an emergency escape window or door), and adequate light/ventilation. This is often where illegal units fall short. The city or state have not created separate “ADU building codes,” so full compliance is required, which can be costly for conversions.
Short-Term Rentals: If you do somehow establish a legal ADU, be aware that some jurisdictions might restrict using it for short-term rentals (Airbnb-type use). New York City already has strict regulations on short-term rentals in general, and upstate towns sometimes ban short-term rentals in residential zones. So an ADU may need to be a long-term rental (30 days or more) unless local laws say otherwise.
In New York City specifically, a homeowner currently has very limited legal pathways to create an ADU outside of the pilot program. They might convert part of their home to a separate unit if zoning allows a two-family use on their lot. For instance, a homeowner in a zoning district that permits two-family homes could split their house into an owner unit and a rental unit (this is more a duplex scenario than a backyard ADU). But if the zoning is strictly for single-family, that’s not allowed without a variance.
The Road Ahead in New York
New York’s journey to ADU legalization is nascent but picking up steam. There are signs that 2024–2025 could bring meaningful change:
Governor Hochul has made housing a priority. In her 2023 State of the State, she announced a goal of 800,000 new homes in the next decade across New York. ADUs could be one slice of that, especially since upzoning for larger projects faces pushback. Expect the ADU concept to resurface in Albany’s legislative discussions, potentially with a more modest approach or incentive-driven plan to appease suburbs.
New York City will likely propose zoning changes as part of the City of Yes initiative. Deputy Mayor Maria Torres-Springer explicitly said they are “getting rid of outdated rules that stop homeowners from updating their homes to meet their needs”, referencing ADUs. This could mean allowing owner-occupants to add an internal or detached accessory unit more broadly. Any such proposal will undergo public review (ULURP process) and could be contentious, but the city’s housing pressures are immense – giving reform a real shot.
Success stories from the pilot programs could pave the way. If the Plus One ADU pilot manages to produce, say, a dozen high-quality ADUs and demonstrates that they can be built safely and fit into neighborhoods, it provides a proof of concept. Lawmakers can point to those examples to alleviate fears (“See, a small cottage in a Queens backyard didn’t destroy the neighborhood, and it provided a home for a grandmother on a fixed income”).
Community perspectives are gradually shifting. Even some earlier opponents in suburbs are acknowledging the need for housing solutions. A group of Long Island officials convened in 2022 to discuss ADUs and basement units after tragic incidents where illegal units had unsafe conditions. There’s a growing recognition that it’s better to proactively create a legal framework with safety standards than ignore the underground reality.
In summary, New York is at the beginning of what could be a significant transformation in single-family zoning norms. Right now, the legalities remain challenging – ADUs are mostly not allowed outright – but the momentum for change is building. Landlords and homeowners interested in ADUs should keep a close watch on state and local proposals in the coming year. It’s quite possible that by the end of 2025, New York will enact new policies making ADUs easier to build, following the path of states like California and (as we’ll see next) Massachusetts.
For now, anyone in New York considering an ADU should: research if their locality has any ADU pilot or provision (a few do), perhaps engage with local officials about the Plus One program opportunities, and ensure any existing informal unit is made safe even if not yet fully legal. New York’s housing future may well include ADUs as a key ingredient – unlocking tens of thousands of new homes in basements, attics, and backyards, once the legal barriers come down.