Building an ADU in New York State

New York has no statewide ADU law

New York does not have a state law that makes local governments allow ADUs. Each city, town and village decides through its own zoning code whether you can add a second unit, and on what terms.

State law gives a town board the power, "by local law or ordinance," to regulate and restrict the height, number of stories and size of buildings, the percentage of a lot that may be occupied, yards and other open spaces, population density, and the location and use of buildings and land. Those town rules apply only to the part of the town outside any incorporated village or city. Village Law section 7-700 gives a village board the same powers by local law, and says its rules "shall provide that a board of appeals may determine and vary their application." General City Law section 20 lets every city "regulate and limit the height, bulk and location of buildings" and divide the city into districts.

HCR's own ADU program reflects this. It says that "depending on the property and what the locality permits," ADUs may be detached units on single-family lots, basement apartments, garage conversions or other permitted units. To run the program, an administrator needs a letter of support from the town or city, which HCR says can show existing zoning that allows ADUs or a willingness to adopt ADU policies. [1][2][3][4][7]

ADU bills in the 2025-2026 legislative session

Several bills that mention ADUs were filed in the 2025-2026 session. As of October 10, 2026, the Senate and Assembly bill pages showed none of them had passed both houses:

• A6778 / S10217, the "accessory dwelling unit incentive act": would establish an ADU forgivable loan program run by HCR. A6778 was referred to the Assembly Housing Committee on March 14, 2025 and again on January 7, 2026. S10217 was referred to the Senate Housing, Construction and Community Development Committee on May 6, 2026.
• S5194 / A3446: would require each town, village and city to develop a "housing action plan for everyone." Both were last referred to their local government committees on January 7, 2026.
• S10503: would create a "build more, get more" incentive fund paying municipalities based on the number of new housing units they produce. It was amended and recommitted to the Senate Finance Committee on September 23, 2026.
• S10180A / A11427A: would allow a property tax exemption for dwelling units built for senior citizens or people receiving Social Security disability benefits. S10180A passed the Senate on June 2, 2026; A11427A was referred to the Assembly Rules Committee on June 4, 2026 and had not passed the Assembly.
• A7569: would create a property tax exemption for some homes in Suffolk County with ADUs rented to households in need, where the owner lives in the main building. It was last referred to committee on January 7, 2026.

None of these bills is law. If one passes, this page will be updated. [8][9][10][11][12][13][14][15]

State help: the Plus One ADU program

The 2022-2023 state capital budget set aside $85,000,000 to create and upgrade ADUs across New York, as part of a five-year housing plan. HCR's Plus One ADU program gives grants to local governments and nonprofit housing groups, which then run the program for homeowners in their area. It helps low- and middle-income homeowners who live in a single-family home to build a new ADU, or to bring an existing ADU up to local and state code.

You can't apply to the state directly. HCR says homeowners "must apply with the local program administrators (LPAs)." Its Plus One ADU page lists the participating places and who to contact in each. The list includes places such as Amherst, Brookhaven, the City of Buffalo, Cortlandt, Huntington, Islip, Ithaca, Kingston, Poughkeepsie, Troy, Utica, Woodstock, Yorktown and New York City. If your town isn't listed, HCR has an ADU program expansion interest form.

Under HCR's Round 4 request for applications (2026):

• Homeowner households can earn no more than 120% of area median income for the county or metro area.
• The most the program pays per unit is $125,000, or $175,000 in New York City, and that includes the administrator's delivery fee of up to 10%. HCR says that "in most or all cases, additional funds will be necessary to complete a project."
• Every ADU must be permitted by the municipality, and must be used as a primary residence of a tenant or family member.
• Homeowners sign a regulatory agreement of at least 10 years. Yearly certifications confirm the ADU is permanent housing, not a short-term rental.

Round 4 makes up to $12,000,000 available to local program administrators. Applications are accepted on a rolling basis, with priority for those received by September 3, 2026. New York City's version of the program is run by the city housing agency; see our New York City ADU guide. [4][7]

Building codes for ADUs

Outside New York City, an ADU is built under the New York State Uniform Fire Prevention and Building Code (the Uniform Code) and the State Energy Conservation Construction Code, which are in Title 19 of the state regulations. The Department of State says that "generally every city, town, village, and county administers and enforces building codes within its jurisdiction," so your building permit comes from your local code office.

The 2025 updates to the Uniform Code and Energy Code took effect December 31, 2025. The Department of State says the 2025 provisions that would ban fossil-fuel equipment and building systems in new buildings remain suspended by court order and "are neither effective nor enforceable" (update of July 2, 2026). On June 30, 2026 the federal Second Circuit Court of Appeals rejected the preemption challenge to those rules and affirmed the lower courts' judgments (Mulhern Gas Co. v. Mosley), so this may change; ask your code office which rules apply when you file. A local government that wants stricter construction standards must ask the state Code Council, and they take effect only if the Council approves them.

For cities of over one million people, state law says the existing building and fire prevention codes "shall continue in full force and effect" unless the Code Council finds them less stringent than the Uniform Code. New York City ADUs follow the NYC Construction Codes, which have a separate appendix for ADUs; see our New York City ADU guide. [16][17][18][19][20][21]

Property taxes on a new ADU

New York has a property tax exemption written for ADUs, but each government that taxes you decides whether to offer it. Real Property Tax Law section 421-p (the second section with that number, covering "the creation of accessory dwelling units") lets a county, city, town or village adopt it by local law after a public hearing, and a school district by resolution. Where it has been adopted:

• It covers work that creates one or more additional homes "on the same parcel as a pre-existing residential building," whether by building new or by remodeling. The law counts only residential buildings "designed and occupied exclusively for residential purposes by not more than two families."
• The added assessed value is exempt at 100% for five years, then at a shrinking share for five more years, after which the exemption ends. Only the first $200,000 of added market value counts.
• The work must start after the local law takes effect and be worth more than $3,000. You apply to your assessor on the state form by the taxable status date.
• A local law can reduce the percentage or limit which projects qualify.

Because your county, town or village and school district each decide separately, ask your assessor which of them have adopted it. A separate section, 421-f, lets local governments exempt part of the added value of improvements to existing one- and two-family homes. HCR's Plus One ADU program scores applicants in part on whether the community has committed to a 421-f exemption for the added value of an ADU, where applicable. See also our ADU property tax guide. [7][22][23]

New York City

New York City wrote ADUs into its zoning in the City of Yes for Housing Opportunity amendment, adopted by the City Council on December 5, 2024. It allows one "ancillary dwelling unit" of up to 800 sq ft per one- or two-family home, with limits in historic districts, some low-density districts and flood-risk areas. The owner must live on the lot when the ADU is first occupied. Permits come from the NYC Department of Buildings, which has accepted ADU filings in DOB NOW since September 30, 2025.

Our New York City ADU guide covers the size, height, setback and parking rules, basement and cellar units, permits and the city's programs. [5][6][24]

What to check with your town or village

Rules vary a lot from one municipality to the next, so ask your city, town or village planning or building department:

• Whether your zoning district allows an accessory apartment or ADU, and the minimum lot size.
• Whether it must be inside the house, or can be detached or over a garage.
• The maximum size, height and setbacks.
• Whether the owner must live on the property, and whether a special permit or board approval is needed.
• How many parking spaces you need.
• Building permit fees, and whether your county, town or village and school district offer the 421-p ADU property tax exemption.

Our ADU permit process guide, garage conversion guide, basement apartment guide and ADU cost guide cover the general steps. [1][2][3][22]

New York laws to know

• Town Law, Section 261

  Lets a town board, by local law or ordinance, regulate the height, stories and size of buildings, lot coverage, yards, density and the use of buildings and land, in the part of the town outside any village or city. Town ADU rules come from this zoning power. [1]

• Village Law, Section 7-700

  Gives a village board the same zoning powers by local law, and says the rules must let a board of appeals vary their application. [2]

• General City Law, Section 20 (24) and (25)

  Lets every city regulate the height, bulk and location of buildings, yards and density and divide the city into zoning districts. [3]

• Real Property Tax Law, Section 421-p (ADU exemption)

  Lets a county, city, town or village (by local law) or a school district (by resolution) exempt from property tax the added value of a new ADU built on the same lot as an existing home of one or two families. [22]

• Real Property Tax Law, Section 421-f

  Lets a county, city, town or village, after a public hearing, adopt a local law granting a property tax exemption for residential buildings that are reconstructed, altered or improved. [23]

• A6778 / S10217, Accessory Dwelling Unit Incentive Act (proposed, not law)

  Would create an ADU forgivable loan program run by HCR; both bills were still in their housing committees as of October 10, 2026. [8][9]

Questions people ask