ADU laws in New York

In plain words

New York does not have a statewide law that makes towns allow accessory dwelling units. An accessory dwelling unit, or ADU, is a small second home on the same lot as a house. It can be inside the house, attached to it, or in the backyard. In New York, each city, town and village writes its own zoning rules. Zoning is the local law that says what you can build and where. So the answer depends on exactly where your property sits. A village can even have different rules from the town around it.

Many places near Rochester and the Finger Lakes now allow ADUs, but the details vary a lot. Some allow only an apartment inside or attached to the house. Others allow a detached backyard cottage. Many require owner occupancy, which means the owner must live in the main house or the ADU. Many also cap the size and limit bedrooms. Some want an extra parking space or a special permit, which means a public hearing before a local board.

The state helps in two ways. Since 2024, a local government can choose to offer a ten-year property tax break on the value an ADU adds. It only applies where your city, town, village, county or school district has adopted it. The Plus One ADU program also offers grants of up to $125,000 outside New York City. It is for homeowners earning up to 120% of the area median income. That is the middle household income for your region. You apply through a local partner, and right now none serves Monroe or Ontario County.

New York City allowed ADUs in December 2024. They are limited to owner-occupied one- and two-family homes, with limits in flood zones.

Town-by-town rules near Rochester

New York leaves ADU rules to each town, village and city, so the local code is the answer that counts. We’ve checked every municipality in Monroe and Ontario counties (some only by searching the online code) and the ones in Wayne, Livingston and Yates whose codes are online.

Nearby: Genesee County · Seneca County

Town has no ADU rules? Read what to do when your town hasn’t written ADU rules, with a letter you can send. Or check your property to see your town’s rules right away.

The rules at a glance

What to do next

1. Confirm which government controls your parcel (a village or the surrounding town) and its zoning district. Your tax bill or the county parcel map shows this; then call that municipality's building or code enforcement office.
2. Read that municipality's ADU section (many are on ecode360.com) and ask whether an ADU is a permitted use, needs a special use permit, or needs site plan review, plus the size, bedroom, owner-occupancy, parking and setback limits (a setback is the required distance from your property lines).
3. If you are on a septic system or well, ask the office that reviews septic systems what an extra dwelling requires before you design anything, since septic sizing depends on bedroom count. In many counties that is the county health department. In Ontario, Wayne and Yates counties it is the NYS Department of Health’s Geneva District Office.
4. Ask your assessor whether your town, county and school district have adopted the RPTL 421-p ADU tax exemption, and if so file Form RP-421-p-adu before the taxable status date.
5. If your household income may be at or below 120% of the area median, check the Plus One ADU page at hcr.ny.gov/adu for a local administrator that serves your town.
6. Get written confirmation that your specific plan is allowed, if local rules and the property allow it, before signing a nonrefundable contract with any builder.

Grants, loans and tax breaks

• Plus One ADU Program (NYS Homes and Community Renewal): Grants funded by $85 million from the 2022-23 state capital budget. A homeowner can receive up to $125,000 per ADU outside New York City or $175,000 inside it; that amount includes the local administrator's fee (up to 10%), design and construction, and most projects need other money too. Homeowners must live in the house and have household income at or below 120% of the area median. The ADU must be legal under local zoning and used as a primary home for a tenant or family member, not a short-term rental, under a regulatory agreement of at least ten years with yearly certifications and site visits every two years. Homeowners apply through a Local Program Administrator; as of October 3, 2026, HCR's list has none serving Monroe, Ontario or the other Rochester-area counties. The nearest administrators serve their own areas only: Buffalo (Buffalo Urban Renewal Agency), the Town of Amherst, Ithaca (Ithaca Neighborhood Housing Services) and Utica. Round 4 (up to $12 million, up to $3 million per administrator, priority deadline September 3, 2026, rolling after that until the money is committed) is open to towns and nonprofits that want to become administrators. Program page
• Plus One ADU Gap Loan Program: HCR issued a request for lenders on January 5, 2026, offering up to $3 million to community development lenders (CDFIs) and state-supervised nonprofit lenders; proposals were due February 6, 2026. Under its terms, homeowners already accepted into Plus One could borrow $10,000 to $85,000 at 0% interest, repaid over up to 30 years, to cover a documented funding gap after all other money is lined up. Only for municipalities that take part in Plus One. Which lender was chosen, and whether loans are being made yet, was not confirmed. Program page
• Local-option ADU property tax exemption (RPTL §421-p, Form RP-421-p-adu): Where a city, town, village, county or eligible school district has adopted it, the added assessed value from a new ADU on a one- or two-family property is fully exempt for five years, then 75%, 50%, 25%, 15% and 5% in years six to ten, capped at $200,000 of added market value. The work must start after the local law is adopted and be worth more than $3,000. A locality may adopt smaller percentages or limit the types of work that qualify. File Form RP-421-p-adu with your local assessor before the taxable status date. The exemption ends if the property is sold (other than to heirs) or stops being used as housing. Program page
• NYC Plus One ADU (HPD) and pre-approved plans: New York City only. In March 2026 the city reopened Plus One ADU with up to $395,000 in combined city and state financing for qualified homeowners (interest applications ran through June 12, 2026) and launched a library of nine pre-reviewed backyard cottage designs. Program page

What your town still decides

New York is a home-rule state for land use. Every city, town and village writes its own zoning code, and a village can have different rules from the town around it. No state statute requires towns to allow ADUs, approve them administratively, or limit owner-occupancy, size, parking or setback rules. In practice local codes range from no ADU section at all, to internal-only units, to attached or detached units that need a special use permit (with a public hearing) or site plan review, to ADUs listed as a permitted use. Many upstate codes require the owner to live on site, cap bedrooms, require an extra parking space and bar selling the ADU separately. ADUs that need a county referral (for example near county roads or farmland) may also go to the county planning board under General Municipal Law 239. The state's main levers are money and incentives rather than rules: the Plus One ADU grant and gap-loan programs, the 2024 local-option tax exemption, and the Pro-Housing Communities program, whose certification a municipality must hold before it can apply to several discretionary state funding programs (such as the Downtown Revitalization Initiative and NY Forward) but which does not require ADUs. Governor Hochul did propose a statewide rule in January 2022 (every owner-occupied residential lot would get at least one ADU), but she dropped it from her budget in February 2022 after suburban opposition. The FY2026 (May 2025) and FY2027 (May 2026, 'Let Them Build' SEQRA reforms) state budgets did not add any ADU zoning mandate. Every live 2025-2026 ADU bill is an incentive, tax or grant bill; none would require towns to allow ADUs.

Examples of local rules

• New York City: City of Yes for Housing Opportunity (approved by the City Council on December 5, 2024) allows one ADU per one- or two-family building, up to 800 sq ft, in all residential districts. The owner must live on the property. No parking is required. Backyard and basement ADUs are not allowed in coastal and inland flood zones, and backyard ADUs are not allowed in historic districts, in R1-2A/R2A/R3A districts outside the Greater Transit Zone, or in the Bay Ridge special district west of Ridge Boulevard. In March 2026 the city added a pre-approved plan library of nine backyard cottage designs and reopened its Plus One ADU program. A state court on Staten Island dismissed a lawsuit against City of Yes in November 2025; the challengers said they would appeal. Source
• City of Rochester (Monroe County): Rochester is rewriting its 2003 zoning code through the Zoning Alignment Project. The April 2026 Final Draft (section 3.7.A) would allow one ADU per lot with a single-family detached house, attached or detached (detached only in the rear yard), up to 800 sq ft and no bigger than the main house, one bedroom, and no taller than 15 feet or the house, whichever is less. An attached ADU must share at least 25% of its wall area (or its floor or ceiling) with the house and cannot extend past the front of the house. The ADU cannot be sold separately, cannot have its own driveway, and shipping containers are not allowed. The use table lists ADUs as permitted in most districts and by special permit in one; a detached ADU needs Level A site plan review. The draft's ADU section has no owner-occupancy rule. It is NOT law yet: as of late September 2026 the city planned public hearings on October 21-22, 2026 and a City Council vote as soon as November 2026. Source
• Town of Clarkson (Monroe County): One ADU per home, with a special use permit from the Planning Board after a public hearing. One bedroom, no bigger than 30% of the main home's living space. Inside the house only in the RS-10 district; in AR and RS-20 it can be a detached building behind the house. It needs room for one more car in the existing driveway and isn't allowed on a lot that doesn't meet current zoning rules. The owner must live on site and sign a notarized statement, and the ADU can't be sold separately. Source
• Village of Fairport (Monroe County): The use table in section 551-23 lists ADUs as a permitted use in the RLD, RN and RTN residential districts, and section 551-26(A) sets the standards: one per lot with a single-family home. The ADU must be inside the house or attached to it, sharing at least 25% of its wall area or its floor or ceiling with the house. Detached ADUs, new or existing, are prohibited. Maximum one bedroom and 650 sq ft, and an addition cannot extend past the front of the existing house. No owner-occupancy rule appears in the ADU section. Source
• Village of Pittsford (Monroe County): Code section 210-24.3 allows one ADU per single-family home with a special use permit. An ADU inside the house is only allowed if the house has at least 2,500 sq ft of living space and the ADU has one entrance on the side or rear. An ADU in a detached garage or accessory building must be in the rear yard and that building must have at least 500 sq ft of living space. Not allowed on nonconforming lots. Maximum two bedrooms, one extra off-street parking space in the existing driveway, owner must live on site (notarized affidavit; the permit can be revoked if not), and the ADU cannot be sold or subdivided off. Source
• Town of Canandaigua (Ontario County): Chapter 220 lists 'one single-family dwelling and one attached or detached accessory dwelling unit per lot' as a permitted use in the AR-1, R-1-30, SCR-1 and Residential Lake (RLD) districts. In the Scenic Viewshed Overlay, an accessory apartment is allowed only where public sewer and water exist. Other sections of the code (site plan, setbacks, lake rules) still apply. Source

What we’re still confirming

• Two state bills that would put state money toward ADUs are still in committee and expire December 31, 2026 if they don't pass; neither would make towns allow ADUs.
• We found no list of which towns, counties and school districts near Rochester have adopted the state's ADU property tax exemption; ask your assessor.

Laws, bills and citations

This is general information, not legal advice. Your town, village, city or county decides what can be built on your property. If something here looks out of date, email the team.