Key New York ADU Laws
New York ADU Laws
- No statewide ADU law. ADUs are decided town by town, village by village, under municipal home rule (Town Law, Village Law, General City Law). The statewide bill S4547-A / A4854-A (2021-22) died in the Assembly Local Governments Committee; its last action was 5 January 2022.
- The word matters. Outside New York City the local terms are accessory apartment, mother-daughter and in-law apartment; search your town or village code for those.
- NYC is its own universe. City of Yes for Housing Opportunity (Zoning Resolution amendments adopted 5 December 2024) permits one ADU of up to 800 sq ft on 1- and 2-family lots citywide, with no parking, but bars backyard units in some low-density districts outside the Greater Transit Zone, in historic districts and in flood areas, and basement or cellar units in flood areas; the cellar-versus-basement distinction still decides most below-grade conversions.
- There is grant money. New York State HCR's Plus One ADU programme funds ADU construction through local administrators in participating municipalities; intake windows open and close (NYC's closed 12 June 2026).
What changed recently in New York
Gathered from the 3 cities below, with the bill or ordinance each one names. Statewide measures are listed once with the cities they reached, rather than repeated for each.
Statewide
- New York State: A6778/S10217, the 'ADU Incentive Act' (a forgivable-loan program, not a mandate), was re-referred to the Assembly Housing Committee on January 7, 2026; New York still has no statewide ADU law and ADUs remain a municipal home-rule matter — cited by Buffalo, Rochester
City by city
- Rochester: 2026-09-20 re-verification: the current Zoning Code (Chapter 120, eCode360 copy archived February 2026) still contains no ADU use; §120-163.A(1)(g) allows only a rear-yard guesthouse or servants' quarters with no kitchen and no rental. The old 35 ft height, 15/5/20 ft setbacks, 50-70 day timeline, $1,900-$3,300 fee and $400-$900 impact-fee figures were removed as unsourced; rents re-based on HUD FY2026 Fair Market Rents
- Buffalo: 2026-09-20 re-verification against UDO Chapter 496 (city PDF updated Sept 2023, unchanged in the Jan 2026 archive copy) and bufgreencode.com: ancillary dwellings are not permitted in the N-4-30 and N-4-50 Single-Family zones (Table 6A); height and setbacks corrected to the Sec. 3.2.3 carriage-house standards; the 50-70 day timeline, $2,000-$3,500 fee and $500-$1,000 impact-fee figures were removed as unsourced
- Rochester: Zoning Alignment Project: final draft Zoning Code, Zoning Map and FGEIS released April 20, 2026 (ADU cap raised from 400 to 800 sq ft; LDR changed from prohibited to special permit; new-build height cut from 24 ft to 15 ft). City Planning Commission informational meetings June 8 and 10, comment deadline June 18, recommendation vote July 13, 2026. City Council adoption still pending as of September 20, 2026
- New York City: December 5, 2024: City of Yes for Housing Opportunity adopted: 'ancillary dwelling unit' defined in ZR 12-10 (800 sq ft, one per one- or two-family home, owner primary residence at initial occupancy), backyard ADU height, rear-yard and 5 ft lot-line rules in ZR 23-341, 10 ft building separation in ZR 23-371, 0 percent parking in ZR 25-222 and 25-232
- New York City: April 9, 2026: DOB began accepting filings for a new one-family house built with a cellar ADU under 1 RCNY 105-08(d)(4) and Local Law 80 of 2026; the Local Law 126 basement and cellar legalization pilot is still not taking applications until DOB promulgates its rule (DOB ADU page, revised 04/09/26)
- Rochester: New York State's Plus One ADU grant program funds units only through local administrators in participating municipalities; check NYS Homes and Community Renewal's program page for a Rochester-area administrator before counting on it
- New York City: June 12, 2026: HPD closed intake for the Plus One ADU Program (up to a $220,000 HPD loan plus a $175,000 HCR grant per the program term sheet, so up to $395,000 combined); a mailing list is open for the next round
- Buffalo: BURA Plus One ADU Program (with NYS Homes and Community Renewal): up to 100% construction or rehab funding for owner-occupied single-family homes under 120% of AMI; applications were closed as of September 2026
- Buffalo: The Buffalo Green Code (UDO Sec. 6.1.2.B) imposes no owner-occupancy requirement on ancillary dwellings, and Sec. 8.3.1.A sets no minimum off-street parking anywhere in the city (in force since January 2017)
- New York City: Pre-Approved ADU Plan Library: 8 DOB- and FDNY-reviewed backyard designs listed by DOB's Office of Technical Certification and Research as of September 2026
- New York City: September 30, 2025: ADU filings opened in DOB NOW: Build; Local Laws 126 and 127 of 2024 (Building Code Appendix U) took effect June 16, 2025
- New York City: New York State has no statewide ADU mandate; NYC's rules come from the Zoning Resolution and Local Laws 126 and 127 of 2024
What the rules actually look like across New York
Statewide law sets a floor; the numbers that decide your project are local. Here is the spread across the 3 New York cities covered here, taken from each city's own ordinance rather than a state summary.
| Question | Across New York |
|---|
| Are ADUs permitted? | 2 of 3 permit them, 1 have an ordinance in progress. |
| Detached size cap | Median 800 sq ft, from 500 to 1,000 sq ft across the 3 cities publishing a numeric cap. |
| Owner-occupancy | Required in none of them. |
| Build cost | $105,000 to $450,000 depending on city and unit type. |
| Easiest and hardest here | Buffalo scores 6/10; Rochester scores 2/10. |
Recomputed whenever a city page changes, so this and the city pages below cannot disagree.
New York Cities ADU Comparison
| City | Max Size | Setbacks | Permit Fees | Build Cost | 1BR Rent | Score |
| Buffalo |
1,000 sq ft gross floor area max; a detached ancillary dwelling must also be lower in height (feet) and smaller in footprint than the principal building, and must meet the Sec. 3.2.3 carriage-house standards (UDO Sec. 6.1.2.B). |
0 ft base for an ancillary carriage house; if it encroaches on the main house's required rear yard it must be at least 18 in from the lot line (no setback along an alley) and all accessory structures together may not cover more than 50% of that yard (UDO Sec. 3.2.3.D). |
Building-permit fees are set on construction value; the current schedule was not retrievable online - confirm with Permit & Inspection Services. Zoning fees (OSP memo eff. July 1, 2025): area variance $150 (1-2 units), minor site plan $350, special use permit $350. |
$110,000-$220,000 |
$1,000-$1,300/mo |
6/10 |
| New York City |
800 sq ft of zoning floor area (ZR 12-10), which counts toward the lot's floor area ratio; a backyard ADU may also cover no more than one-third of the required rear yard (ZR 23-341(b)(4)), so a 500 sq ft footprint needs a 1,500 sq ft rear yard. Converting a garage or shed that existed before Dec 5, 2024 is not a 'backyard ADU' and is allowed even where new ones are barred. |
A free-standing backyard ADU may stand inside the required rear yard as a permitted obstruction but must be at least 5 ft from the rear lot line and cover no more than one-third of the rear yard (ZR 23-341(b)(4)). A converted pre-Dec 2024 garage may keep its existing non-complying position (DOB ADU Types page). |
DOB filing fee (Admin. Code 28-112.1): a detached ADU filed as a New Building pays $0.06 per sq ft with a $100 minimum, so $100 for 800 sq ft; an interior conversion filed as an Alt-CO pays $170 for the first $5,000 of work plus $2.60 per $1,000 above that (about $550 on a $150,000 job). |
$150,000-$450,000 |
$2,500-$3,400/mo |
5/10 |
| Rochester |
Not applicable today. Proposed (ZAP final draft Sec. 3.7.A.7): 800 sq ft maximum, not exceeding the gross floor area of the main house; one bedroom at most (3.7.A.6); a detached unit must sit in the rear yard (3.7.A.5) and district lot-coverage limits still apply. |
Not applicable today. Proposed: the draft sets no zoning setback for ADUs - 'all setbacks for the ADU shall be governed by the NYS Building and Uniform Fire Prevention Code' (Sec. 3.7.A.9); a detached ADU must be in the rear yard (3.7.A.5). |
Building-permit fees: the schedule was not retrievable (cityofrochester.gov is bot-walled) - confirm with the Bureau of Zoning and Permitting. Zoning fees in §120-206.1 (as amended 2010): special permit $250, use/area variance $250, certificate of zoning compliance $50. |
$105,000-$210,000 |
$1,000-$1,300/mo |
2/10 |
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