Everything homeowners ask about building an ADU in Buffalo — answered with 2026 data.
Yes, ADUs are allowed in By right ('Dwelling, Ancillary', UDO Table 6A) in N-1D, N-1C, N-1S, N-2C, N-2E, N-2R, N-3C, N-3E, N-3R and the D-R, D-M, D-E, D-S and D-C district zones. Not permitted in the N-4-30 and N-4-50 Single-Family zones or in industrial, open-space and rail-corridor zones. A detached unit uses the carriage-house building type, allowed in N-1C, N-2C, N-2E, N-2R, N-3C, N-3E and N-3R (Table 3A). in Buffalo, NY. The maximum size for a detached ADU is 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). Attached ADUs can be up to 1,000 sq ft gross floor area - the same cap applies to attached and interior units. Buffalo has an ADU-friendliness score of 6/10. Check our full Buffalo ADU rules page for complete zoning details.
ADU construction in Buffalo typically costs $110,000-$220,000. The cost per square foot averages $120-$250. Garage conversions are more affordable at $55,000-$130,000, while prefab ADUs cost $80,000-$180,000. Permit fees add 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. to your budget. See our detailed Buffalo ADU cost guide.
Detached ADUs in Buffalo can be up to 1,000 sq ft gross floor area max; a detached ancillary dwelling must also be lower in height. Attached ADUs are limited to 1,000 sq ft gross floor area - the same cap applies to attached and interior units. Junior ADUs (JADUs) have a cap of No JADU category in Buffalo or New York; a basement, attic or in-law unit is simply an ancillary dwelling under the same 1,000 sq ft cap. Maximum height is Carriage house: 2 stories max in N-2C, N-2E, N-2R, N-3C, N-3E and N-3R (3 stories in N-1C), and always lower in feet than the main house. Where the site abuts a side or rear lot line in an N-2R, N-3R, N-4-30 or N-4-50 zone: 18 ft max along the required setback line, up to 24 ft with 1 ft of extra setback for each foot above 18 ft (UDO Sec. 3.2.3.E). You are allowed up to The UDO sets no numeric cap; Sec. 6.1.2.B defines an ancillary dwelling as 'a dwelling unit' incidental to the principal dwelling - plan on one, and confirm with the Zoning Administrator before designing a second. on a qualifying lot.
Rear setback: 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). Side setback: 0 ft base (interior and corner side); the same 18-in-from-lot-line and 50%-of-required-yard rule applies when the unit sits in a required side yard (UDO Sec. 3.2.3.D). Above 18 ft, a 1:1 step-back applies next to N-2R, N-3R, N-4-30 or N-4-50 lots (Sec. 3.2.3.E). Front setback: At least 10 ft behind the principal structure ('Front yard (min): 10 ft from principal structure', UDO Sec. 3.2.3.D); a carriage house may not sit forward of the main house. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None - the UDO sets no minimum off-street parking for any development (Sec. 8.3.1.A); Buffalo removed parking minimums citywide when the Green Code took effect in January 2017. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required by the UDO - Sec. 6.1.2.B has no owner-occupancy or rental restriction. (BURA's Plus One ADU funding program does require owner-occupancy for grant recipients.). Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Buffalo is typically Not published - the city does not post plan-review times for residential permits; ask Permit & Inspection Services when you register the project. Plan check: Not published; part of the building-permit review by Permit & Inspection Services. Pre-approved plans availability: None - Buffalo publishes no pre-approved ADU plan set (Sept 2026).
Average ADU rental income in Buffalo: 1-bedroom units rent for $1,000-$1,300/month, 2-bedroom units for $1,150-$1,550/month. Short-term rentals: Not addressed by the ADU rules; confirm with Permit & Inspection Services. Expected ROI: Not estimated; HUD FY2026 SAFMR $970-$1,290/mo (1-BR) against a $110,000-$220,000 build.
The minimum lot size for an ADU in Buffalo is No ADU-specific minimum. An ancillary carriage house uses the lot-area, lot-width and coverage limits of the principal building (Sec. 3.2.3.C); e.g. a detached house needs 1,500 sq ft in N-2R and 1,800 sq ft in N-3R, with 70% max building coverage (Sec. 3.2.6). This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Buffalo, a garage conversion typically costs $55,000-$130,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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