ADU · Monroe County
Can you build an ADU in Mendon, NY?
Town of Mendon has 4 districts. 3 districts prohibit ADUs, 1 requires a special-use permit. Check your address to confirm the district that applies to your parcel:
What the Mendon code indicates by district
The table below shows how each district treats ADUs, alongside the lot and setback standards that govern a second unit. District boundaries and conditions vary, so treat this as a starting point and confirm the district that applies to your parcel.
| District | Min lot | Setbacks F / S / R | Max height | ADU |
|---|---|---|---|---|
| Residential Agricultural 5 (RA-5) — the town's largest-lot district, stated as a DENSITY of 1 LOT PER 5 ACRES rather than as a flat minimum lot area, which is how every Mendon residential district is written. Front setback 60 ft on town and county roads, RISING TO 80 FT ON A STATE ROAD; side 20 ft; rear 20 ft; height 2 1/2 stories or 35 feet. THE LOT WIDTH IS TWO SEPARATE NUMBERS AND THE GAP IS THE LARGEST IN THE TOWN: 100 ft of width AT THE RIGHT-OF-WAY but 300 FT AT THE BUILDING LINE. The recorded 300 is the building-line figure because that is what governs where a house can actually sit; the 100 ft ROW figure is a frontage minimum and is far smaller, which means RA-5 expressly contemplates a lot that necks down to the road and opens out behind — a flag-lot geometry. Sizing a subdivision from the ROW width alone would badly overstate how many lots a road frontage can carry. MENDON STATES NO LOT COVERAGE IN ANY RA DISTRICT AND maxLotCoverage IS NULL BY DESIGN — the schedule's third column is headed 'Habitable Floor Area (square feet) or Lot Coverage' and for RA-5 it carries only floor area: a MINIMUM of 1,200 sf for a one-storey dwelling and 1,500 sf for anything else. That is a house-size FLOOR, the opposite of a coverage ceiling, and the two must not be confused because they share a column. RA-5 is one of only two districts permitting TOURIST HOMES AND BED-AND-BREAKFAST ESTABLISHMENTS by special use permit; it has no residential-conversion route and no multi-unit route. | 5 ac | 60 / 20 / 20 ft | 35 ft | No |
| Residential Agricultural 2 (RA-2) — a density of 1 LOT PER 2 ACRES, not a flat lot minimum. Lot width is 50 ft at the right-of-way and 200 FT AT THE BUILDING LINE; the recorded figure is the building-line width, and note the ROW frontage drops to just 50 ft here against RA-5's 100 ft, so the flag-lot geometry is even more pronounced — a two-acre RA-2 lot may present only 50 feet to the road. Front setback 60 ft on town and county roads and 80 ft on a state road; side 20 ft; rear 20 ft; height 2 1/2 stories or 35 feet. Setbacks are identical to RA-5 and RA-1 — the three agricultural districts differ ONLY in density and in building-line width, not in envelope. NO LOT COVERAGE IS STATED, so maxLotCoverage is null by design; the schedule gives only a MINIMUM habitable floor area of 1,200 sf for a one-storey dwelling and 1,500 sf for anything else, which is a house-size floor rather than a coverage cap. RA-2 IS ONE OF THE TWO MOST RESTRICTED DISTRICTS IN MENDON FOR ANYTHING BEYOND A SINGLE HOUSE: unlike RA-5 it does not permit tourist homes or bed-and-breakfasts, and unlike RS-30 it has no residential-conversion or multi-unit route. One dwelling per lot is the whole programme. | 2 ac | 60 / 20 / 20 ft | 35 ft | No |
| Residential Agricultural 1 (RA-1) — a density of 1 LOT PER ACRE, not a flat lot minimum. Lot width 50 ft at the right-of-way and 150 FT AT THE BUILDING LINE (the recorded figure). Front setback 60 ft on town and county roads and 80 ft on a state road; side 20 ft; rear 20 ft; height 2 1/2 stories or 35 feet — dimensionally identical to RA-5 and RA-2 in every respect except density and building-line width, which is the clean pattern in this town: Mendon varies how much land a lot needs and how wide it must be where the house sits, and holds the envelope constant. NO LOT COVERAGE IS STATED so maxLotCoverage is null by design; the schedule carries only a MINIMUM habitable floor area of 1,200 sf one-storey and 1,500 sf otherwise, a house-size floor rather than a ceiling. NOTE THAT THE 1,500 SF FLOOR IS UNCHANGED FROM RA-5 EVEN THOUGH THE LAND REQUIREMENT HAS FALLEN BY FOUR FIFTHS — a one-acre RA-1 lot must deliver exactly the same house as a five-acre RA-5 lot. Like RA-2, RA-1 permits no tourist home, no bed-and-breakfast, no residential conversion and no multi-unit form; it is single-dwelling-per-lot with no exceptions. | 1 ac | 60 / 20 / 20 ft | 35 ft | No |
| Residential Suburban 30 (RS-30) — a density of 1 LOT PER 30,000 SQUARE FEET (0.69 acres), the town's smallest-lot district and the ONLY district in Mendon where any additional density is available. Lot width 50 ft at the right-of-way and 100 FT AT THE BUILDING LINE (the recorded figure). Front setback 60 ft on town and county roads and 80 ft on a state road; SIDE 15 FT — the only district that departs from the town-wide 20 ft side yard; rear 20 ft; height 2 1/2 stories or 35 feet. RS-30 IS THE ONLY MENDON DISTRICT THAT STATES A LOT COVERAGE AND IT IS RECORDED: 25% of the lot. The schedule's shared column reads '1 story: 1,000 ~ Other: 1,200 ~ 25% coverage of lot', so RS-30 carries BOTH a minimum habitable floor area (1,000 sf one-storey, 1,200 sf otherwise — lower than the RA districts' 1,200/1,500) AND a genuine 25% coverage ceiling. Every other district in the town gives floor area only, which is why their coverage is null; do not read those nulls as a missing 25%. EVERY ROUTE TO A SECOND UNIT IN MENDON IS CONCENTRATED HERE, all by Planning Board special use permit under Article VII: RESIDENTIAL CONVERSIONS (the town's de facto ADU, available in no other district), apartment houses, townhouse clusters, multiple-dwelling units and dwelling groups, condominiums and cooperatives, plus tourist homes and bed-and-breakfast establishments. | 0.6887 ac | 60 / 15 / 20 ft | 35 ft | Special permit |
ADUs vs. short-term rentals in Mendon
Short-term rentals allowed with registration for Town of Mendon. MENDON HAS A FULL STANDALONE SHORT-TERM RENTAL LAW WITH AN OPERATING PERMIT, AND IT IS NOT IN THE ZONING CHAPTER — Ch. 208 Short-Term Rentals, §§ 208-1 to 208-16 (guid 42871418, ~32,000 characters, 14 sections). THIS IS THE SECOND CONFIRMED INSTANCE OF THE GATES Ch. 148 PATTERN IN MONROE and it is the reason the whole-code sweep is mandatory: a search of Mendon's Ch. 260 Zoning alone returns nothing for short-term rental and would have produced a false 'no regime' finding. § 208-5 REQUIRES A REVOCABLE SHORT-TERM RENTAL OPERATING PERMIT before a property may be used as an STR at all, granted 'in accordance with the Schedule of Zoning Districts' at § 208-6 — so WHICH DISTRICTS PERMIT AN STR IS SET BY THAT SCHEDULE. Permit mechanics: a NEW permit is valid for a maximum of ONE year and a RENEWAL for a maximum of TWO; all permits expire 31 December of the relevant calendar year regardless of when issued; renewals are filed at the Town of Mendon Building Department and must be received by 1 DECEMBER or the application is treated as new; and THE PERMIT IS NONTRANSFERABLE, so a purchaser of an operating STR must apply afresh and cannot rely on the seller's permit — a material diligence point on any Mendon acquisition premised on rental income. § 208-7 sets property standards that are life-safety rather than dimensional: full compliance with the NYS Uniform Fire Prevention and Building Code and the Town Code with any pre-existing deficiencies corrected BEFORE issuance, a working smoke detector in every sleeping room plus one per floor, carbon monoxide detectors, evacuation procedures posted in each sleeping room and in the kitchen and main living room, and portable fire extinguishers on each floor and in the kitchen under NY Fire Code § 906 with an inspection record produced at application. §§ 208-10 to 208-13 carry compliance, penalties, suspension and revocation, renewal and appeals. SEPARATELY AND NOT THE SAME THING, the zoning chapter permits TOURIST HOMES AND BED-AND-BREAKFAST ESTABLISHMENTS by SPECIAL USE PERMIT from the Planning Board, but only in RA-5 and RS-30 — not in RA-2 or RA-1. A bed-and-breakfast is an owner-present lodging use on a different track from the Ch. 208 STR permit and the two should not be conflated. New York State's 2025 statewide short-term rental registry (Ch. 99 of the Laws of 2025) obliges every host to register in addition to the Town permit. Confirm with the Building Department at (585) 624-6066. These are separate questions from whether you can build an ADU — a unit you're allowed to add isn't automatically one you're allowed to rent nightly, so check both.
Good to know
- Residential lot minimum0.6887–5 ac — an ADU still has to fit the district's lot and setback envelope.
- UtilityRG&E territory.
- Building dept(585) 624-6066
- Last reviewed2026-08-13
ADU FAQ — Mendon, NY
Are ADUs allowed in Mendon, NY?
Town of Mendon has 4 districts. 3 districts prohibit ADUs, 1 requires a special-use permit. Check your address with the free ADU checker, or confirm with the building department at (585) 624-6066.
Do I need a special permit for an ADU in Mendon?
It depends on the district: 1 of 4 require a special-use permit, the rest do not. Check the district that applies to your parcel before you design.
Can I use an ADU as a short-term rental in Mendon?
Short-term rentals allowed with registration for Town of Mendon. ADU occupancy and short-term-rental rules are separate: an ADU you can build isn't automatically one you can rent nightly. Confirm both before you count on STR income.
What an ADU costs to build in Mendon
Permission is one question and budget is another. An 800 sq ft accessory unit here runs roughly $200k–260k at a standard finish, and the per-square-foot rate comes in above a full house because the kitchen, bath, panel and heating plant cost the same either way. See the full cost to build an ADU in Mendon, priced by size.
More on Mendon: Full zoning for new construction · ADU build cost · House build cost · All Monroe County towns
ADU information for Town of Mendon is compiled from the municipal code (last reviewed 2026-08-13) and provided for decision-support only — not legal or architectural advice. ADU eligibility, size, owner-occupancy and permit conditions vary by district and often carry exceptions; verify with the building department at (585) 624-6066 before relying on any answer. Source: Offsite / Aldo zoning dataset, municipalData.js.