Can you build an ADU in Henrietta, NY?

R-1-20 Residential - The 1,400 sq ft minimum applies to a one-storey ranch or Raised Ranch B; a two-storey house must total 2,000 sq ft, with at least 1,000 on the first floor and 600 on the second. The 25% coverage cap counts principal and accessory buildings together.

• A Raised Ranch A, a one-and-a-half-storey house or a Split-Level A must be at least 1,200 sq ft under § 295-11.
• Garages, porches and areaways are excluded when the minimum building size is measured.
• Height is capped at two stories of any kind above the basement, with a separate 21 ft limit measured from the top of the first floor of the first story to the ceiling of the second story (§ 295-8).
• Accessory buildings other than garages may cover no more than 1% of the lot in total, and no more than two individual accessory buildings are permitted.
• In a subdivision, the Planning Board requires enough variation in dwelling types, exterior architecture or floor plans to avoid a uniform or monotonous appearance.

R-1-15 Residential - Height is capped at two stories above the basement, and separately at 21 ft measured inside, from the top of the first floor to the ceiling of the second story, rather than from grade to ridge (§ 295-8).

• The story count, rather than the 21 ft figure, is the height standard that binds.
• The 25% building coverage cap counts the house and accessory buildings together.
• Accessory buildings other than garages may cover no more than 1% of the lot in total, and no more than two individual accessory buildings are allowed.
• Minimum building size varies by house type under § 295-11: 850 sq ft for a Raised Ranch A, one-and-a-half story or Split-Level A, and 1,040 sq ft for a one-story ranch or Raised Ranch B.
• A two-story house must total 1,320 sq ft, with at least 660 sq ft on the first floor and 264 sq ft on the second.

R-2-15 Residential - The figures shown apply to a single-family home. A two-family use has a separate, larger set of dimensional requirements, and this is the town's only residential district reaching a multiple dwelling.

• A two-family unit takes 15,000 sq ft and 100 ft of width against the 12,000 sq ft and 75 ft a single-family needs, a quarter more land and a third more frontage.
• A multiple dwelling is reachable by Town Board special permit at up to 12 units per acre, with 60 ft from every property line, or 30 ft beside commercial land, and 35 ft of height.
• No more than 35% of such a parcel may be built on, green space excludes slopes over 15%, and habitable area runs 500 sq ft for a studio, 600 for a one-bedroom, 800 for a two-bedroom and 950 for three.
• § 295-8 caps a residential structure at two stories of any kind above the basement and at 21 ft measured from the top of the first floor to the ceiling of the second story, an interior measurement.
• The 25% building coverage cap counts principal and accessory buildings together; accessory buildings, garages excluded, may not cover more than 1% of the lot, and no more than two are permitted.
• The 810 sq ft applies to a one-storey ranch or Raised Ranch B; a Raised Ranch A, one-and-a-half-storey or Split-Level A needs 672 sq ft, and a two-storey 960 sq ft total, 480 on the first floor.

Rural Residential — served by municipal water and sewer - The two-acre minimum applies only to a lot with both municipal water and sewer that sits outside a state-certified, county-adopted agricultural district under § 295-10.1F. A lot missing either condition falls to the five-acre tier.

• Senior housing is the only multiple-dwelling form permitted here, capped at 6 units per acre, with 60 ft from every property line, 30 ft beside commercial land, and 40 ft between buildings.
• No more than 35% of such a parcel may be built on, and habitable area runs 500 sq ft for a studio, 600 for a one-bedroom, 800 for a two-bedroom and 950 for a three-bedroom.
• Each lot must also contain at least 10,000 sq ft of contiguous area for building and yard free of wetlands, surface water and slopes over 15%, so a constrained two-acre lot can fail even at full size.
• The front setback shown is for a town or private road; a lot on a county or state road owes 50 ft. Side yards are not equal: 10 ft on one side and 15 ft on the other.
• Coverage counts principal and accessory buildings together, accessory buildings may not exceed 1% of the lot and no more than two are permitted; the lot minimum may be smaller under Article IXB.
• § 295-8 caps a residential structure at two storeys above the basement, plus 21 ft measured from the top of the first floor to the ceiling of the second storey, an interior measurement.

Rural Residential — not served by both municipal water and sewer - Each lot must contain at least 20,000 sq ft of contiguous area for building and yard, free of wetlands, surface water and slopes over 15%. A lot inside a state-certified, county-adopted agricultural district also needs five acres, even if fully serviced (§ 295-10.1F).

• Senior housing is the only multiple-dwelling form permitted here, capped at 6 units per acre by Town Board special permit, with 60 ft from every property line, or 30 ft beside commercial land.
• No more than 35% of such a parcel may be built on, and habitable area runs 500 sq ft for a studio, 600 for a one-bedroom, 800 for a two-bedroom and 950 for a three-bedroom.
• Side yards are not symmetric, 10 ft on one side and 20 ft on the other, and a lot on a county or state road owes a 60 ft front setback rather than the 40 ft shown.
• The lot minimum may be smaller under the open space incentive in Article IXB, and minimum building size follows the R-1-15 schedule: 1,040 sq ft for a one-story ranch and 1,320 sq ft for a two-story.
• Building coverage counts principal and accessory buildings together. Accessory buildings, garages excluded, may cover no more than 1% of the lot, and no more than two are permitted.
• § 295-8 also limits a residential building to 21 ft measured from the top of the first floor of the first story to the ceiling of the second story, an interior measurement, not grade to ridge.