Can you build an ADU in Elmsford, NY?

Residence R-O District: one family - The 5 ft side yard and 12 ft combined shown are the floor, for a lot 40 ft wide or less. Each foot of width above 40 ft adds 1 inch to each side yard and 3 inches to the combined total, up to a lot width of 60 ft (§ 335-17A).

• The 20 ft front yard is a mean depth (§ 335-15A(1)).
• Where the block has a pronounced uniformity of deeper front yards, a new building must match it, though never beyond 40 ft.
• The Board of Appeals may allow a shallower front yard where the block is uniformly shallower.
• House bulk here is capped by a floor area ratio that falls as the lot grows, from 0.450 below 3,500 square feet to 0.338 at 10,000 square feet or more (§ 335-4S).
• A residential lot must abut at least 50 ft on a street at least 30 ft wide, or reach one by an unobstructed easement at least 15 ft wide (§ 335-4F(1)).
• An accessory building may cover at most 30% of the required rear yard, and none in a residence district may exceed two stories (§ 335-4N(1)).

Residence R-1 District: one family - The 5 ft side yard and 12 ft combined shown are the floor, for a lot 40 ft wide or less. Each foot of width above 40 ft adds 1 inch to each side yard and 3 inches to the combined total, up to a lot width of 60 ft (§ 335-17A).

• The 20 ft front yard is a mean depth (§ 335-15A(1)).
• Where the block has a pronounced uniformity of deeper front yards, a new building must match it, though never beyond 40 ft.
• The Board of Appeals may allow a shallower front yard where the block is uniformly shallower.
• The Board of Appeals may permit a new two-family dwelling as a special exception after a public hearing, and the lot then needs 10,000 square feet and 100 ft of frontage (§ 335-22F).
• House bulk here is capped by a floor area ratio that falls as the lot grows, from 0.450 below 3,500 square feet to 0.338 at 10,000 square feet or more (§ 335-4S).
• A residential lot must abut at least 50 ft on a street at least 30 ft wide, or reach one by an unobstructed easement at least 15 ft wide (§ 335-4F(1)).

Residence R-2 District: two families - The 5 ft side yard shown is the floor, for a lot 25 ft wide or less. Each foot of width above 25 ft adds 1 inch, up to a lot width of 50 ft, and each foot of building height above 40 ft adds 2 inches more (§ 335-17B).

• The lot minimum and width shown are the two-family standard; a one-family house needs only 5,000 square feet and 50 ft of frontage (§ 335-4F(3)).
• The 20 ft rear yard grows by 4 inches for each foot of building height above 30 ft (§ 335-16B).
• A new two-family house, or converting a one-family house to two units, needs a special permit from the Board of Trustees that runs five years and ends on a sale (§ 335-6B).
• House bulk here is capped by a floor area ratio that falls as the lot grows, from 0.450 below 3,500 square feet to 0.338 at 10,000 square feet or more (§ 335-4S).
• Parking for a two-family house must sit in a side or rear yard, or behind the 20 ft setback (§ 335-4F(6)).
• The 20 ft front yard is a mean depth (§ 335-15A(1)).

Residence R-3 District: three or more families - The figures shown are the multifamily controls, so the side and rear yards belong to a multifamily building. A one-family house here needs only 5,000 square feet and 50 ft of frontage, and the district's own height limit is 48 ft.

• Each dwelling unit in a multifamily building needs 2,500 square feet of land, and the lot must be at least 10,000 square feet with 100 ft of frontage (§ 335-4F(4)).
• A multifamily dwelling is held to 2 1/2 stories or 35 ft, below the 48 ft the district otherwise allows (§ 335-7C).
• A multifamily dwelling for three or more families may be built only here and in the Business District (§ 335-7B).
• Every multifamily development must set aside a recreation area of at least 10% of the site, or pay a fee in lieu (§ 335-28G).
• A one or two family house here also carries the floor area ratio ladder, which falls from 0.450 below 3,500 square feet to 0.338 at 10,000 square feet or more (§ 335-4S).
• Site plan review by the Board of Trustees reaches every building other than a one or two family residence (§ 335-28B).

Residential Cluster Development (RCD) District - The front, side and rear yards are those set in § 335-8C(2)(e) for RCD, not the general yard rules.

Business District - A multifamily dwelling for three or more families may be built here on site plan approval, on a lot of at least 40,000 square feet, or 15,000 square feet where the lot is bordered by two or more streets, with building coverage capped at 40%.

• Each dwelling unit needs 1,200 square feet of land, or 2,000 square feet on a lot smaller than 40,000 square feet.
• The 150 ft height applies only where the building meets the state building code, stands on a lot at least 100 ft wide and fronts a public street or equivalent open space (§ 335-14B).
• No front, side or rear yard is required, but a side yard that is provided must meet the R-2 sliding scale, at least 5 ft and rising with lot width.
• A rear yard that is provided must be at least 10 ft, or follow the R-2 rear yard rule where a residence use occupies part of the building.
• A lot whose rear line bounds a residence district owes half the R-2 rear depth above the ground story.
• A lot line bordering a residence district takes evergreen screening at least 5 ft high, or an approved wall or fence.

Central Business District, Light Industrial District - No front, side or rear yard is required, but a side yard that is provided must meet the R-2 sliding scale, at least 5 ft and rising with lot width.

• A rear yard that is provided must be at least 10 ft, or follow the R-2 rear-yard rule where a residence use occupies part of the building.
• A lot whose rear line bounds a residence district owes half the R-2 rear depth above the ground story.

Limited Office Use District - The 80 ft of frontage must be on a state highway, and the front and rear yards shown are mean depths. A side yard that abuts a street must equal the required front yard instead of the 15 ft shown.

• The 15 ft side yard does not apply where that side adjoins off-street parking in an adjacent residence district (§ 335-12B(3)(e)).
• The height limit does not reach ventilators, skylights, water tanks, bulkheads, chimneys, cooling towers and similar roof appurtenances.
• The district is mapped to a single site of about 3 acres at Knollwood Road and Knollwood Drive, and is meant only for state highway frontage within half a mile of an I-287 interchange.
• A self storage facility carries its own dimensions: a lot of at least half an acre with 100 ft of width, depth and frontage, a 10 ft front yard, no side or rear yard, and five stories or 70 ft.
• Every site plan needs Board of Trustees approval, and parking runs one space for each 400 square feet of gross floor area (§ 335-12B(4)).
• All of the lot not built on or surfaced must be landscaped, with evergreen screening where a lot line meets a residence district boundary.

Unzoned (Highway ROW Lands) - This is not a zoning district. It covers highway right-of-way parcels outside the mapped zoning districts.