What it costs to build an ADU in Scarsdale, NY

Residence AA-1 District - Coverage is set by lot size rather than by district: above one acre a lot may carry 13,100 sq ft of structures and impervious surfaces plus 10% of the area above one acre, and 4,642 sq ft of buildings plus 4% of that same excess (§ 310-22).

• At least 65% of the lot must stay as required open space, the part that is vegetated and open to the sky and carries no structure, parking or paving (§ 310-23.1).
• A house may reach 36 ft, and no higher, by meeting the sky exposure plane if it stands farther back than the required 75 ft from the front lot line (§ 310-25D).
• On a corner lot the building sets back 65 ft from the side street line, and a lot fronting a county or state highway sets back 10 ft more in front (§ 310-53, § 310-40).
• Floor area for a house is capped by a ratio that slides with lot size, and at 50,000 sq ft and above it is 0.14 of the lot (§ 310-102).
• No more than 10% of the lot area counted toward the minimum may be water, floodplain or a retention basin (§ 310-14B).
• A principal building one story high sets back 25 ft from the rear lot line rather than 30 ft (§ 310-43A(2)).

Residence A-1 District - Coverage is set by lot size rather than by district: a one acre lot may carry 6,000 sq ft of structures and impervious surfaces plus 30% of the area above 20,000 sq ft, and 3,700 sq ft of buildings plus 4% of that same excess (§ 310-22).

• At least 55% of the lot must stay as required open space, the part that is vegetated and open to the sky and carries no structure, parking or paving (§ 310-23.1).
• Floor area for a house is capped by a ratio that slides with lot size, from 0.425 at 5,000 sq ft and under to 0.14 at 50,000 sq ft and above (§ 310-102).
• Each foot of side yard beyond the minimum buys another 100 sq ft of floor area above that cap, up to 800 sq ft (§ 310-104).
• On a corner lot the building sets back 40 ft from the side street line, and a lot fronting a county or state highway sets back 10 ft more in front (§ 310-53, § 310-40).
• Where the lot is less than 120 ft deep the front setback drops one foot for each foot of shortfall, but never below 30 ft (§ 310-18).
• A principal building one story high sets back 25 ft from the rear lot line rather than 30 ft (§ 310-43A(2)).

Residence A-2 District - Coverage is set by lot size rather than by district: a 20,000 sq ft lot may carry 5,250 sq ft of structures and impervious surfaces plus 15% of the area above 15,000 sq ft, and 3,100 sq ft of buildings plus 12% of that same excess (§ 310-22).

• At least 50% of the lot must stay as required open space, the part that is vegetated and open to the sky and carries no structure, parking or paving (§ 310-23.1).
• Floor area for a house is capped by a ratio that slides with lot size, from 0.425 at 5,000 sq ft and under to 0.14 at 50,000 sq ft and above (§ 310-102).
• Each foot of side yard beyond the minimum buys another 100 sq ft of floor area above that cap, up to 400 sq ft (§ 310-104).
• On a corner lot the building sets back 30 ft from the side street line, and a lot fronting a county or state highway sets back 10 ft more in front (§ 310-53, § 310-40).
• Where the lot is less than 110 ft deep the front setback drops one foot for each foot of shortfall, but never below 30 ft (§ 310-18).
• A principal building one story high sets back 25 ft from the rear lot line rather than 30 ft (§ 310-43A(2)).

Residence A-2a District - Coverage is set by lot size rather than by district: a 15,000 sq ft lot may carry 4,000 sq ft of structures and impervious surfaces plus 25% of the area above 10,000 sq ft, and 2,500 sq ft of buildings plus 12% of that same excess (§ 310-22).

• At least 45% of the lot must stay as required open space, the part that is vegetated and open to the sky and carries no structure, parking or paving (§ 310-23.1).
• Floor area for a house is capped by a ratio that slides with lot size, from 0.425 at 5,000 sq ft and under to 0.14 at 50,000 sq ft and above (§ 310-102).
• Each foot of side yard beyond the minimum buys another 100 sq ft of floor area above that cap, up to 350 sq ft (§ 310-104).
• On a corner lot the building sets back 30 ft from the side street line, and a lot fronting a county or state highway sets back 10 ft more in front (§ 310-53, § 310-40).
• An accessory building sets back at least 5 ft from the rear lot line, and one more than 80 ft from any street line may come within 10 ft of a side lot line that is not a street line (§ 310-47A).
• A principal building one story high sets back 25 ft from the rear lot line rather than 30 ft (§ 310-43A(2)).

Residence A-3 District - Coverage is set by lot size rather than by district: a 10,000 sq ft lot may carry 3,000 sq ft of structures and impervious surfaces plus 40% of the area above 7,500 sq ft, and 2,100 sq ft of buildings plus 16% of that same excess (§ 310-22).

• At least 40% of the lot must stay as required open space, the part that is vegetated and open to the sky and carries no structure, parking or paving (§ 310-23.1).
• Floor area for a house is capped by a ratio that slides with lot size, from 0.425 at 5,000 sq ft and under to 0.14 at 50,000 sq ft and above (§ 310-102).
• Each foot of side yard beyond the minimum buys another 100 sq ft of floor area above that cap, up to 300 sq ft (§ 310-104).
• On a corner lot the building sets back 20 ft from the side street line, and a lot fronting a county or state highway sets back 10 ft more in front (§ 310-53, § 310-40).
• An accessory building sets back at least 5 ft from the rear lot line, and one more than 60 ft from any street line may come within 8 ft of a side lot line that is not a street line (§ 310-47A).
• A principal building one story high sets back 25 ft from the rear lot line rather than 30 ft (§ 310-43A(2)).

Residence A-4 District - Coverage is set by lot size rather than by district: a 7,500 sq ft lot may carry 2,250 sq ft of structures and impervious surfaces plus 30% of the area above 5,000 sq ft, and 1,500 sq ft of buildings plus 24% of that same excess (§ 310-22).

• At least 35% of the lot must stay as required open space, the part that is vegetated and open to the sky and carries no structure, parking or paving (§ 310-23.1).
• Floor area for a house is capped by a ratio that slides with lot size, from 0.425 at 5,000 sq ft and under to 0.14 at 50,000 sq ft and above (§ 310-102).
• Each foot of side yard beyond the minimum buys another 100 sq ft of floor area above that cap, up to 225 sq ft (§ 310-104).
• On a corner lot the building sets back 15 ft from the side street line, and a lot fronting a county or state highway sets back 10 ft more in front (§ 310-53, § 310-40).
• A detached private garage for not more than two cars may stand on a side lot line that is not a street line where it is built across a common line by agreement between the two owners (§ 310-48C).
• A principal building one story high sets back 25 ft from the rear lot line rather than 30 ft (§ 310-43A(2)).

Residence A-5 District - Coverage is set by lot size rather than by district: a lot of 5,000 sq ft or less is capped at 45% of its area for structures and impervious surfaces and 30% for buildings, and above that the caps become 2,250 sq ft plus 30% and 1,500 sq ft plus 24% (§ 310-22).

• At least 30% of the lot must stay as required open space, the part that is vegetated and open to the sky and carries no structure, parking or paving (§ 310-23.1).
• Floor area for a house is capped by a ratio that slides with lot size, from 0.425 at 5,000 sq ft and under to 0.14 at 50,000 sq ft and above (§ 310-102).
• Each foot and a half of side yard beyond the minimum buys another 100 sq ft of floor area above that cap, up to 200 sq ft (§ 310-104).
• On a corner lot the building sets back 15 ft from the side street line, and a lot fronting a county or state highway sets back 10 ft more in front (§ 310-53, § 310-40).
• A detached private garage for not more than two cars may stand on a side lot line that is not a street line where it is built across a common line by agreement between the two owners (§ 310-48C).
• A principal building one story high sets back 25 ft from the rear lot line rather than 30 ft (§ 310-43A(2)).

Residence C District - An apartment house or hotel needs a side yard of at least 15 ft. The 20 ft rear yard applies to a 3-story building; anything shorter needs at least 15 ft (§ 310-44).

• On a lot that has been less than 100 ft deep since 1922 the rear setback drops six inches for each foot of shortfall, and never below 15 ft (§ 310-44).
• An accessory building more than 60 ft from any street may sit as close as 3 ft to a side line.
• In place of a coverage percentage the district requires one square foot of open space on the lot for every two square feet of gross floor area used for residence purposes (§ 310-27B).
• Accessory buildings, private garages included, may cover no more than 15% of the lot (§ 310-30).
• A multifamily dwelling here is limited to one family for each 2,000 sq ft of the property occupied, counting the yards and open spaces used with the buildings (§ 310-32).

Business A District - The front yard depends on street width: at least 10 ft on a street under 60 ft wide, at least 5 ft on one 60 to 70 ft wide, and 0 ft on a street 70 ft wide or more.

• No side yard is required except along a street line, where the front yard rule applies, or on a residence-district boundary, where it is at least 10 ft.
• An apartment house, hotel or building over 2 residential stories needs at least 15 ft on a side line that is not a street line.
• No rear setback is required where the rear line adjoins an operating railroad right-of-way.
• A building used partly for residence sets back 30 ft at and above the lowest residence story, less extra depth given to the business part; units put into an existing building are exempt (§ 310-37).
• A multifamily dwelling here is limited to one family for each 2,000 sq ft of the property occupied, counting the yards and open spaces used with it (§ 310-32).

Business C District - No side yard is required, but a residence district boundary at the side or rear takes a 50 ft yard with its first 20 ft landscaped, and the first 20 ft of the 50 ft front yard must be landscaped too (§ 310-46, § 310-38).

• No single store in any building may have a floor larger than 12,000 sq ft (§ 310-29B).
• Residences are not permitted, and the district otherwise takes the Residence A and Business A use lists (§ 310-13A).
• The part of a building nearest the rear lot line may stand closer than 10 ft where it is at least 50 ft from the front lot line (§ 310-45).
• No rear setback is required where the rear lot line adjoins the right of way of an operating railroad (§ 310-45).
• Where a side lot line is a street line the building sets back from it as it would from a front lot line (§ 310-55A).

Planned Unit Development - 0.8 to 1.4 - The 0.8 floor area ratio is limited entirely to residential use, and no less than 10% of the residential floor area must be senior citizen housing (§ 310-28.1A(6)(b)).

• The ratio may rise to 1.4, of which no more than 14% may be nonresidential, only on a Village Board incentive density special permit, and here only for short term public parking (§ 310-28.1B).
• Under that same special permit the highest point of the roof may instead rise to an elevation of 218 ft above sea level in place of the 46 ft limit (§ 310-28.1A(6)(a)).
• Ground floor retail stores, restaurants other than fast food, banks, personal service establishments and public and semipublic uses need that special permit as well (§ 310-12B(6)(b)[1]).
• No minimum front, side or rear yard is established here; the Planning Board fixes the setbacks it finds necessary at site plan review and may require landscaping within them (§ 310-37.1).
• Where a side or rear yard adjoins a residential-use lot in a Residence A or C District, the building sets back 1 ft for every foot it rises above existing grade at that lot line (§ 310-55B).
• A multifamily dwelling here is limited to one family for each 2,000 sq ft of the property occupied, counting the yards and open spaces used with the buildings (§ 310-32).

Planned Unit Development - 1.0 - This district publishes no height in feet. The highest point of any roof may reach an elevation of 184 ft above sea level, or 204 ft for a building south of the Popham Road Bridge (§ 310-28.1A(7)(a)).

• The 1.0 floor area ratio applies to the entire development site, and south of the Popham Road Bridge no more than 10% of it may be put to nonresidential use (§ 310-28.1A(7)(b)).
• No less than 10% of the residential floor area must be senior citizen housing, meaning a household with at least one member aged 65 or over when it first occupies the unit (§ 310-12B(7)(b)[2]).
• Retail, personal service, restaurants other than fast food, banks and professional offices are limited to ground floor levels in a building containing residences (§ 310-12B(7)(b)[1]).
• Parking is permitted only on a Village Board special permit, and the Village Board may take cash, or land and cash, in place of some or all of the required off street parking (§ 310-70).
• No minimum front, side or rear yard is established here; the Planning Board fixes the setbacks it finds necessary at site plan review and may require landscaping within them (§ 310-37.1).
• Where a side or rear yard adjoins a residential-use lot in a Residence A or C District, the building sets back 1 ft for every foot it rises above existing grade at that lot line (§ 310-55B).

Village Center Office - 0.8 - The Planning Board sets front, side and rear setbacks case by case at site plan review, for design, safety and screening from neighboring residence districts.

• A side or rear yard next to a residential-use lot in a residence district must be at least 1 ft deep for every 1 ft the building rises above existing grade at that lot line.
• Off street parking must be met on private property for any new building and for any conversion from residential to commercial use (§ 310-12B).
• A service station may have no canopy larger than its fuel dispensers need and no more than 50 sq ft of prepackaged merchandise unrelated to servicing vehicles (§ 310-12B(5)(b)).

Village Center Office - 2.0 - The Planning Board sets front, side and rear setbacks case by case at site plan review, for design, safety and screening from neighboring residence districts.

• A side or rear yard next to a residential-use lot in a residence district must be at least 1 ft deep for every 1 ft the building rises above existing grade at that lot line.
• Off street parking must be met on private property for any new building and for any conversion from residential to commercial use (§ 310-12B).
• Permitted uses are professional, medical, dental, administrative and business offices, public and semipublic uses, real estate offices, travel agencies and residences (§ 310-12B(4)(b)).

Village Center Retail - 0.8 - The Planning Board sets front, side and rear setbacks case by case at site plan review, for design, safety and screening from neighboring residence districts.

• A side or rear yard next to a residential-use lot in a residence district must be at least 1 ft deep for every 1 ft the building rises above existing grade at that lot line.
• Off street parking must be met on private property for any new building and for any conversion from residential to commercial use (§ 310-12B).
• Permitted uses are retail stores, personal service establishments, restaurants other than fast food, and public and semipublic uses, with no drive-up facility of any kind (§ 310-12B(3)(b)).

Village Center Retail - 1.0 - The Planning Board sets front, side and rear setbacks case by case at site plan review, for design, safety and screening from neighboring residence districts.

• A side or rear yard next to a residential-use lot in a residence district must be at least 1 ft deep for every 1 ft the building rises above existing grade at that lot line.
• Off street parking must be met on private property for any new building and for any conversion from residential to commercial use (§ 310-12B).
• Ground floor uses are retail stores, personal service establishments, restaurants other than fast food, and public and semipublic uses, with no drive-up facility of any kind (§ 310-12B(2)(b)).

Village Center Retail - 2.0 - The Planning Board sets front, side and rear setbacks case by case at site plan review, for design, safety and screening from neighboring residence districts.

• A side or rear yard next to a residential-use lot in a residence district must be at least 1 ft deep for every 1 ft the building rises above existing grade at that lot line.
• Off street parking must be met on private property for any new building and for any conversion from residential to commercial use (§ 310-12B).
• Ground floor uses take no drive-up facility of any kind, and upper floors add professional, medical, dental, business and administrative offices and residences (§ 310-12B(1)(b)).

Buffer Parking District - B-P allows an outdoor parking lot on land next to a business district, only by Planning Board special permit with a site plan (§ 310-10). The Planning Board sets screening, landscaping and layout conditions case by case.

• The site plan must show no display or advertising on the parking lot, and must provide the landscaping and screening the Planning Board requires for the neighborhood (§ 310-10).