What it costs to build an ADU in North Castle, NY

Golf Course Community Floating Overlay District - The figures shown are the R-2A standards, which govern the R-2A uses that remain permitted here. A golf course community, the overlay's own principal use, has its lots and yards set by the Planning Board at subdivision instead.

• For a golf course community, density is one density unit per 133,000 sq ft and one dwelling unit per 1.8 acres of aggregate lot area (§ 355-32D).
• For that community, 3.5% building coverage and a limit of 3 stories and 39 1/2 ft to the mean level of the primary roof apply to the whole overlay area as one lot.
• The overlay may be mapped only on R-2A land of at least 150 acres holding an 18-hole golf course, and only more than 100 ft inside its perimeter (§ 355-32B).
• A unit in that community needs at least 450 sq ft for an efficiency, 700 for one bedroom, 900 for two and 1,100 for three (§ 355-32D(4)).
• Units in that community must all connect to public or central water and sewer (§ 355-32F).

One-Family Residence District - A new lot needs a contiguous buildable area clear of wetlands, water bodies, floodplains and steep slopes: at least 30,000 sq ft with on-lot septic and a well, 25,000 with septic and central water, 20,000 with central sewer and a well, or 18,000 with central sewer and water.

• Street frontage must be at least 150 ft, which the Planning Board may reduce to 25 ft on a lot at the turnaround of a dead-end street.
• Gross floor area and gross land coverage of a one- or two-family dwelling are capped on a sliding scale by lot size (§ 355-26B and C), and a new lot is measured on net lot area.
• The Planning Board may approve a conservation subdivision with lots of one acre or half the district minimum, whichever is less, and no more lots than a conventional layout would yield.
• On a corner lot the side yard on the side street must equal the required front yard (§ 355-15).
• A one-story accessory building under 800 sq ft, other than a stable, may sit at half the required side or rear distance, but no nearer the street than the front yard.
• From the lowest grade along an exterior wall, the vertical distance to the roof point where height is measured may not exceed 36 ft (§ 355-26D).

One-Family Residence District - A new lot needs a contiguous buildable area clear of wetlands, water bodies, floodplains and steep slopes: at least 35,000 sq ft with on-lot septic and a well, 30,000 with septic and central water, 22,000 with central sewer and a well, or 20,000 with central sewer and water.

• Street frontage must be at least 150 ft, which the Planning Board may reduce to 25 ft on a lot at the turnaround of a dead-end street.
• Gross floor area and gross land coverage of a one- or two-family dwelling are capped on a sliding scale by lot size (§ 355-26B and C), and a new lot is measured on net lot area.
• The Planning Board may approve a conservation subdivision with lots of one acre or half the district minimum, whichever is less, and no more lots than a conventional layout would yield.
• On a corner lot the side yard on the side street must equal the required front yard (§ 355-15).
• A one-story accessory building under 800 sq ft, other than a stable, may sit at half the required side or rear distance, but no nearer the street than the front yard.
• From the lowest grade along an exterior wall, the vertical distance to the roof point where height is measured may not exceed 38 ft (§ 355-26D).

One-Family Residence District - A new lot needs a contiguous buildable area clear of wetlands, water bodies, floodplains and steep slopes: at least 40,000 sq ft with on-lot septic and a well, 35,000 with septic and central water, 25,000 with central sewer and a well, or 22,000 with central sewer and water.

• Street frontage must be at least 250 ft, which the Planning Board may reduce to 25 ft on a lot at the turnaround of a dead-end street.
• Gross floor area and gross land coverage of a one- or two-family dwelling are capped on a sliding scale by lot size (§ 355-26B and C), and a new lot is measured on net lot area.
• The Planning Board may approve a conservation subdivision with lots of one acre or half the district minimum, whichever is less, and no more lots than a conventional layout would yield.
• On a corner lot the side yard on the side street must equal the required front yard (§ 355-15).
• A one-story accessory building under 800 sq ft, other than a stable, may sit at half the required side or rear distance, but no nearer the street than the front yard.
• From the lowest grade along an exterior wall, the vertical distance to the roof point where height is measured may not exceed 38 ft (§ 355-26D).

Multifamily Residence District - The figures shown are for an R-MF development site as a whole, and density is capped at one density unit per 25,000 sq ft of net lot area (§ 355-24B). Lots for the attached and detached units inside the development have their own smaller figures.

• Each yard doubles along a common property line with land in an adjoining single-family residence district.
• A lot for an attached unit inside the development needs at least 35 ft of width, 80 ft of depth and 25 ft of street frontage, with a 20 ft front yard, 15 ft rear and 35% building coverage.
• One side yard of an attached unit may be 0 ft where the two total at least 10 ft.
• A lot for a detached unit needs at least 65 ft of width, 80 ft of depth and 25 ft of street frontage, with a 20 ft front yard, 10 ft side, 25 ft both sides and 15 ft rear.
• At least half the gross site area must stay permanent open space free of buildings and parking (§ 355-24F), and every dwelling must connect to public water and sewer (§ 355-24D).
• A development of 10 or more units must make at least 10% of them affordable AFFH units (§ 355-24I(1)).

One-Family Residence District - A new lot needs a contiguous buildable area clear of wetlands, water bodies, floodplains and steep slopes: at least 20,000 sq ft with on-lot septic and a well, 16,000 with septic and central water, 13,000 with central sewer and a well, or 12,000 with central sewer and water.

• Street frontage must be at least 125 ft, which the Planning Board may reduce to 25 ft on a lot at the turnaround of a dead-end street.
• Gross floor area and gross land coverage of a one- or two-family dwelling are capped on a sliding scale by lot size (§ 355-26B and C), and a new lot is measured on net lot area.
• The Planning Board may approve a conservation subdivision with lots of one acre or half the district minimum, whichever is less, and no more lots than a conventional layout would yield.
• On a corner lot the side yard on the side street must equal the required front yard (§ 355-15).
• A one-story accessory building under 800 sq ft, other than a stable, may sit at half the required side or rear distance, but no nearer the street than the front yard.
• From the lowest grade along an exterior wall, the vertical distance to the roof point where height is measured may not exceed 34 ft (§ 355-26D).

One-Family Residence District - A new lot needs a contiguous buildable area clear of wetlands, water bodies, floodplains and steep slopes: at least 25,000 sq ft with on-lot septic and a well, 20,000 with septic and central water, 17,000 with central sewer and a well, or 16,000 with central sewer and water.

• Street frontage must be at least 125 ft, which the Planning Board may reduce to 25 ft on a lot at the turnaround of a dead-end street.
• Gross floor area and gross land coverage of a one- or two-family dwelling are capped on a sliding scale by lot size (§ 355-26B and C), and a new lot is measured on net lot area.
• The Planning Board may approve a conservation subdivision with lots of one acre or half the district minimum, whichever is less, and no more lots than a conventional layout would yield.
• On a corner lot the side yard on the side street must equal the required front yard (§ 355-15).
• A one-story accessory building under 800 sq ft, other than a stable, may sit at half the required side or rear distance, but no nearer the street than the front yard.
• From the lowest grade along an exterior wall, the vertical distance to the roof point where height is measured may not exceed 36 ft (§ 355-26D).

One-Family Residence District - A new lot needs a contiguous buildable area clear of wetlands, water bodies, floodplains and steep slopes: at least 22,000 sq ft with on-lot septic and a well, 18,000 with septic and central water, 15,000 with central sewer and a well, or 14,000 with central sewer and water.

• Street frontage must be at least 125 ft, which the Planning Board may reduce to 25 ft on a lot at the turnaround of a dead-end street.
• Gross floor area and gross land coverage of a one- or two-family dwelling are capped on a sliding scale by lot size (§ 355-26B and C), and a new lot is measured on net lot area.
• The Planning Board may approve a conservation subdivision with lots of one acre or half the district minimum, whichever is less, and no more lots than a conventional layout would yield.
• On a corner lot the side yard on the side street must equal the required front yard (§ 355-15).
• A one-story accessory building under 800 sq ft, other than a stable, may sit at half the required side or rear distance, but no nearer the street than the front yard.
• From the lowest grade along an exterior wall, the vertical distance to the roof point where height is measured may not exceed 34 ft (§ 355-26D).

One-Family Residence District - A new lot needs a contiguous buildable area clear of wetlands, water bodies, floodplains and steep slopes: at least 10,000 sq ft with on-lot septic, 9,000 with central sewer and a well, or 8,000 with central sewer and water.

• Street frontage must be at least 100 ft, which the Planning Board may reduce to 25 ft on a lot at the turnaround of a dead-end street.
• Gross floor area and gross land coverage of a one- or two-family dwelling are capped on a sliding scale by lot size (§ 355-26B and C), and a new lot is measured on net lot area.
• The Planning Board may approve a conservation subdivision with lots of one acre or half the district minimum, whichever is less, and no more lots than a conventional layout would yield.
• On a corner lot the side yard on the side street must equal the required front yard (§ 355-15).
• A one-story accessory building under 800 sq ft, other than a stable, may sit at half the required side or rear distance, but no nearer the street than the front yard.
• From the lowest grade along an exterior wall, the vertical distance to the roof point where height is measured may not exceed 34 ft (§ 355-26D).

Two-Family Residence District - A new lot needs a contiguous buildable area clear of wetlands, water bodies, floodplains and steep slopes: at least 5,000 sq ft with on-lot septic and a well, 5,000 with septic and central water, 4,500 with central sewer and a well, or 4,000 with central sewer and water.

• A two-family dwelling may have one third more gross floor area and 25% more gross land coverage than a one-family dwelling (§ 355-26B and C).
• One-family dwellings are also permitted on the same figures.
• Street frontage must be at least 50 ft, which the Planning Board may reduce to 25 ft on a lot at the turnaround of a dead-end street.
• The Planning Board may approve a conservation subdivision with lots of one acre or half the district minimum, whichever is less, and no more lots than a conventional layout would yield.
• On a corner lot the side yard on the side street must equal the required front yard (§ 355-15).
• A one-story accessory building under 800 sq ft, other than a stable, may sit at half the required side or rear distance, but no nearer the street than the front yard.

One-Family Residence District - A new lot needs a contiguous buildable area clear of wetlands, water bodies, floodplains and steep slopes: at least 5,000 sq ft with on-lot septic and a well, 5,000 with septic and central water, 4,500 with central sewer and a well, or 4,000 with central sewer and water.

• Street frontage must be at least 50 ft, which the Planning Board may reduce to 25 ft on a lot at the turnaround of a dead-end street.
• Gross floor area and gross land coverage of a one- or two-family dwelling are capped on a sliding scale by lot size (§ 355-26B and C), and a new lot is measured on net lot area.
• The Planning Board may approve a conservation subdivision with lots of one acre or half the district minimum, whichever is less, and no more lots than a conventional layout would yield.
• On an interstate highway, buildings are set back at least 200 ft from the nearest edge of the mainline pavement.
• A one-story accessory building under 800 sq ft, other than a stable, may sit at half the required side or rear distance, but no nearer the street than the front yard.
• From the lowest grade along an exterior wall, the vertical distance to the roof point where height is measured may not exceed 34 ft (§ 355-26D).

Multifamily-A Residence District - The figures shown are the perimeter requirements for an R-MF-A development site as a whole, with density capped at an average of one density unit per 14,000 sq ft of land area (§ 355-25B(1)). Lots inside the development have their own smaller figures.

• A lot for an attached unit needs at least 25 ft of width, 60 ft of depth and 25 ft of street frontage, with a 10 ft front yard, 10 ft rear and 50% building coverage.
• A lot for a detached unit needs at least 65 ft of width and 60 ft of depth, with a 10 ft front yard, 6 ft side, 10 ft rear and 35% coverage. Accessory structures may sit 3 ft from a side line.
• Detached units may make up to 60% of the dwellings where the approved number of AFFH units is at least doubled (§ 355-25B(3)).
• Half the site must stay permanent open space, every dwelling must connect to public water and sewer, and the AFFH set-aside applies (§ 355-25B).
• A one-family dwelling built as an R-1A use follows the R-1A figures: at least 1 acre, 125 ft of width, 150 ft of depth, a 50 ft front yard, 25 ft side and 40 ft rear.
• For a site of only middle-income units that renovates or expands existing structures, the Planning Board may modify every dimensional requirement (§ 355-25B(5)).

Multifamily-Senior Citizen Housing District - Only the height is fixed. The Town Board sets the lot area, frontage, width, depth, yards, building coverage and dwelling size site by site when it approves the zoning, along with a floor area ratio between 0.15 and 0.4 of net lot area (§ 355-27B(2)).

• The district is mapped site by site, and only on land served by public water and sewer (§ 355-27A and B(1)).
• Each unit has one or two bedrooms, with at least 800 sq ft of floor area for one bedroom and 1,000 sq ft for two (§ 355-27B(3) and (4)).

Residential Multifamily-Single Structure District - Every dwelling unit must be inside the one single structure, and the 0.9 floor area ratio is computed on net lot area (§ 355-28B). Street frontage must be at least 100 ft.

• One AFFH unit is required for every five market-rate units, or one for every 10 where the building received its permanent certificate of occupancy by June 30, 2025 (§ 355-28C).
• A market-rate unit needs at least 600 sq ft for an efficiency, 900 for one bedroom, 1,100 for two, 1,300 for three and 1,500 for four (§ 355-28J).
• Every unit must connect to public water and sewer (§ 355-28D).
• A detached accessory garage needs no side or rear yard where the parcel adjoins public land and the Planning Board finds the location appropriate (§ 355-28I).
• Because the required frontage is less than the lot width, buildings must also observe any special setback lines the Planning Board sets on the subdivision plat.
• A one-family dwelling built as an R-1A use follows the R-1A figures: at least 1 acre, 125 ft of width, 150 ft of depth, a 50 ft front yard, 25 ft side and 40 ft rear.

Designed Office Business 20A District - The Town Board may cut the 20-acre site minimum by up to one third next to New York City watershed land or permanent open space, and by up to two thirds for a density-transfer site.

• Where the approved district is smaller than 20 acres, the height limit drops 1 ft for each 20,000 sq ft below 20 acres.
• A buffer at least 100 ft deep of natural woodland or dense evergreens is required next to a residence lot or a public road (§ 355-30J(3)(d)).
• The 300 ft setback from lot lines other than the street drops to 100 ft along a contiguous nonresidential lot (§ 355-30J(3)(b)).
• A lot needs at least 500 ft of street frontage.
• The Town Board may transfer unused density between OB, OBH and DOB-20A sites, up to a floor area ratio of 0.25 on the receiving site (§ 355-30A(7)).
• The district is mapped site by site by the Town Board (§ 355-30J(1)), and the OB standards apply where they are equal or more restrictive.

Office Business District - Buildings must stand at least 150 ft from the street they front and at least 300 ft from every other lot line, reduced to 100 ft along a contiguous lot in a nonresidential district (§ 355-30A(3)).

• One-story gatehouses, bus shelters and security offices may stand 25 ft from the street.
• Parking must be set back at least 50 ft from all lot boundaries (§ 355-30A(5)).
• Height is measured from the average finished grade along the main front wall (§ 355-30A(4)).
• A lot needs at least 500 ft of street frontage.
• The Town Board may transfer unused density between OB, OBH and DOB-20A sites, up to a floor area ratio of 0.25 on the receiving site (§ 355-30A(7)).
• A side yard giving access to rear parking must be at least 16 ft.

Office Business Hotel - A hotel, the district's permitted principal use, needs at least 3,250 sq ft of lot area for each guest sleeping room, and each room must be at least 225 sq ft (§ 355-30G).

• No structure other than pergolas, canopies, porches, patios, terraces, decks, carports, pools, driveways and parking may stand within 100 ft of a private road or 300 ft of a public park.
• No structure at all may stand within 300 ft of a state road.
• A lot needs at least 500 ft of street frontage.
• The Town Board may transfer unused density between OB, OBH and DOB-20A sites, up to a floor area ratio of 0.25 on the receiving site (§ 355-30A(7)).
• A side yard giving access to rear parking must be at least 16 ft.

Planned Light Industry District - The Planning Board may approve lots of at least 2 acres with at least 200 ft of frontage and depth, in a subdivision whose lots average 4 acres.

• The front yard may drop to 60 ft where no parking lies between the building and the street.
• The side and rear yards may be varied at site plan approval for an existing lot’s size or shape.
• A 10 ft landscaped foundation planting is required along building walls, and two-way driveways must be at least 25 ft wide (§ 355-30D).
• A lot needs at least 300 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft.

Research, Electronic and Light Industrial Park District - The Planning Board may approve lots of at least 2 acres with at least 200 ft of frontage and depth, in a subdivision whose lots average 4 acres.

• A landscaped buffer at least 25 ft deep is required along any lot line abutting a residence district (§ 355-30E).
• Parking must stay at least 25 ft from side and rear lines, and 50 ft where those lines abut a residential district.
• The rear yard may drop to 50 ft where the rear line abuts land dedicated for park use.
• The yards may be varied at site plan approval for an existing lot’s size or shape.
• A lot needs at least 300 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft.

Central Business District - Where the lot abuts a residence district, the side yard must be whatever that residence district requires.

• A dwelling in a business building is allowed only as a separate apartment unit with its own outside entrance meeting all residence requirements (§ 355-29D(2)).
• Such an apartment needs at least 800 sq ft of livable floor area (§ 355-70).
• A lot needs at least 50 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft, and a side line that abuts another lot's rear line needs that lot's rear yard.

Central Business A District - Between 20% and 40% of the district's floor area must be second-story multifamily dwellings, at least 20% of them AFFH units, and a first-floor dwelling needs a Town Board special permit.

• A store or restaurant over 5,000 sq ft needs a Town Board special permit (§ 355-29B(4)).
• No parking is allowed in the front yard unless the Planning Board approves it (§ 355-29B(6)).
• At least 60% of the facade between 2 and 12 ft above grade must be windows and doors (§ 355-29B(7)(j)).
• A lot needs at least 50 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft, and a side line that abuts another lot's rear line needs that lot's rear yard.

Central Business B District - On a state or county road, buildings are set back from the center line of the existing roadway by the required front yard plus 50 ft, which the Planning Board may reduce by up to 20 ft where future widening does not need it (§ 355-29C(2)(a)).

• A side yard is not required, but one that is provided must be at least 6 ft, and at least 25 ft if it is used for vehicle access (§ 355-29C(2)(b)).
• Along a residence district boundary a provided side yard must be at least 50 ft, unless the Planning Board approves less for equivalent screening.
• A dwelling in a business building is allowed only as a separate apartment unit with its own outside entrance meeting all residence requirements (§ 355-29C(3)(b)).
• Such an apartment needs at least 800 sq ft of livable floor area (§ 355-70).
• A lot needs at least 50 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft, and a side line that abuts another lot's rear line needs that lot's rear yard.

General Business District - A one-family dwelling is held to the R-1/2A figures instead: at least 0.5 acre, 125 ft of width, a 40 ft front yard, 20 ft side and 30 ft rear, with 15% building coverage and at least 900 sq ft of livable floor area.

• A dwelling in a business building is allowed only as a separate apartment unit with its own outside entrance meeting all residence requirements (§ 355-29F(2)).
• Such an apartment needs at least 800 sq ft of livable floor area (§ 355-70).
• A lot needs at least 100 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft, and a side line that abuts another lot's rear line needs that lot's rear yard.

Professional Business Office District - Where the lot abuts a residence district, the side yard rises to match whatever that residence district requires.

• No parking may be within 20 ft of a side or rear line that abuts a residence district (§ 355-30C).
• A lot needs at least 100 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft.

Professional Business Office 2A District - Where an existing lot's size or shape warrants it, the Planning Board may vary or reduce the frontage, depth and yards at site plan approval.

• A landscaped buffer at least 25 ft deep is required along any lot line abutting a residence district (§ 355-30B).
• A one-family dwelling follows the R-2A figures, and may not share a lot with another type of use permitted here.
• A lot needs at least 200 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft.

Roadside Business District - An existing lot below the minimum size may still be built on after site plan approval, and a lot less than 200 ft deep takes the depth table of § 355-29E(1)(a), with rear yards from 50 ft down to 10 ft and front yards of 50 to 75 ft by depth.

• The Planning Board may reduce those front yards to fit existing building lines (§ 355-29E(1)(b)).
• Where the lot abuts a residence district, the side yard must be at least what that residence district requires.
• A landscaped strip at least 10 ft deep is required along the front and rear lot lines and where the lot abuts residential property (§ 355-29E(1)(c)).
• A lot needs at least 100 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft, and a side line that abuts another lot's rear line needs that lot's rear yard.

Residence Office District - As an accessory use, residential use is limited to one dwelling unit per building unless a special permit allows more.

• A one-family dwelling follows the R-5 figures, with no floor area ratio and at least 800 sq ft of livable floor area.
• Required parking for nonresidential uses may not be in the front or side yards (§ 355-30I).
• New construction is reviewed for fit with the district's historic buildings under Chapter 195.
• A lot needs at least 50 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft.

Shopping Center District - Where the lot abuts a residence district, the side and rear yards each rise to at least 50 ft.

• In return for community amenities such as road, buffer, wetland or utility improvements, the Town Board may cut the front yard from 75 ft to as little as 30 ft (§ 355-29A(3)).
• The same trade may cut a rear yard abutting a residence district from 50 ft to 22 ft, raise building coverage from 20% to 22% and raise the floor area ratio from 0.25 to 0.27.
• A lot needs at least 300 ft of street frontage, which the Planning Board may reduce to 100 ft on a lot at the turnaround of a dead-end street.
• A side yard giving access to rear parking must be at least 16 ft, and a side line that abuts another lot's rear line needs that lot's rear yard.

Industrial A District - The Planning Board may reduce or eliminate the rear yard where the rear lot line abuts land used for rail transportation.

• A lot needs at least 50 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft.

Industrial AA District - Where an existing lot's size or shape warrants it, the Planning Board may vary or reduce the frontage, depth and yards at site plan approval.

• A lot of at least one acre that existed on April 27, 1961 may be used if it meets the other standards.
• A lot needs at least 200 ft of street frontage.
• A side yard giving access to rear parking must be at least 16 ft.

Nursery Business District - Where the lot abuts a residence district, the side and rear yards must each be at least twice what that residence district requires.

• A lot needs at least 200 ft of street frontage, which the Planning Board may reduce to 100 ft on a lot at the turnaround of a dead-end street.
• R-2A District uses are also permitted here.
• Non-nursery sales and office uses over 5,000 sq ft need a Town Board special use permit.
• A side yard giving access to rear parking must be at least 16 ft, and a side line that abuts another lot's rear line needs that lot's rear yard.