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Rye · ADU cost

What it costs to build an ADU in Rye, NY

800 sq ft ≈ $235k–310k $296–388/sq ft 25 districts Con Edison

An 800 sq ft accessory dwelling unit in Rye runs roughly $235k–310k, or about $296–388/sq ft, and that per-square-foot figure sits deliberately above the $242–318/sq ft a full house costs here. An ADU still needs one whole kitchen, one whole bath, its own service panel and its own heating plant no matter how small you draw it, and those costs do not shrink with the floor plan, so they land on half the square footage and push the rate up. Whether the city will let you build one is a separate question from what it costs, and it gets answered parcel by parcel rather than townwide, since the City of Rye maps 25 districts that treat accessory units differently from one another, so read the table below as a starting point rather than a verdict.

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ADU cost by size in Rye

Standard finish, slab on grade, on a flat and clear part of the lot, general-contractor margin included. These are structure costs at Westchester County pricing, before the service and septic work a second dwelling can trigger.

SizeType$ / sq ftEstimated total
400 sq ft Studio $392–$514 $155k–205k
600 sq ft One bedroom $328–$430 $195k–260k
800 sq ft One bedroom, larger $296–$388 $235k–310k
1,000 sq ft Two bedroom $277–$362 $275k–360k

400 sq ft — One room plus a bath. Garage conversions and small backyard cottages land here.

600 sq ft — The most common detached build - a real bedroom, full kitchen, one bath.

800 sq ft — Room for a proper living area. Still a single bath and one kitchen.

1,000 sq ft — About as large as most codes allow an accessory unit to go.

Why the rate is higher than a house

The systems below are priced for an 800 sq ft unit. The middle column is what each system would cost if it simply shrank with the floor plan; the left column is what it actually costs once you account for the equipment a dwelling needs one of regardless of size. The gap between the two columns is the whole reason small builds price the way they do.

System$ / sq ft in an ADUIf it scaled with floor areaFixed per unit
Site work $9–$13 $9 —
Foundation $19–$27 $19 —
Framing $30–$38 $30 —
Envelope - roof, siding, windows $38–$49 $38 —
Plumbing $33–$40 $19 55%
Electrical $22–$28 $15 35%
HVAC $27–$34 $17 45%
Insulation $9–$11 $9 —
Interior finishes $38–$51 $32 15%
Millwork & cabinetry $22–$33 $13 55%

The fixed-per-unit share is a modeling assumption, not a figure from the code: it is our estimate of how much of each system's budget buys equipment a dwelling needs exactly one of - a kitchen rough-in, a bath group, a service panel, a heating plant - and therefore does not shrink when the unit does. Site work, foundation, framing, envelope and insulation are treated as scaling straight with floor area, which understates the premium slightly, because a small building carries more envelope per square foot of floor than a large one.

What the Rye code says about accessory units

Whether you can build one, and how large, is decided by the district your parcel sits in rather than by the town as a whole. The table shows how each mapped district treats ADUs alongside the lot and setback standards a second unit still has to fit inside. District boundaries and conditions vary, so treat it as a starting point and confirm the district that applies to your parcel.

District Min lot Setbacks F / S / R Max height ADU
One-Family District 1 ac 35 / 20 / 60 ft 32 ft Occupancy restricted
One-Family District 0.5 ac 35 / 15 / 50 ft 32 ft Occupancy restricted
Residential Floodplain and Wetland Preservation District 10 ac 85 / - / - ft 35 ft —
One-Family District 0.33 ac 30 / 12 / 40 ft 28 ft Occupancy restricted
One-Family District 0.23 ac 30 / 10 / 30 ft 28 ft Occupancy restricted
One-Family District 0.16 ac 30 / 8 / 30 ft 28 ft Occupancy restricted
One-Family District 0.14 ac 25 / 8 / 25 ft 28 ft Occupancy restricted
Garden Apartment District 0.11 ac 25 / 8 / 30 ft 35 ft Occupancy restricted
School and Church District 0.5 ac 30 / 12 / 40 ft 28 ft Occupancy restricted
Apartment District 0.11 ac 25 / 8 / 30 ft 35 ft Occupancy restricted
Two-Family District 0.11 ac 25 / 8 / 30 ft 28 ft Occupancy restricted
Apartment District 0.11 ac 25 / 8 / 30 ft 35 ft Occupancy restricted
Apartment District 0.11 ac 25 / 8 / 30 ft 35 ft Occupancy restricted
Senior Citizens Apartment District 1 ac 25 / - / - ft 50 ft Occupancy restricted
Office Building District 0.5 ac 35 / 15 / 50 ft 35 ft No
Interchange Office Building District 0.5 ac 35 / 15 / 50 ft 35 ft No
Neighborhood Business District 0.11 ac 25 / 8 / 30 ft 35 ft No
Central Business District — - / 0 / - ft 35 ft No
Beach Business District 0.11 ac 25 / 8 / 30 ft 35 ft No
General Business District — - / 0 / - ft 40 ft No
Waterfront Business District — 5 / 0 / - ft 35 ft No
Conservation District — — 35 ft No
Membership Club District 7.5 ac — 35 ft No
Waterfront Recreation District 7.5 ac — 35 ft No
Active Senior Residence District — 150 / 50 / 50 ft 45 ft —

One-Family District - On a lot larger than 150% of the district minimum, the floor area ratio is cut to one half on the part between 150% and 250% of the minimum and to one quarter beyond 250% (§ 197-43.1).

  • A one-story accessory structure needs at least 20 ft from the side line and may cover at most 20% of the required rear yard.
  • For a lot created after January 1, 2022, no part of the lot between the street line and the required rear yard may be narrower than 75 ft (§ 197-36A).
  • A subdivision of 3 acres or more may group lots to meet the single-family figures of the next less restrictive district, with at least 30% open space and no more lots than a conventional layout.
  • Where a required yard abuts a street less than 50 ft wide, it is measured from a line 25 ft from the street center line.
  • No building may be nearer than 100 ft to the center line of the Post Road between the Mamaroneck line and Central Avenue.
  • A single-family house, and each unit of a two-family house, needs at least 1,000 sq ft of residential floor area (§ 197-44A).

One-Family District - On a lot larger than 150% of the district minimum, the floor area ratio is cut to one half on the part between 150% and 250% of the minimum and to one quarter beyond 250% (§ 197-43.1).

  • A senior living facility for residents 55 and over, by special permit, needs at least 50 contiguous acres, a 0.43 floor area ratio, 15% building and 33% impervious coverage and at least 160 ft yards.
  • Its yards rise to at least 300 ft from Osborn Road, reducible to 100 ft beside uses other than single-family houses, RA-5 senior apartments or a school.
  • That facility may rise to 4 stories or 55 ft, or 5 stories and 65 ft where the building stands at least 240 ft from every property line, and must keep 60% open space.
  • A one-story accessory structure needs at least 15 ft from the side line and may cover at most 20% of the required rear yard.
  • For a lot created after January 1, 2022, no part of the lot between the street line and the required rear yard may be narrower than 75 ft (§ 197-36A).
  • A subdivision of 3 acres or more may group lots to meet the single-family figures of the next less restrictive district, with at least 30% open space and no more lots than a conventional layout.

Residential Floodplain and Wetland Preservation District - The setback from every property line other than a street depends on the prior zoning: on former R-1 land 60 ft for a single-family house, 70 ft for a two-family and 85 ft for apartments, and on former R-2 land 50, 60 and 75 ft.

  • Every building must stand at least 85 ft from all street frontages.
  • Building coverage may not exceed 2,600 sq ft per approved dwelling unit on former R-1 land or 1,700 sq ft on former R-2 land, and total floor area may not exceed 2.5 times that coverage.
  • No building may hold more than four units or exceed 120 ft in length, and buildings must be at least 25 ft apart.
  • Each unit needs its own ground-level entrance, and the lowest floor must be at least 2 ft above base flood elevation.
  • The district is mapped by rezoning an R-1 or R-2 lot of at least 10 acres under single ownership, at least 25% of it wetland or special flood hazard area.
  • The unit count follows the § 197-13.1B(3) formula, or at the applicant's option one unit per buildable lot of a conventional single-family layout under the prior zoning.

One-Family District - In a special flood hazard area a lot needs at least 1/2 acre, against at least 1/3 acre elsewhere; the yards are the same in and out of the flood area.

  • On a lot larger than 150% of the district minimum, the floor area ratio is cut to one half on the part between 150% and 250% of the minimum and to one quarter beyond 250% (§ 197-43.1).
  • A one-story accessory structure needs at least 10 ft from the side line and may cover at most 35% of the required rear yard.
  • Lots 90% or more outside the flood area, or in subdivisions tentatively approved before February 17, 1988, take the other-areas figure (§ 197-37.1).
  • For a lot created after January 1, 2022, no part of the lot between the street line and the required rear yard may be narrower than 75 ft (§ 197-36A).
  • A subdivision of 3 acres or more may group lots to meet the single-family figures of the next less restrictive district, with at least 30% open space and no more lots than a conventional layout.
  • No building may be nearer than 100 ft to the center line of the Post Road between the Mamaroneck line and Central Avenue.

One-Family District - In a special flood hazard area a lot needs at least 1/2 acre, against at least 10,000 sq ft elsewhere; the yards are the same in and out of the flood area.

  • On a lot larger than 150% of the district minimum, the floor area ratio is cut to one half on the part between 150% and 250% of the minimum and to one quarter beyond 250% (§ 197-43.1).
  • A one-story accessory structure needs at least 10 ft from the side line and may cover at most 25% of the required rear yard.
  • Lots 90% or more outside the flood area, or in subdivisions tentatively approved before February 17, 1988, take the other-areas figure (§ 197-37.1).
  • For a lot created after January 1, 2022, no part of the lot between the street line and the required rear yard may be narrower than 75 ft (§ 197-36A).
  • A subdivision of 3 acres or more may group lots to meet the single-family figures of the next less restrictive district, with at least 30% open space and no more lots than a conventional layout.
  • No building may be nearer than 100 ft to the center line of the Post Road between the Mamaroneck line and Central Avenue.

One-Family District - In a special flood hazard area a lot needs at least 1/2 acre, against at least 7,000 sq ft elsewhere; the yards are the same in and out of the flood area.

  • On a lot larger than 150% of the district minimum, the floor area ratio is cut to one half on the part between 150% and 250% of the minimum and to one quarter beyond 250% (§ 197-43.1).
  • A one-story accessory structure needs at least 5 ft from the side line and may cover at most 30% of the required rear yard.
  • § 197-2 describes the district with a minimum of 7,500 sq ft outside the flood hazard area, against the 7,000 sq ft the district schedule sets.
  • Lots 90% or more outside the flood area, or in subdivisions tentatively approved before February 17, 1988, take the other-areas figure (§ 197-37.1).
  • For a lot created after January 1, 2022, no part of the lot between the street line and the required rear yard may be narrower than 75 ft (§ 197-36A).
  • A subdivision of 3 acres or more may group lots to meet the single-family figures of the next less restrictive district, with at least 30% open space and no more lots than a conventional layout.

One-Family District - In a special flood hazard area a lot needs at least 1/2 acre, against at least 6,000 sq ft elsewhere; the yards are the same in and out of the flood area.

  • On a lot larger than 150% of the district minimum, the floor area ratio is cut to one half on the part between 150% and 250% of the minimum and to one quarter beyond 250% (§ 197-43.1).
  • A one-story accessory structure needs at least 5 ft from the side line and may cover at most 30% of the required rear yard.
  • Lots 90% or more outside the flood area, or in subdivisions tentatively approved before February 17, 1988, take the other-areas figure (§ 197-37.1).
  • For a lot created after January 1, 2022, no part of the lot between the street line and the required rear yard may be narrower than 75 ft (§ 197-36A).
  • A subdivision of 3 acres or more may group lots to meet the single-family figures of the next less restrictive district, with at least 30% open space and no more lots than a conventional layout.
  • No building may be nearer than 100 ft to the center line of the Post Road between the Mamaroneck line and Central Avenue.

Garden Apartment District - The figures shown are for a single-family house; a two-family house owes the same yards on a lot at least 60 ft wide. An apartment house needs at least 70 ft front, 50 ft on one side, 100 ft on both sides combined and 50 ft rear, on a lot at least 100 ft wide.

  • Every house or apartment needs at least 5,000 sq ft of lot for each family.
  • An apartment house needs a site plan approved by the Planning Commission, at least 400 sq ft of outdoor recreation space per family and an average of at least 750 sq ft of floor area per unit.
  • Where all habitable rooms of an apartment face one side yard, that side yard must equal the required rear yard (§ 197-54).
  • Moderate-income housing on lots fronting Cottage Street or Theodore Fremd Avenue, by special permit, uses a 1.0 floor area ratio and at least 2,500 sq ft of lot per family.
  • One-story accessory structures may cover at most 30% of the required rear yard and need at least 5 ft from the side line, 10 ft for an apartment house.
  • No building may be nearer than 100 ft to the center line of the Post Road between the Mamaroneck line and Central Avenue.

School and Church District - The figures shown are for a single-family house. Any other permitted use needs at least 50 ft front, a side yard of half the building height but at least 12 ft, at least 40 ft on both sides combined and 40 ft rear, on at least 1/3 acre.

  • Any other permitted use, such as a school or place of worship, needs Planning Commission findings after a public hearing and may rise to 35 ft.
  • For that use, one-story accessory structures may cover at most 10% of the required rear yard and need at least 12 ft from the side line.
  • For a house, a one-story accessory structure needs at least 10 ft from the side line and may cover at most 25% of the required rear yard.
  • Where a required yard abuts a street less than 50 ft wide, it is measured from a line 25 ft from the street center line.
  • A single-family house, and each unit of a two-family house, needs at least 1,000 sq ft of residential floor area (§ 197-44A).

Apartment District - The figures shown are for a single-family house. A two-family house owes the same yards on a lot at least 60 ft wide, with at least 3,500 sq ft per family.

  • An apartment house needs at least 25 ft front, 20 ft on one side, 50 ft on both sides combined and 40 ft rear, on a lot at least 100 ft wide.
  • An apartment house needs at least 3,500 sq ft of lot per family, at least 200 sq ft of outdoor recreation space per family and an average of at least 750 sq ft of floor area per unit.
  • A single-family house needs at least 5,000 sq ft of lot per family.
  • Where all habitable rooms of an apartment face one side yard, that side yard must equal the required rear yard (§ 197-54).
  • One-story accessory structures may cover at most 30% of the required rear yard and need at least 5 ft from the side line, 10 ft for an apartment house.
  • No building may be nearer than 100 ft to the center line of the Post Road between the Mamaroneck line and Central Avenue.

Two-Family District - The figures shown are for a single-family house. A two-family house owes the same yards on a lot at least 60 ft wide, with at least 3,000 sq ft per family.

  • A single-family house needs at least 5,000 sq ft of lot per family.
  • A one-story accessory structure needs at least 5 ft from the side line and may cover at most 30% of the required rear yard.
  • Where a required yard abuts a street less than 50 ft wide, it is measured from a line 25 ft from the street center line.
  • No building may be nearer than 100 ft to the center line of the Post Road between the Mamaroneck line and Central Avenue.
  • A single-family house, and each unit of a two-family house, needs at least 1,000 sq ft of residential floor area (§ 197-44A).

Apartment District - The figures shown are for a single-family house. A two-family house owes the same yards on a lot at least 60 ft wide, with at least 3,000 sq ft per family.

  • An apartment house needs at least 25 ft front, 20 ft on one side, 40 ft on both sides combined and 40 ft rear, on a lot at least 80 ft wide, and may rise to 40 ft.
  • An apartment house needs at least 2,500 sq ft of lot per family, at least 200 sq ft of outdoor recreation space per family and an average of at least 750 sq ft of floor area per unit.
  • A single-family house needs at least 5,000 sq ft of lot per family.
  • Where all habitable rooms of an apartment face one side yard, that side yard must equal the required rear yard (§ 197-54).
  • One-story accessory structures may cover at most 35% of the required rear yard and need at least 5 ft from the side line, 10 ft for an apartment house.
  • No building may be nearer than 100 ft to the center line of the Post Road between the Mamaroneck line and Central Avenue.

Apartment District - The figures shown are for a single-family house. A two-family house owes the same yards on a lot at least 60 ft wide, with at least 3,000 sq ft per family.

  • An apartment house needs at least 25 ft front, 20 ft on one side, 40 ft on both sides combined and 40 ft rear, on a lot at least 80 ft wide.
  • An apartment house needs at least 2,500 sq ft of lot per family, at least 200 sq ft of outdoor recreation space per family and an average of at least 750 sq ft of floor area per unit.
  • A variable-height apartment group, by special permit, may rise to 45 ft or 4 stories with an average height of 30 ft (§ 197-13).
  • Any building in that group over 30 ft must stand at least 1 1/2 times its height from every lot line.
  • An apartment side yard holding a driveway that serves more than six parking spaces must be at least 25 ft.
  • The Board of Appeals may cut the side yard to 8 ft when a house existing on August 9, 1956 is converted to up to four families.

Senior Citizens Apartment District - The district is for apartments for senior citizens and handicapped persons, undertaken by nonprofit sponsors with public financial assistance, and needs at least 800 sq ft of lot for each family.

  • Where all habitable rooms of a unit face one side yard, that side yard must be at least 30 ft (§ 197-54).
  • Every unit needs at least 400 sq ft of floor area, and the site needs at least 40 sq ft of outdoor recreation space per family.
  • One-story accessory structures may cover at most 35% of the required rear yard and need at least 10 ft from the side line.
  • Where a required yard abuts a street less than 50 ft wide, it is measured from a line 25 ft from the street center line.
  • No building may be nearer than 100 ft to the center line of the Post Road between the Mamaroneck line and Central Avenue.

Office Building District - An office building, the district's main use, needs Planning Commission findings after a public hearing and an approved site development plan, on at least 7 acres plus one acre for each 30 employees, or fraction, beyond 300.

  • That office building needs at least 400 ft of width, a 100 ft front yard, 100 ft one side, 200 ft both sides and 100 ft rear, and stands at most 3 stories or 45 ft, covering at most 15% of the lot.
  • The figures shown are for nonresidential uses permitted in R-2 Districts.
  • Office parking must be screened and set back at least 50 ft from street, side and rear lot lines (§ 197-11B).
  • The Planning Commission may reduce or waive yards beside a railroad or limited access highway, or reduce side and rear yards to 25 ft beside B-5 or B-6 land.
  • A lot abutting a residence district takes that district's side and rear yards and a 10 ft landscaped strip (§ 197-69).
  • For those nonresidential uses permitted in R-2 Districts, one-story accessory structures need at least 15 ft from the side line and may cover at most 20% of the required rear yard.

Interchange Office Building District - An office building, the district's main use, needs Planning Commission findings after a public hearing and an approved site development plan: at least 3 acres, 300 ft of width, a 100 ft front yard, 50 ft one side, 125 ft both sides and 75 ft rear.

  • That office building may cover at most 35% of the site with buildings and structures and 65% with all impervious surfaces, at a 0.5 floor area ratio and 3 stories or 44 ft.
  • A hotel needs a 0.45 floor area ratio and at least 3,000 sq ft of lot per rental sleeping room, 1,400 sq ft for a four-story hotel with full elevator service.
  • A hotel's front yard rises to 125 ft from a county road that is not limited access, and it may rise to 4 stories or 65 ft.
  • The figures shown are for nonresidential uses permitted in R-2 Districts.
  • Within 100 ft of a street line facing a residence district, no building may exceed 120 ft in horizontal dimension or stand within 60 ft of another such building (§ 197-12B).
  • A lot abutting a residence district takes that district's side and rear yards and a 10 ft landscaped strip (§ 197-69).

Neighborhood Business District - The figures shown are for a single-family house. For all other main buildings, including a second-floor dwelling over a nonresidential use, the rear yard must be at least the building height except within 60 ft of a street, and no side yard is required.

  • Apartment houses are allowed only on lots fronting Boston Post Road between Purchase Street and Purdy Avenue, by special permit, at a 1.0 floor area ratio with at least 80 ft of width.
  • A two-family house needs at least 8,000 sq ft of lot for each family and at least 60 ft of width, with the same yards.
  • No rear yard is required against a municipal parking lot.
  • A lot facing or abutting a residence district takes that district's side and rear yards, a 10 ft landscaped strip, and a landscaped front yard at least 10 ft deep where it faces one across a street.
  • No building may be nearer than 100 ft to the Boston Post Road center line between the Mamaroneck village line and Central Avenue.
  • A single-family house, and each unit of a two-family house, needs at least 1,000 sq ft of residential floor area (§ 197-44A).

Central Business District - The rear yard must be at least the building height except within 60 ft of a street, and no side yard is required (§ 197-55). Dwelling units may not be on the first floor, except in an existing building with first-floor units on Purchase Street.

  • A dwelling unit must average at least 500 sq ft of floor area (§ 197-44C).
  • A hotel needs at least 2,500 sq ft of lot for each two guest sleeping rooms, with a 20 ft front yard, 15 ft one side, 40 ft both sides and 40 ft rear.
  • A lodging house needs at least 5,000 sq ft of lot for each two guest sleeping rooms, with a 20 ft front yard, 8 ft one side, 20 ft both sides and 30 ft rear.
  • No rear yard is required against a municipal parking lot.
  • A lot facing or abutting a residence district takes that district's side and rear yards, a 10 ft landscaped strip, and a landscaped front yard at least 10 ft deep where it faces one across a street.
  • Offices may not occupy the first floor within the A Parking District.

Beach Business District - The figures shown are for a single-family house. All other main buildings owe a 25 ft front yard, at least 12 ft on one side, 24 ft on both sides combined and 40 ft rear.

  • A two-family house needs at least 3,000 sq ft of lot for each family and at least 60 ft of width, with the same yards.
  • Apartments need Planning Commission findings after a public hearing, a lot of at least 6 acres and the RA-2 apartment house figures.
  • For those apartments a one-bedroom unit needs at least 3,000 sq ft of lot and a unit of three or more bedrooms at least 4,000 sq ft, at 35% total coverage.
  • One-story accessory structures for other main buildings need at least 10 ft from the side line.
  • A lot abutting a residence district takes that district's side and rear yards and a 10 ft landscaped strip (§ 197-69).
  • A single-family house, and each unit of a two-family house, needs at least 1,000 sq ft of residential floor area (§ 197-44A).

General Business District - The rear yard must be at least the building height except within 60 ft of a street, and no side yard is required (§ 197-55).

  • No rear yard is required against a municipal parking lot.
  • A lot facing or abutting a residence district takes that district's side and rear yards, a 10 ft landscaped strip, and a landscaped front yard at least 10 ft deep where it faces one across a street.

Waterfront Business District - The district's main uses, small boat facilities, marine hardware, fuel and supply sales and services, and public and private recreation, all need Planning Commission findings after a public hearing (§ 197-10).

  • The rear yard must be at least the building height except within 60 ft of a street, and no side yard is required (§ 197-55).
  • No rear yard is required against a municipal parking lot.
  • A lot facing or abutting a residence district takes that district's side and rear yards and a 10 ft landscaped strip, with a landscaped front yard where it faces one across a street.

Conservation District - The Conservation District is for nature preserves: buildings, structures and man-made surfaces may not exceed 1/2 of 1% of the site's area or cover more than 10% of it.

  • Accessory structures may rise 1 story or 12 ft.

Membership Club District - A membership club needs a lot of at least 7.5 acres, and all club parcels in common ownership, contiguous or separated by a road, count as one parcel toward it. No club building, parking lot or recreational use may be within 100 ft of any lot line.

  • Half of the site must stay natural ground cover.
  • A single-family house, by special permit, uses the R-1 figures: at least 1 acre, 150 ft of width, a 35 ft front yard, 20 ft one side, 50 ft both sides and 60 ft rear.
  • Lots subdivided after June 28, 1991 must be lot grouped at the R-3 standard with at least half the land kept as open space.
  • Club buildings and development existing on June 28, 1991 that do not meet current setbacks are not nonconforming (§ 197-5A(10)).
  • Residential accessory structures may rise 1 1/2 stories or 15 ft.

Waterfront Recreation District - Private recreation needs a lot of at least 7.5 acres, and half the site must remain natural ground cover.

  • No building, parking area or grounds for picnicking or organized games may be within 100 ft of any lot line, and no green or fairway within it.
  • Public recreation uses have no lot minimum or floor area ratio.
  • Residential accessory structures may rise 2 stories or 30 ft with public recreation and 1 1/2 stories or 15 ft with private recreation.

Active Senior Residence District - Occupancy is limited to households aged 55 and over (§ 197-8.1A), and a site plan approved by the Planning Commission is required (§ 197-7).

  • The 150 ft front yard may be reduced to 100 ft where the building covers less than 15% of the area between the reduced line and the 150 ft line.
  • On a corner lot the Boston Post Road or Old Post Road frontage is the front (§ 197-8.1B(2)).
  • A landscaped buffer at least 10 ft wide must run around the site (§ 197-8.1B(4)).
  • Each unit needs at least 750 sq ft of floor area for one bedroom, 900 sq ft for two and 1,100 sq ft for three (§ 197-44E).
  • § 197-2 describes the district at 2,000 sq ft of lot per family, against the 2,500 sq ft the district schedule sets.
  • One-story accessory structures may cover at most 35% of the required rear yard and need at least 10 ft from the side line.
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Costs an ADU adds that a house does not

Sizing up a specific parcel in Rye?

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Building a full house instead?

A standard-finish house in Rye runs $242–318/sq ft, about $435k–570k at 1,800 sq ft . See what it costs to build a house in Rye.

ADU cost in nearby towns

Mount Vernon (City)
800 sq ft ≈ $235k–310k
New Rochelle (City)
800 sq ft ≈ $235k–310k
Peekskill (City)
800 sq ft ≈ $235k–310k
White Plains (City)
800 sq ft ≈ $235k–310k
Yonkers (City)
800 sq ft ≈ $235k–310k
Bedford
800 sq ft ≈ $235k–310k

All Westchester County towns: Mount Vernon (City) · New Rochelle (City) · Peekskill (City) · White Plains (City) · Yonkers (City) · Bedford · Cortlandt · Eastchester · Greenburgh · Lewisboro · Mamaroneck · Mount Pleasant · New Castle · North Castle · North Salem · Ossining · Pound Ridge · Somers · Yorktown · Harrison (Village) · Ardsley (Village) · Briarcliff Manor (Village) · Bronxville (Village) · Buchanan (Village) · Croton-on-Hudson (Village) · Dobbs Ferry (Village) · Elmsford (Village) · Hastings-on-Hudson (Village) · Irvington (Village) · Larchmont (Village) · Mamaroneck (Village) · Mount Kisco (Village) · Ossining (Village) · Pelham (Village) · Pelham Manor (Village) · Pleasantville (Village) · Port Chester (Village) · Rye Brook (Village) · Scarsdale (Village) · Sleepy Hollow (Village) · Tarrytown (Village) · Tuckahoe (Village)

More on Rye: Can you build an ADU here? · Zoning for new construction · Westchester County build cost

ADU cost in Rye: common questions

How much does it cost to build an ADU in Rye, NY?

An 800 sq ft accessory dwelling unit in City of Rye runs roughly $235k–310k at a standard finish, general-contractor margin included. A 400 sq ft studio runs about $155k–205k. Those are structure costs on an easy site and do not include the septic, water or electrical service work a second unit often triggers.

Why does an ADU cost more per square foot than a house in Rye?

Because a lot of a dwelling's cost is per dwelling, not per square foot. One kitchen, one bath group, one service panel and one heating plant cost about the same in an 800 sq ft cottage as in a 1,800 sq ft house, so on the smaller unit they get spread over less than half the floor area. That is why an ADU here prices at $296–388/sq ft against $242–318/sq ft for a full house, even though it is the same trades doing the same work.

Are ADUs allowed in Rye?

City of Rye has 25 districts. 13 districts allow ADUs with occupancy restrictions, 10 do not. 2 districts have incomplete data - verify with the building department at (914) 967-7372. Check the specific address with the free ADU checker before you spend money on design.

Can I rent an ADU in Rye short term?

No local short-term-rental law on record - which is not the same as permission for City of Rye. ADU rules and short-term-rental rules are set separately, so a unit you are allowed to build is not automatically one you are allowed to rent nightly. Confirm both before you underwrite the build on short-term-rental income.

ADU costs are modeled estimates in current 2026 dollars at the Westchester County regional index, general-contractor margin included, derived from Offsite's cost engine with a stated adjustment for the equipment a dwelling needs one of regardless of size. They are planning numbers for decision-support only - not a bid, quote, or guarantee, and not legal, architectural or engineering advice. They cover the structure and exclude septic expansion, utility service runs, site work beyond a flat and clear pad, and permit fees. ADU eligibility, size, owner-occupancy and permit conditions in the City of Rye vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-09-21; verify with the building department at (914) 967-7372 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.

Building outside these counties?

Aldo covers 15 New York counties today. Tell us your market and we'll build the zoning + feasibility data for it.