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Ossining · ADU cost

What it costs to build an ADU in Ossining, NY

800 sq ft ≈ $235k–310k $296–388/sq ft 23 districts Con Edison

An 800 sq ft accessory dwelling unit in Ossining 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 village 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 Village of Ossining maps 23 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 Ossining

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 Ossining 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
Conservation Development District 2 ac 30 / 30 / 30 ft 48 ft No
Planned Residence District — 20 / 20 / 40 ft 35 ft No
Single-Family Residence District 0.23 ac 30 / 20 / 40 ft 35 ft No
Single-Family Residence District 0.34 ac 45 / 30 / 45 ft 35 ft No
Single-Family Residence District 0.11 ac 30 / 8 / 30 ft 35 ft No
Single-Family Residence District 0.17 ac 30 / 8 / 30 ft 35 ft No
Two-Family Residence District 0.17 ac 30 / 8 / 30 ft 35 ft No
Multifamily Residence District 0.92 ac 40 / 30 / 35 ft 35 ft No
Riverfront Development District 0.92 ac — 36 ft No
Institutional/Redevelopment District 5 ac 30 / 30 / 30 ft 48 ft No
Multifamily Residence District 0.92 ac 40 / 30 / 25 ft 70 ft No
Northern Waterfront Subdistrict 0.92 ac 20 / 15 / 15 ft 72 ft No
Central Waterfront - Transit-Oriented Subdistrict 0.92 ac 20 / 15 / 15 ft 48 ft No
Central Waterfront - Hillside Subdistrict 0.23 ac 15 / 10 / 20 ft 48 ft No
Office-Research District 2 ac 50 / 50 / 100 ft 36 ft No
General Business District — 15 / 10 / 20 ft 36 ft No
Neighborhood Center District — 10 / 10 / 20 ft 36 ft No
Neighborhood Center District — - / 10 / 20 ft 36 ft No
Professional Office District 0.23 ac 25 / 10 / 20 ft 35 ft No
Planned Center District 2 ac 20 / 20 / 20 ft 36 ft No
Station Plaza South District 1 ac 15 / 15 / 15 ft 24 ft No
Station Plaza North District — — 48 ft No
Village Center District — — 48 ft No

Conservation Development District - No building, parking area or loading area may stand within 30 ft of any street or lot line.

  • Dwelling units are a conditional use here, not a use of right, at six dwelling units per acre, which the Planning Board may raise to eight in exchange for amenities.
  • A lot abutting a residential district needs a buffer of at least 25 ft, and every buffer must be screened.
  • At least 25% of the lot area must be open space, and buildings must stand at least 35 ft apart.
  • Wetlands are deducted in full from developable land before coverage, lot area and density are worked out, § 270-19.
  • A riverfront setback of at least 50 ft applies under § 270-22.
  • A studio or efficiency apartment must be at least 600 sq ft, a one-bedroom 750 and a two-bedroom 900, with another 350 sq ft for each additional bedroom.

Planned Residence District - The figures shown are for detached housing. A lot abutting a residential district also owes a buffer of at least 10 ft for detached or two-family housing, or at least 20 ft for attached.

  • The development as a whole must cover at least 3 acres undivided by an existing public street, § 270-12H.
  • Attached housing comes only with a Planning Board density bonus, and needs a lot at least 200 ft wide and a front yard of at least 40 ft.
  • Parking and loading for attached housing must sit at least 40 ft from any street or lot line.
  • Density runs to six dwelling units per acre for detached and two-family housing, and the bonus can carry attached housing to eight.
  • No building other than a small accessory building may stand closer to another building than the height of the taller one, and never closer than 30 ft, § 270-12H.
  • A dwelling unit needs at least 750 sq ft of livable floor area in two-family housing and at least 600 sq ft in attached housing.

Single-Family Residence District - On a lot wider than the district minimum, the two side yards must together equal 40% of the lot width, and each side yard must be at least 45% of that total.

  • A flag lot needs 40 ft of frontage on a street and requires site plan approval as well as subdivision approval, § 270-27D.
  • On a corner lot a front yard is required on both street frontages, and on a through lot on every street line, § 270-27C.
  • An accessory building may stand in a required side or rear yard if it is no taller than 15 ft and at least 5 ft from any lot line, with a cap of 750 sq ft in the aggregate and 30% of that yard.
  • Cluster development lets the Planning Board reduce lot area, lot width and the yards, but not height, floor area ratio or development coverage, and net density stays at six dwelling units per acre.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-27H.
  • An applicant for a residential use must provide affordable housing under Chapter 62.

Single-Family Residence District - On a lot wider than the district minimum, the two side yards must together equal 40% of the lot width, and each side yard must be at least 45% of that total.

  • A flag lot needs 50 ft of frontage on a street and requires site plan approval as well as subdivision approval, § 270-27D.
  • On a corner lot a front yard is required on both street frontages, and on a through lot on every street line, § 270-27C.
  • An accessory building may stand in a required side or rear yard if it is no taller than 15 ft and at least 5 ft from any lot line, with a cap of 750 sq ft in the aggregate and 30% of that yard.
  • Cluster development lets the Planning Board reduce lot area, lot width and the yards, but not height, floor area ratio or development coverage, and net density stays at six dwelling units per acre.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-27H.
  • An applicant for a residential use must provide affordable housing under Chapter 62.

Single-Family Residence District - On a lot wider than the district minimum, the two side yards must together equal 40% of the lot width, and each side yard must be at least 45% of that total.

  • A flag lot needs 20 ft of frontage on a street and requires site plan approval as well as subdivision approval, § 270-27D.
  • On a corner lot a front yard is required on both street frontages, and on a through lot on every street line, § 270-27C.
  • An accessory building may stand in a required side or rear yard if it is no taller than 15 ft and at least 5 ft from any lot line, with a cap of 750 sq ft in the aggregate and 30% of that yard.
  • Cluster development lets the Planning Board reduce lot area, lot width and the yards, but not height, floor area ratio or development coverage, and net density stays at six dwelling units per acre.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-27H.
  • An applicant for a residential use must provide affordable housing under Chapter 62.

Single-Family Residence District - On a lot wider than the district minimum, the two side yards must together equal 40% of the lot width, and each side yard must be at least 45% of that total.

  • A flag lot needs 30 ft of frontage on a street and requires site plan approval as well as subdivision approval, § 270-27D.
  • On a corner lot a front yard is required on both street frontages, and on a through lot on every street line, § 270-27C.
  • An accessory building may stand in a required side or rear yard if it is no taller than 15 ft and at least 5 ft from any lot line, with a cap of 750 sq ft in the aggregate and 30% of that yard.
  • Cluster development lets the Planning Board reduce lot area, lot width and the yards, but not height, floor area ratio or development coverage, and net density stays at six dwelling units per acre.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-27H.
  • An applicant for a residential use must provide affordable housing under Chapter 62.

Two-Family Residence District - On a lot wider than the district minimum, the two side yards must together equal 40% of the lot width, and each side yard must be at least 45% of that total.

  • A moratorium added in November 2025 suspends the processing and approval of conditional use permits in this district; confirm with the building department whether it is still in force.
  • On a corner lot a front yard is required on both street frontages, and on a through lot on every street line, § 270-27C.
  • An accessory building may stand in a required side or rear yard if it is no taller than 15 ft and at least 5 ft from any lot line, with a cap of 750 sq ft in the aggregate and 30% of that yard.
  • Cluster development lets the Planning Board reduce lot area, lot width and the yards, but not height, floor area ratio or development coverage, and net density stays at six dwelling units per acre.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-27H.
  • An applicant for a residential use must provide affordable housing under Chapter 62.

Multifamily Residence District - Land per dwelling unit runs by bedroom count: at least 3,600 sq ft for a one-bedroom unit, 4,000 for a two-bedroom, 4,200 for a three-bedroom and 4,500 for four or more bedrooms.

  • Common open space runs the same way, 200 sq ft for a one-bedroom unit, 300 for a two-bedroom, 400 for a three-bedroom and 600 for four or more bedrooms.
  • At least 25% of the required common open space must be equipped, landscaped active recreation.
  • Principal buildings must stand apart by 1.5 times the height of the taller of them or 25 ft, whichever is more, and no building may be longer than 160 ft, § 270-11E.
  • A studio or efficiency apartment must be at least 600 sq ft, a one-bedroom 750 and a two-bedroom 900, with another 350 sq ft for each additional bedroom.
  • On a lot wider than the district minimum, the two side yards must together equal 40% of the lot width, and each must be at least 45% of that total.
  • An applicant for a residential use must provide affordable housing under Chapter 62.

Riverfront Development District - A riverfront setback of at least 50 ft applies under § 270-22, and the setback from Westerly Road may be no more than 15 ft.

  • Residential dwelling units are not permitted here, and a moratorium adopted in July 2025 suspends the processing and approval of applications to build them; confirm with the building department.
  • Parking and loading areas must sit at least 10 ft from any side lot line.
  • Buildings must stand at least 40 ft apart, and at least 15% of the lot area must be open space.
  • On the Westerly Road frontage pedestrian entrances may be no more than 70 ft apart.
  • A special permit under § 270-22 can overlay a qualifying riverfront site near the railroad station with a floor area ratio of 1.5, up to 48 dwelling units per acre and 80 ft of height.

Institutional/Redevelopment District - No building, parking area or loading area may stand within 30 ft of any street or lot line, and a riverfront setback of at least 50 ft applies under § 270-24.

  • Dwelling units are a conditional use here, not a use of right, at 15 dwelling units per acre, which the Planning Board may raise to 20 in exchange for amenities.
  • East of the railroad tracks no building may rise more than 1 story or 16 ft above the westerly curb line of State Street.
  • A lot abutting a residential district needs a buffer of at least 25 ft, and every buffer must be screened.
  • Buildings must stand at least 50 ft apart, and at least 30% of the lot area must be open space.
  • A studio or efficiency apartment must be at least 600 sq ft, a one-bedroom 750 and a two-bedroom 900, with another 350 sq ft for each additional bedroom.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-28F.

Multifamily Residence District - Land per dwelling unit runs by bedroom count: at least 1,000 sq ft for a one-bedroom unit, 1,500 for a two-bedroom, 3,000 for a three-bedroom and 3,600 for four or more bedrooms.

  • Common open space runs the same way, 200 sq ft for a one-bedroom unit, 300 for a two-bedroom, 400 for a three-bedroom and 600 for four or more bedrooms.
  • At least 25% of the required common open space must be equipped, landscaped active recreation.
  • Principal buildings must stand apart by 1.5 times the height of the taller of them or 25 ft, whichever is more, and no building may be longer than 160 ft, § 270-11E.
  • A studio or efficiency apartment must be at least 600 sq ft, a one-bedroom 750 and a two-bedroom 900, with another 350 sq ft for each additional bedroom.
  • On a lot wider than the district minimum, the two side yards must together equal 40% of the lot width, and each must be at least 45% of that total.
  • An applicant for a residential use must provide affordable housing under Chapter 62.

Northern Waterfront Subdistrict - No part of a building may stand within 20 ft of any street or 15 ft of any lot line, and any two buildings that do not share a party wall must be at least 30 ft apart.

  • Dwelling units are a conditional use here, not a use of right, at 15 dwelling units per acre under § 270-23.
  • A Planned Waterfront special permit, for an assembled site of at least 3 acres, allows 22 dwelling units per acre, and the Planning Board may carry that to 32 in exchange for amenities.
  • Parking and loading areas must sit at least 10 ft from any street or lot line.
  • At least 15% of the lot area must be open space.
  • A studio or efficiency apartment must be at least 600 sq ft, a one-bedroom 750 and a two-bedroom 900, with another 350 sq ft for each additional bedroom.
  • Under that special permit at least 10% of the units must be studios or one-bedrooms and 20% two-bedrooms.

Central Waterfront - Transit-Oriented Subdistrict - No part of a building may stand within 20 ft of any street or 15 ft of any lot line, and any two buildings that do not share a party wall must be at least 50 ft apart.

  • Dwelling units are a conditional use here, not a use of right, at 15 dwelling units per acre under § 270-23.
  • A Planned Waterfront special permit, for an assembled site of at least 3 acres, allows 22 dwelling units per acre, and the Planning Board may carry that to 32 in exchange for amenities.
  • No building may rise more than 1 story or 16 ft above Market or Hunter Streets.
  • Parking and loading areas must sit at least 10 ft from any street or lot line.
  • Pedestrian entrances on the Main, Secor, Central and Water Street frontages may be no more than 70 ft apart, and parking may take no more than 30% of a lot frontage on those streets.
  • At least 15% of the lot area must be open space.

Central Waterfront - Hillside Subdistrict - No building may be erected to a height exceeding 220 ft above sea level, and any two buildings that do not share a party wall must be at least 25 ft apart.

  • Dwelling units are a conditional use here, not a use of right.
  • The only residential density stated here comes with a Planned Waterfront special permit, for an assembled site of at least 3 acres: 22 dwelling units per acre, rising to 32 by a Planning Board bonus.
  • At least 15% of the lot area must be open space.
  • A studio or efficiency apartment must be at least 600 sq ft, a one-bedroom 750 and a two-bedroom 900, with another 350 sq ft for each additional bedroom.
  • Under that special permit at least 10% of the units must be studios or one-bedrooms and 20% two-bedrooms.
  • Buildings must be laid out under the building width and open area rules of § 270-23.

Office-Research District - On a lot abutting a residential district the side yard rises from 50 ft to 75 ft, and a rear yard abutting one needs a buffer of at least 20 ft on top of the setback, screened.

  • Parking and loading areas must sit at least 50 ft from any street or lot line.
  • Residential dwelling units are not permitted here.
  • No side yard or rear yard is required where that yard abuts an operating railroad right-of-way, § 270-28B.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-28F.

General Business District - A rear yard abutting a residential district needs a buffer of at least 15 ft on top of the setback, and every buffer must be screened.

  • Parking and loading areas must sit at least 5 ft from any street or lot line.
  • Residential dwelling units are not permitted here.
  • No side yard or rear yard is required where that yard abuts an operating railroad right-of-way, § 270-28B.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-28F.

Neighborhood Center District - The 10 ft side yard is required only for lots abutting a residential district, and a rear yard abutting one needs a 10 ft buffer on top of the setback, screened.

  • Residential dwelling units are a conditional use here, not a use of right.
  • A studio or efficiency apartment must be at least 600 sq ft, a one-bedroom 750 and a two-bedroom 900, with another 350 sq ft for each additional bedroom.
  • This district may also be developed under the optional Croton Avenue and Downtown Overlay standards of § 270-15.1, which set their own heights and coverage.
  • On a sloped lot the ground floor, where dwellings are barred, is the whole floor level with the main entrance, under a 2026 amendment.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-28F.

Neighborhood Center District - The front yard may be no more than 15 ft deep, and the 10 ft side yard is required only for lots abutting a residential district.

  • Residential dwelling units are a conditional use here, not a use of right.
  • A rear yard abutting a residential district needs a buffer of at least 10 ft on top of the setback, and every buffer must be screened.
  • A studio or efficiency apartment must be at least 600 sq ft, a one-bedroom 750 and a two-bedroom 900, with another 350 sq ft for each additional bedroom.
  • This district may also be developed under the optional Croton Avenue Overlay standards of § 270-15.1, which set their own heights and coverage.
  • On a sloped lot the ground floor, where dwellings are barred, is the whole floor level with the main entrance, under a 2026 amendment.

Professional Office District - On a lot wider than the district minimum, the two side yards must together equal 40% of the lot width, and each side yard must be at least 45% of that total.

  • Two-family and multifamily dwellings are conditional uses here, and every dwelling unit, of whatever kind, must have at least 800 sq ft of livable floor area, § 270-17C.
  • An applicant for a residential use must provide affordable housing under Chapter 62.
  • No side yard or rear yard is required where that yard abuts an operating railroad right-of-way, § 270-28B.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-28F.

Planned Center District - The 20 ft side yard is required only for lots abutting a residential district, and a rear yard abutting one needs a buffer of at least 20 ft on top of the setback, screened.

  • Parking and loading areas must sit at least 20 ft from any street or lot line.
  • Residential dwelling units are not permitted here.
  • No side yard or rear yard is required where that yard abuts an operating railroad right-of-way, § 270-28B.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-28F.

Station Plaza South District - No part of a building may stand within 15 ft of a street or lot line, and the lot must be at least 1 acre.

  • Parking and loading areas must sit at least 5 ft from any street or lot line.
  • Residential dwelling units are not permitted here.
  • No side yard or rear yard is required where that yard abuts an operating railroad right-of-way, § 270-28B.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-28F.

Station Plaza North District - A building may sit no further than 10 ft from the front lot line, and a rear yard abutting a residential district needs a 10 ft buffer, screened.

  • A moratorium adopted in July 2025 suspends the processing and approval of applications to build residential units in this district; confirm with the building department whether it is still in force.
  • Residential dwelling units are a conditional use here, and a studio or efficiency apartment must be at least 600 sq ft, a one-bedroom 750 and a two-bedroom 900.
  • A local law adopted in August 2026 makes single-, two-, three- and four-family buildings and mixed-use buildings of up to six units conditional uses here.
  • Under that law a single-family house sits on 1,500 sq ft of lot with 5 ft side yards, 10 ft for both, a 10 ft rear yard, 2 1/2 stories or 35 ft and 70% building coverage.
  • The lot rises to 4,000 sq ft for a four-family building.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-28F.

Village Center District - The front yard may be no more than 10 ft deep, and a rear yard abutting a residential district needs a 10 ft buffer on top of the setback, screened.

  • Residential dwelling units are a conditional use here, not a use of right.
  • A studio or efficiency apartment must be at least 600 sq ft, a one-bedroom 750 and a two-bedroom 900, with another 350 sq ft for each additional bedroom.
  • This district may also be developed under the optional Downtown Overlay standards of § 270-15.1, which allow 4 stories and 48 ft, or 5 stories and 58 ft with a density bonus by special permit.
  • On a sloped lot the ground floor, where dwellings are barred, is the whole floor level with the main entrance, under a 2026 amendment.
  • Any property that adjoins or contains a watercourse must keep a buffer of 25 ft on each side of it, § 270-28F.
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Costs an ADU adds that a house does not

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Building a full house instead?

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

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
Rye (City)
800 sq ft ≈ $235k–310k
White Plains (City)
800 sq ft ≈ $235k–310k
Yonkers (City)
800 sq ft ≈ $235k–310k

All Westchester County towns: Mount Vernon (City) · New Rochelle (City) · Peekskill (City) · Rye (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) · Pelham (Village) · Pelham Manor (Village) · Pleasantville (Village) · Port Chester (Village) · Rye Brook (Village) · Scarsdale (Village) · Sleepy Hollow (Village) · Tarrytown (Village) · Tuckahoe (Village)

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

ADU cost in Ossining: common questions

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

An 800 sq ft accessory dwelling unit in Village of Ossining 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 Ossining?

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 Ossining?

Village of Ossining has 23 districts. All districts prohibit ADUs. Check the specific address with the free ADU checker or confirm with the building department at (914) 941-3199 before you spend money on design.

Can I rent an ADU in Ossining short term?

No local short-term-rental law on record - which is not the same as permission for Village of Ossining. 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 Village of Ossining vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-09-26; verify with the building department at (914) 941-3199 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.

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