Greenburgh · ADU cost
What it costs to build an ADU in Greenburgh, NY
An 800 sq ft accessory dwelling unit in Greenburgh 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 town 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 Town of Greenburgh maps 27 districts that treat accessory units differently from one another, so read the table below as a starting point rather than a verdict.
ADU cost by size in Greenburgh
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.
| Size | Type | $ / sq ft | Estimated 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 ADU | If it scaled with floor area | Fixed 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 Greenburgh 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 Residence | 0.6887 ac | — | 25 ft | Occupancy restricted |
| One-Family Residence | 0.9183 ac | — | 25 ft | Occupancy restricted |
| Multifamily | 0.1607 ac | — | 25 ft | No |
| Planned Unit Development | 2.5 ac | — | — | Occupancy restricted |
| One-Family Residence | 0.2296 ac | — | 25 ft | Occupancy restricted |
| One-Family Residence | 0.3444 ac | — | 25 ft | Occupancy restricted |
| One-Family Residence | 0.4591 ac | — | 25 ft | Occupancy restricted |
| One-Family Residence | 0.1148 ac | — | 25 ft | Occupancy restricted |
| One-Family Residence | 0.1722 ac | — | 25 ft | Occupancy restricted |
| Multifamily Residence | 0.0918 ac | — | 38 ft | No |
| Multifamily Residence | 0.0689 ac | — | 38 ft | No |
| Scatter-Site Public Housing | 0.1033 ac | — | 25 ft | No |
| Multifamily Residence | 0.0459 ac | — | 38 ft | No |
| High-Rise Multifamily Residence | 0.0402 ac | — | 68 ft | No |
| High-Rise Multifamily Residence | 0.0057 ac | — | 68 ft | No |
| Central Avenue Mixed-Use Impact | — | — | 48 ft | No |
| Close Business | — | — | 25 ft | No |
| Designed Shopping | 0.2296 ac | — | 40 ft | No |
| Hartsdale Center | — | — | 30 ft | No |
| Intermediate Business | — | — | 25 ft | No |
| Limited Office Business | 0.4591 ac | — | 55 ft | No |
| Office Business | 1.8365 ac | — | 75 ft | No |
| Office Business | 1.8365 ac | — | 75 ft | No |
| General Industrial | 1.8365 ac | — | 45 ft | No |
| Light Industrial | 0.9183 ac | — | 45 ft | No |
| Nonresidential Planned Development | 35 ac | — | 40 ft | No |
| Urban Renewal | — | — | — | No |
Size limits on record in Greenburgh
Where the code states a size cap, it decides which row of the cost table above actually applies to you. These are the caps recorded for Greenburgh:
- One-Family ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- One-Family ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- MultifamilyMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Planned Unit DevelopmentMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- One-Family ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- One-Family ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- One-Family ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- One-Family ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- One-Family ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Multifamily ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Multifamily ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Scatter-Site Public HousingMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Multifamily ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- High-Rise Multifamily ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- High-Rise Multifamily ResidenceMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Central Avenue Mixed-Use ImpactMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Close BusinessMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Designed ShoppingMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Hartsdale CenterMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Intermediate BusinessMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Limited Office BusinessMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Office BusinessMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Office BusinessMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- General IndustrialMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Light IndustrialMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Nonresidential Planned DevelopmentMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
- Urban RenewalMinimum lot turns on form: 20,000 sq ft for a new detached structure, 10,000 sq ft to expand the dwelling, 7,500 sq ft to convert inside it — never under 7,500 sq ft
Costs an ADU adds that a house does not
- Septic and water A second dwelling adds bedrooms to the design flow, which on an unsewered parcel often means expanding or replacing the existing system rather than tapping it. This is the single most common reason an ADU budget moves after design, and it is site-specific enough that no model should quote it - get it evaluated early.
- Utility service Con Edison territory. A detached unit needs power run to it, and whether it goes on its own meter or subfeeds the main house changes both the cost and the permit path.
- Access and parking Many codes require an added parking space for the accessory unit, and a detached unit usually needs a driveway extension or a path, both of which count against a lot-coverage or impervious-surface cap.
- Short-term rentalsNo local short-term-rental law on record - which is not the same as permission. Town FAQ states STRs 'are not listed as a permitted use in the Town of Greenburgh in any residential zoning district.' No local STR ordinance or permit pathway exists in the municipal code as of Jun 2026; STRs are effectively prohibited by zoning. Separate question from whether you can build the unit.
- Building dept(914) 989-1560
Sizing up a specific parcel in Greenburgh?
Aldo pulls the exact zoning district, setbacks, and build feasibility for any parcel — before you buy. Enter your email to open Aldo and run your free report.
Building a full house instead?
A standard-finish house in Greenburgh runs $242–318/sq ft, about $435k–570k at 1,800 sq ft . See what it costs to build a house in Greenburgh.
ADU cost in nearby towns
All Westchester County towns: Harrison (City) · Mount Vernon (City) · New Rochelle (City) · Peekskill (City) · Rye (City) · White Plains (City) · Yonkers (City) · Bedford · Cortlandt · Eastchester · Lewisboro · Mamaroneck · Mount Pleasant · New Castle · North Castle · North Salem · Ossining · Pound Ridge · Somers · Yorktown · 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 Greenburgh: Can you build an ADU here? · Zoning for new construction · Westchester County build cost
ADU cost in Greenburgh: common questions
How much does it cost to build an ADU in Greenburgh, NY?
An 800 sq ft accessory dwelling unit in Town of Greenburgh 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 Greenburgh?
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 Greenburgh?
Town of Greenburgh has 27 districts. 19 districts prohibit ADUs, 8 allow them with occupancy restrictions. Check the specific address with the free ADU checker or confirm with the building department at (914) 989-1560 before you spend money on design.
Can I rent an ADU in Greenburgh short term?
No local short-term-rental law on record - which is not the same as permission for Town of Greenburgh. 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 Town of Greenburgh vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-06-15; verify with the building department at (914) 989-1560 before relying on any answer. Sources: Offsite / Aldo cost engine (costEngine.js + constants.js); zoning dataset (municipalData.js).