Hastings-on-Hudson · ADU cost
What it costs to build an ADU in Hastings-on-Hudson, NY
An 800 sq ft accessory dwelling unit in Hastings-on-Hudson 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 Hastings-on-Hudson maps 24 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 Hastings-on-Hudson
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 Hastings-on-Hudson 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 |
|---|---|---|---|---|
| Marine Waterfront | 0.4591 ac | — | 30 ft | No |
| One-Family Residence | 0.4591 ac | — | 35 ft | Occupancy restricted |
| Two Family Residence | 0.1722 ac | — | 35 ft | Occupancy restricted |
| One-Family Residence | 0.2296 ac | — | 35 ft | Occupancy restricted |
| One-Family Residence | 0.1722 ac | — | 35 ft | Occupancy restricted |
| Two Family Residence | 0.0803 ac | — | 35 ft | Occupancy restricted |
| Multi-Family Residence/Office | 0.1148 ac | — | 40 ft | Occupancy restricted |
| Multi-Family Residence | 0.0344 ac | — | 40 ft | Occupancy restricted |
| Multi-Family Residence | 0.0574 ac | — | 35 ft | Occupancy restricted |
| Multi-Family Residence/Commercial | 0.0574 ac | — | 40 ft | Occupancy restricted |
| Limited Office | 4 ac | — | 40 ft | No |
| Central Commercial | 0.0574 ac | — | 40 ft | No |
| Central Office | 0.2296 ac | — | 35 ft | No |
| Limited Commercial | 0.9183 ac | — | 35 ft | No |
| General Industry | 0.6887 ac | — | 40 ft | No |
| Limited Industry | 0.4591 ac | — | 40 ft | No |
| Mixed Use Planned Development | — | — | — | No |
| Public Park, Recreation and Playground | — | — | — | No |
| Conservation/Cluster Housing | — | — | — | — |
| Cluster Zone Overlay | — | — | — | — |
| Gateway Cluster Overlay District | — | — | — | — |
| Multimedia Production Studio Overlay | — | — | — | — |
| Personal Wireless Facilities Overlay District | — | — | — | — |
| View Preservation Overlay | — | — | — | — |
Size limits on record in Hastings-on-Hudson
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 Hastings-on-Hudson:
- One-Family Residence§ 295-53.2B names R-20 among the nine districts where one ADU “shall be permitted” on a lot with a single-family residence as the principal use. Approval is ministerial — the Building Inspector issues the permit where every condition of Subsection B is met without a waiver and the unit is not in a new accessory structure built after 10-31-2025 (C(3)) — but the owner must occupy one of the units on the premises as a principal residence (B(1)), which is why this is special-provisions. May be in the principal building or a conforming accessory building. 300 sq ft minimum and ≤ 33% of the principal dwelling; max two bedrooms; one parking space plus one per extra bedroom. PERMIT LASTS FIVE YEARS and renewal requires notice to owners within 300 feet (C(7)); a new owner must file within 90 days of taking title or the approval is revoked (C(8)).
- One-Family Residence§ 295-53.2B names R-10. One ADU permitted on a lot with a single-family residence as the principal use; the Building Inspector issues the permit where no waiver is needed and the unit is not in a post-10-31-2025 accessory structure (C(3)). Owner must occupy one of the units as a principal residence (B(1)). Principal building or conforming accessory building; 300 sq ft minimum and ≤ 33% of the house; max two bedrooms. Five-year permit with 300-foot renewal notice; new owner must file within 90 days of taking title.
- One-Family Residence§ 295-53.2B names R-7.5. One ADU permitted on a lot with a single-family residence as the principal use, issued ministerially by the Building Inspector absent a waiver (C(3)). Owner-occupancy of one unit as a principal residence required (B(1)). Principal building or conforming accessory building; 300 sq ft minimum and ≤ 33% of the house; max two bedrooms. Five-year permit with 300-foot renewal notice; new owner must file within 90 days.
- Multi-Family Residence/OfficeMR-O is the Multifamily Residence/Office district (§ 295-6) and is named in § 295-53.2B. The ADU attaches only where the lot's principal use is a single-family residence. Owner-occupancy of one unit as a principal residence required (B(1)); the Building Inspector issues the permit absent a waiver (C(3)). 300 sq ft minimum and ≤ 33% of the house; max two bedrooms. Five-year permit with 300-foot renewal notice.
- Multi-Family ResidenceMR-1.5 is a Multifamily Residence district (§ 295-6) and is named in § 295-53.2B. The ADU attaches only where the lot's principal use is a single-family residence. Owner must occupy one of the units as a principal residence (B(1)); the Building Inspector issues the permit absent a waiver (C(3)). Principal building or conforming accessory building; 300 sq ft minimum and ≤ 33% of the house; max two bedrooms. Five-year permit with 300-foot renewal notice.
- Multi-Family ResidenceMR-2.5 is a Multifamily Residence district (§ 295-6) and is named in § 295-53.2B. The ADU attaches only where the lot's principal use is a single-family residence. Owner-occupancy of one unit as a principal residence required (B(1)); ministerial Building Inspector permit absent a waiver. Principal building or conforming accessory building; 300 sq ft minimum and ≤ 33% of the house; max two bedrooms. Five-year permit with 300-foot renewal notice.
- Multi-Family Residence/CommercialMR-C is the Multifamily Residence/Commercial district (§ 295-6) and is named in § 295-53.2B. The ADU attaches only where the lot's principal use is a single-family residence. Owner-occupancy of one unit as a principal residence required (B(1)); ministerial Building Inspector permit absent a waiver. 300 sq ft minimum and ≤ 33% of the house; max two bedrooms. Five-year permit with 300-foot renewal notice.
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. No local STR ordinance found as of Jun 2026; standard village zoning and building codes apply. Westchester County hotel occupancy tax (3%) applies to short-term stays. Separate question from whether you can build the unit.
- Building dept(914) 478-3400
Sizing up a specific parcel in Hastings-on-Hudson?
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 Hastings-on-Hudson runs $242–318/sq ft, about $435k–570k at 1,800 sq ft . See what it costs to build a house in Hastings-on-Hudson.
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 · Greenburgh · 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) · 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 Hastings-on-Hudson: Can you build an ADU here? · Zoning for new construction · Westchester County build cost
ADU cost in Hastings-on-Hudson: common questions
How much does it cost to build an ADU in Hastings-on-Hudson, NY?
An 800 sq ft accessory dwelling unit in Village of Hastings-on-Hudson 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 Hastings-on-Hudson?
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 Hastings-on-Hudson?
Village of Hastings-on-Hudson has 24 districts. 9 districts prohibit ADUs, 9 allow them with occupancy restrictions. 6 districts have incomplete data - verify with the building department at (914) 478-3400. Check the specific address with the free ADU checker before you spend money on design.
Can I rent an ADU in Hastings-on-Hudson short term?
No local short-term-rental law on record - which is not the same as permission for Village of Hastings-on-Hudson. 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 Hastings-on-Hudson vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-06-08; verify with the building department at (914) 478-3400 before relying on any answer. Sources: Offsite / Aldo cost engine (costEngine.js + constants.js); zoning dataset (municipalData.js).