Stillwater · ADU cost
What it costs to build an ADU in Stillwater, NY
An 800 sq ft accessory dwelling unit in Stillwater runs roughly $200k–260k, or about $249–327/sq ft, and that per-square-foot figure sits deliberately above the $204–268/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 Stillwater maps 3 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 Stillwater
Standard finish, slab on grade, on a flat and clear part of the lot, general-contractor margin included. These are structure costs at Saratoga County pricing, before the service and septic work a second dwelling can trigger.
| Size | Type | $ / sq ft | Estimated total |
|---|---|---|---|
| 400 sq ft | Studio | $331–$433 | $130k–175k |
| 600 sq ft | One bedroom | $276–$362 | $165k–215k |
| 800 sq ft | One bedroom, larger | $249–$327 | $200k–260k |
| 1,000 sq ft | Two bedroom | $233–$305 | $235k–305k |
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 | $7–$11 | $7 | — |
| Foundation | $16–$23 | $16 | — |
| Framing | $25–$32 | $25 | — |
| Envelope - roof, siding, windows | $32–$41 | $32 | — |
| Plumbing | $28–$34 | $16 | 55% |
| Electrical | $18–$24 | $13 | 35% |
| HVAC | $23–$28 | $15 | 45% |
| Insulation | $7–$9 | $7 | — |
| Interior finishes | $32–$43 | $27 | 15% |
| Millwork & cabinetry | $18–$28 | $11 | 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 Stillwater 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 |
|---|---|---|---|---|
| V3 Neighborhood | 0.23 ac | 15 / 10 / 20 ft | 35 ft | Occupancy restricted |
| V4 Mixed Use | 0.11 ac | 0 / 5 / 5 ft | 40 ft | Occupancy restricted |
| V5 Mixed Use Center | 0.11 ac | 0 / 5 / 5 ft | 40 ft | Occupancy restricted |
V3 Neighborhood - These figures are necessary but not sufficient. The regulating plan also fixes build-to lines, private frontage types, window transparency minimums, entrance and orientation rules, massing breaks every 50 ft in a linear row, and materials and colours.
- A parcel that satisfies the lot and setback figures can still fail the code on frontage type, entrance placement or transparency, with the Route 4 corridor design guidelines layered on top.
- A one-family dwelling and an accessory dwelling unit are both permitted by right, so a second unit comes far more easily as an accessory unit than as a duplex.
- A two-family dwelling needs a special use permit here, a three- or four-family needs one too, and multifamily of five or more is not permitted at all.
- Agriculture, agricultural tourism and roadside farm stands are permitted by right here, and a manufactured home or park, a cemetery or a self-storage facility is available by special use permit.
V4 Mixed Use - The figures shown are the non-waterfront case. On a waterfront parcel the side yard is 10 ft rather than 5 ft and the height drops to 2 stories or 35 ft, so establish which side of that line a parcel falls on first.
- The front figure is a build-to band with a ceiling, not a minimum: build to the sidewalk or at most 10 ft from the frontage line, with 15 ft allowed only for outdoor dining or a plaza.
- Pushing a building back beyond that band is a violation, not a courtesy.
- There is no side yard setback at all for buildings sharing a party wall.
- One-family, two-family and accessory dwelling units are permitted by right, and multifamily of five or more, mixed-use buildings, live-work units, retail and hotels go through site plan review.
- Craft production, light industrial, drive-through windows and fast-food restaurants need a special use permit.
- The regulating plan also fixes build-to lines, frontage types, window transparency, entrance and orientation rules, massing breaks every 50 ft in a linear row, and materials and colours.
V5 Mixed Use Center - The front figure is a build-to band with a ceiling, not a minimum: build to the sidewalk or at most 10 ft from the frontage line, with 15 ft allowed only for outdoor dining or a plaza. A fourth storey is available by bonus rather than by right.
- The bonus is worth a whole storey: a building may reach 4 stories or 50 feet where a listed public benefit is provided and the Village Board of Trustees approves it.
- The affordable route asks at least 10% of the units, deed restricted for not less than 30 years at 50 to 80% of HUD median household income; historic reuse and LEED design also qualify.
- Pushing a building back beyond that band is a violation, not a courtesy.
- There is no side yard setback at all for buildings sharing a party wall.
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 National Grid 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. The Village of Stillwater has no local short-term rental law, and that is not the same as permission. Confirm the Village's position in writing before counting on short-stay income. Separate question from whether you can build the unit.
- Zoning codevillageofstillwaterny.gov/wp-content/uploads/2022/05/Form-Based-Code-Amended-2020-07-21-w-Tables-and-Map.pdf
- Building dept(518) 664-6258
Sizing up a specific parcel in Stillwater?
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 Stillwater runs $204–268/sq ft, about $370k–480k at 1,800 sq ft . See what it costs to build a house in Stillwater.
ADU cost in nearby towns
All Saratoga County towns: Mechanicville (City) · Saratoga Springs (City) · Ballston · Charlton · Clifton Park · Corinth · Day · Edinburg · Galway · Greenfield · Halfmoon · Malta · Milton · Moreau · Northumberland · Providence · Saratoga · Stillwater · Waterford · Wilton · Ballston Spa (Village) · Corinth (Village) · Round Lake (Village) · Schuylerville (Village) · South Glens Falls (Village) · Victory (Village) · Waterford (Village)
More on Stillwater: Can you build an ADU here? · Zoning for new construction · Saratoga County build cost
ADU cost in Stillwater: common questions
How much does it cost to build an ADU in Stillwater, NY?
An 800 sq ft accessory dwelling unit in Village of Stillwater runs roughly $200k–260k at a standard finish, general-contractor margin included. A 400 sq ft studio runs about $130k–175k. 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 Stillwater?
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 $249–327/sq ft against $204–268/sq ft for a full house, even though it is the same trades doing the same work.
Are ADUs allowed in Stillwater?
Village of Stillwater has 3 districts. All districts allow ADUs with occupancy restrictions. Check the specific address with the free ADU checker or confirm with the building department at (518) 664-6258 before you spend money on design.
Can I rent an ADU in Stillwater short term?
No local short-term-rental law on record - which is not the same as permission for Village of Stillwater. 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 Saratoga 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 Stillwater vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-08-02; verify with the building department at (518) 664-6258 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.