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 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 Stillwater maps 11 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 |
|---|---|---|---|---|
| CSR Cold Spring Road Transition | 2 ac | 50 / 25 / 25 ft | 35 ft | As of right |
| SLZ-1 Saratoga Lake Zone-1 | 0.34 ac | 20 / 15 / 30 ft | 30 ft | As of right |
| R76 Route 76 Crossroads | 0.34 ac | 30 / 15 / 20 ft | 35 ft | No |
| MB Mixed-Use Business | 1 ac | 50 / 35 / 35 ft | 50 ft | No |
| R67 Route 67 Mixed-Use | 1 ac | 50 / 35 / 35 ft | 50 ft | No |
| T2 Rural Conservation | 1.5 ac | 50 / 25 / 30 ft | 35 ft | As of right |
| T3N Neighborhood | 0.23 ac | 35 / 20 / 30 ft | 35 ft | As of right |
| T3G Gateway | 0.14 ac | 35 / 15 / 10 ft | 35 ft | As of right |
| T3G-1 Rural Gateway | 0.23 ac | 35 / 20 / 30 ft | 35 ft | As of right |
| T4 Riverfront Corridor | 0.14 ac | 15 / 15 / 10 ft | 40 ft | As of right |
| T5 Gateway | 0.11 ac | 0 / 0 / 5 ft | 40 ft | As of right |
CSR Cold Spring Road Transition - The 2 acres is required per dwelling unit and does not change with public water or sewer, so a duplex needs four acres.
- Setback and width requirements do not apply to agricultural uses and roadside stands.
- The 200 ft figure is required road frontage, not lot width at the building line.
SLZ-1 Saratoga Lake Zone-1 - The 15,000 sq ft is required per dwelling unit, so a duplex needs twice that. The 75 ft figure is required road frontage, not lot width at the building line.
- The Saratoga Lake watershed overlay district (§ 210-13) applies over this area and sets watershed protection requirements, though no lot or bulk standards of its own.
R76 Route 76 Crossroads - The 15,000 sq ft is a flat lot minimum here, not an amount of land required per dwelling unit.
- The 60 ft figure is required road frontage, not lot width at the building line.
MB Mixed-Use Business - The one-acre minimum is a flat lot area here, not an amount of land required per dwelling unit.
- The 200 ft figure is required road frontage, not lot width at the building line.
R67 Route 67 Mixed-Use - Land per dwelling unit depends on utilities: 1 acre with both public water and sewer, 2 acres with either, and 3 acres with neither.
- On an unserviced parcel a four-unit proposal needs 12 acres, which is the steepest utility penalty in the town.
- The land figure applies per dwelling unit, so a duplex needs twice that.
- The 200 ft figure is required road frontage, not lot width at the building line.
T2 Rural Conservation - Land per dwelling unit is 1.5 acres with public water or sewer or both, and 2 acres with neither.
- The land figure applies per dwelling unit, so a duplex needs twice that.
- Height is limited to 2 stories or 35 feet, and both limits apply.
- The 200 ft figure is required road frontage, not lot width at the building line.
T3N Neighborhood, T3G-1 Rural Gateway - Land per dwelling unit is 10,000 sq ft with both public water and sewer, 20,000 sq ft with either, and a full acre with neither.
- Without either utility that is 1 acre, 43,560 sq ft, per dwelling unit, more than four times the fully serviced 10,000 sq ft.
- The land figure applies per dwelling unit, so a duplex needs twice that.
- Height is limited to 2 stories or 35 feet, and both limits apply.
- The 150 ft figure is required road frontage, not lot width at the building line.
T3G Gateway - The 6,000 sq ft is required per dwelling unit and does not change with public water or sewer, so a duplex needs twice that.
- Height is limited to 2 stories or 35 feet, and both limits apply.
- The 50 ft figure is required road frontage, not lot width at the building line.
T4 Riverfront Corridor - The 6,000 sq ft is required per dwelling unit, so a duplex needs twice that. Height is limited to 3 stories or 40 feet, and both limits apply.
- The 50 ft figure is required road frontage, not lot width at the building line.
T5 Gateway - The front and side setbacks are build-to bands: the front may be 0 to 10, or 0 to 15 where an outdoor dining area or plaza fills the extra depth, and the side 0 to 5.
- A building may not be set back past the top of either band.
- The 5,000 sq ft is required per dwelling unit, so a duplex needs twice that.
- Height is limited to 3 stories or 40 feet, and both limits apply.
- The 50 ft figure is required road frontage, not lot width at the building line.
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 Town of Stillwater has no local short-term rental law, and that is not the same as permission. Confirm with the Building Department before counting on short-term rental income. Separate question from whether you can build the unit.
- Zoning codeecode360.com/11864537
- Building dept(518) 664-6148 x215
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 , plus roughly $3,122 for a conforming lot. 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 · Waterford · Wilton · Ballston Spa (Village) · Corinth (Village) · Round Lake (Village) · Schuylerville (Village) · South Glens Falls (Village) · Stillwater (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 Town 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?
Town of Stillwater has 11 districts. 8 districts allow ADUs, 3 do not. Check the specific address with the free ADU checker or confirm with the building department at (518) 664-6148 x215 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 Town 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 Town of Stillwater vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-07-31; verify with the building department at (518) 664-6148 x215 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.