Stockport · ADU cost
What it costs to build an ADU in Stockport, NY
An 800 sq ft accessory dwelling unit in Stockport runs roughly $195k–260k, or about $247–323/sq ft, and that per-square-foot figure sits deliberately above the $202–265/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 Stockport maps 4 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 Stockport
Standard finish, slab on grade, on a flat and clear part of the lot, general-contractor margin included. These are structure costs at Columbia County pricing, before the service and septic work a second dwelling can trigger.
| Size | Type | $ / sq ft | Estimated total |
|---|---|---|---|
| 400 sq ft | Studio | $327–$428 | $130k–170k |
| 600 sq ft | One bedroom | $273–$358 | $165k–215k |
| 800 sq ft | One bedroom, larger | $247–$323 | $195k–260k |
| 1,000 sq ft | Two bedroom | $231–$302 | $230k–300k |
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 | $27–$33 | $16 | 55% |
| Electrical | $18–$23 | $13 | 35% |
| HVAC | $23–$28 | $14 | 45% |
| Insulation | $7–$9 | $7 | — |
| Interior finishes | $32–$43 | $27 | 15% |
| Millwork & cabinetry | $18–$27 | $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 Stockport 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 |
|---|---|---|---|---|
| Hamlet | 1 ac | 20 / 10 / 30 ft | 35 ft | Occupancy restricted |
| Residential | 1 ac | 25 / 20 / 50 ft | 35 ft | Occupancy restricted |
| Rural Residential | 3 ac | 40 / 25 / 50 ft | 35 ft | Occupancy restricted |
| Commercial/Light Industrial | 0.5 ac | 100 / 50 / 100 ft | 35 ft | No |
Hamlet - The figures shown are for lots with central water only. With common sewer as well, the schedule prints a second Hamlet row where the figures drop by two thirds.
- With central water and common sewer the minimum lot area per dwelling unit falls from one acre to 0.3333 acre, and the density from one unit per acre to 21,780 sq ft, half an acre.
- Minimum open space is 40%.
- A nonresidential use is limited to one principal building per acre, or per half acre with sewer.
- The density figure, which governs how many dwellings a parcel yields, is larger than the minimum lot area per dwelling unit, which is the floor under each lot.
Residential - The figures shown are for lots with central water. The schedule prints two rows for R, and they differ only in density, not in minimum lot area.
- Without central water the density falls from 1 dwelling per acre to one per 1.5 acres, while the minimum lot area per dwelling unit stays at one acre in both rows.
- Minimum open space is 60%.
- A nonresidential use is limited to one principal building per 1.5 acres.
- The density figure, which governs how many dwellings a parcel yields, is larger than the minimum lot area per dwelling unit, which is the floor under each lot.
Rural Residential - The schedule sets a density of one dwelling per three acres, which governs how many dwellings a parcel yields, and a separate minimum lot area per dwelling unit of one acre.
- Minimum open space is 70%.
- A nonresidential use is limited to one principal building per three acres.
Commercial/Light Industrial - The half-acre minimum is the lot area per principal building for nonresidential uses; the schedule publishes no residential standard in CLI. No commercial retail structure may exceed a 10,000 sq ft building footprint.
- Minimum open space is 40%.
Size limits on record in Stockport
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 Stockport:
- HamletNo more than 35% of the existing structure's habitable space before conversion, or 1,000 square feet in a new structure; one per principal residence, with at most two bedrooms.
- ResidentialNo more than 35% of the existing structure's habitable space before conversion, or 1,000 square feet in a new structure; one per principal residence, with at most two bedrooms.
- Rural ResidentialNo more than 35% of the existing structure's habitable space before conversion, or 1,000 square feet in a new structure; one per principal residence, with at most two bedrooms.
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 Central Hudson 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. Stockport 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/12912293
- Building dept(518) 828-9389
Sizing up a specific parcel in Stockport?
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 Stockport runs $202–265/sq ft, about $365k–475k at 1,800 sq ft , plus roughly $9,221 for a conforming lot. See what it costs to build a house in Stockport.
ADU cost in nearby towns
All Columbia County towns: Hudson (City) · Ancram · Austerlitz · Canaan · Chatham · Claverack · Clermont · Copake · Gallatin · Germantown · Ghent · Hillsdale · Kinderhook · Livingston · New Lebanon · Stuyvesant · Taghkanic · Chatham (Village) · Kinderhook (Village) · Philmont (Village) · Valatie (Village)
More on Stockport: Can you build an ADU here? · Zoning for new construction · Columbia County build cost
ADU cost in Stockport: common questions
How much does it cost to build an ADU in Stockport, NY?
An 800 sq ft accessory dwelling unit in Town of Stockport runs roughly $195k–260k at a standard finish, general-contractor margin included. A 400 sq ft studio runs about $130k–170k. 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 Stockport?
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 $247–323/sq ft against $202–265/sq ft for a full house, even though it is the same trades doing the same work.
Are ADUs allowed in Stockport?
Town of Stockport has 4 districts. 3 districts allow ADUs with occupancy restrictions, 1 does not. Check the specific address with the free ADU checker or confirm with the building department at (518) 828-9389 before you spend money on design.
Can I rent an ADU in Stockport short term?
No local short-term-rental law on record - which is not the same as permission for Town of Stockport. 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 Columbia 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 Stockport vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-07-15; verify with the building department at (518) 828-9389 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.