Northumberland · ADU cost
What it costs to build an ADU in Northumberland, NY
An 800 sq ft accessory dwelling unit in Northumberland 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 Northumberland maps 7 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 Northumberland
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 Northumberland 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 |
|---|---|---|---|---|
| Agricultural Protection District (the Town's largest-lot district and its farmland-protection instrument: a single-family dwelling on 5 ACRES with 300 FT of frontage, 50 ft front, 25 ft side and 25 ft rear setbacks, 10% maximum lot coverage and 35 ft height. THE 10% COVERAGE IS THE TIGHTEST IN THE TOWN — half what the residential districts allow and a fifth of the Hamlet's — so even on five acres the built footprint is deliberately constrained. FARMS AND AGRICULTURAL PURSUITS NEED TWICE THE LAND A HOUSE DOES, at 10 ACRES with the same 300 ft of frontage, as do forestry uses and their structures; a farm's setbacks are stated as 'NA', so the farm building itself is unconstrained in placement. That inversion — ten acres to farm, five to build a house — is the district doing its job: it prices the agricultural use as the larger landholding rather than the marginal one. SPECIAL PERMIT USES: farm employee dwelling units at 10 acres, home occupation and bed-and-breakfast and garden shop at 5 acres, nursing home at 5 acres but with 100 ft front and 50 ft side and rear yards, marina and park at 5 acres. MINING IS THE OUTLIER AND THE MOST PERMISSIVE ENTRY IN THE WHOLE SCHEDULE ON LOT SIZE: 1 ACRE, but with 100 FT SETBACKS ON ALL THREE SIDES and no coverage limit at all — the Town trades area for separation exactly as the Village of Corinth does. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.) | 5 ac | 50 / 25 / 25 ft | 35 ft | No |
| R-3 Residential (a single-family dwelling on 3 ACRES with 200 FT of frontage, 50 ft front, 25 ft side and 25 ft rear setbacks, 20% maximum lot coverage and 35 ft height. R-3 sits between the Agricultural Protection District's five acres and R-1's one, and it DOUBLES THE COVERAGE ALLOWANCE FROM 10% TO 20% as it steps down in lot size — so the smaller lot is also the more efficiently buildable one, which is not always the case in this county. The setbacks are identical to APD's and to R-1's: 50-25-25 runs unchanged across all three of the Town's conventional residential districts, so ONLY LOT AREA, FRONTAGE AND COVERAGE DISTINGUISH THEM. A duplex dwelling takes 1 acre with 150 ft of frontage at 30% coverage. THE DUPLEX GETS MORE COVERAGE THAN THE SINGLE-FAMILY HOUSE, which is unusual and worth using: a duplex dwelling here takes the same lot, frontage and setbacks as a single-family dwelling but is allowed 30% lot coverage against the house's 20%. The Town is not charging extra land for the second unit — only asking for a slightly larger footprint allowance to fit it. A bed-and-breakfast is a special permit use at the full 3 acres with 200 ft of frontage. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.) | 3 ac | 50 / 25 / 25 ft | 35 ft | No |
| R-1 Residential (the Town's standard residential district: a single-family dwelling on 1 ACRE with 150 FT of frontage, 50 ft front, 25 ft side and 25 ft rear setbacks, 20% maximum lot coverage and 35 ft height. Setbacks and coverage are identical to R-3's — the districts differ only in lot area and frontage, three acres and 200 ft against one acre and 150 ft. A DUPLEX DWELLING NEEDS NO ADDITIONAL LAND AT ALL: it sits on the same 1 acre with the same 150 ft of frontage and the same 50-25-25 setbacks as a single-family house, and is allowed 30% coverage rather than 20%. THE DUPLEX GETS MORE COVERAGE THAN THE SINGLE-FAMILY HOUSE, which is unusual and worth using: a duplex dwelling here takes the same lot, frontage and setbacks as a single-family dwelling but is allowed 30% lot coverage against the house's 20%. The Town is not charging extra land for the second unit — only asking for a slightly larger footprint allowance to fit it. That makes R-1 the cheapest place in Northumberland to add a second unit, and since the Town has no accessory dwelling unit of any kind, the duplex is the route that matters. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.) | 1 ac | 50 / 25 / 25 ft | 35 ft | No |
| Mobile Home District (BY FAR THE SMALLEST LOT STANDARD IN THE TOWN, and the only one stated in square feet rather than acres: a mobile home ON AN ESTABLISHED LOT IN AN ESTABLISHED MOBILE HOME PARK needs 9,000 SQ FT with 75 ft of frontage, 20 ft front, 20 ft side and 20 ft rear setbacks, 30% maximum lot coverage and 35 ft height. READ THE USE DESCRIPTION CAREFULLY BECAUSE IT IS DOING THE REAL WORK: the entitlement is for a home on an ALREADY ESTABLISHED lot in an ALREADY ESTABLISHED park. It is not a right to create a new mobile home park, and the schedule states no lot area, frontage or standard for a new park anywhere — so the 9,000 sf figure describes infill into existing parks rather than a development opportunity. Anyone reading MH as the Town's affordable-housing district should establish first whether an established park lot actually exists. The 20 ft setbacks on all three sides and the 30% coverage are otherwise the most permissive combination in Northumberland outside the Hamlet. Accessory uses take much shallower yards still — a private garage at 20 ft front and 5 ft side and rear, a storage shed at 25/5/5. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.) | 0.21 ac | 20 / 20 / 20 ft | 35 ft | No |
| C/R Commercial/Residential (a mixed district whose residential standard is IDENTICAL TO R-1 IN EVERY COLUMN — a single-family dwelling on 1 acre with 150 ft of frontage, 50-25-25 setbacks, 20% coverage and 35 ft height — so what distinguishes C/R from R-1 is entirely the use list rather than the buildable envelope, the commercial permissions sitting alongside the housing rather than displacing it. A duplex likewise matches R-1 at 1 acre and 30% coverage. THE DUPLEX GETS MORE COVERAGE THAN THE SINGLE-FAMILY HOUSE, which is unusual and worth using: a duplex dwelling here takes the same lot, frontage and setbacks as a single-family dwelling but is allowed 30% lot coverage against the house's 20%. The Town is not charging extra land for the second unit — only asking for a slightly larger footprint allowance to fit it. A BED-AND-BREAKFAST IS AVAILABLE HERE AT ONLY 1 ACRE with 150 ft of frontage and 20% coverage, against the 3 acres R-3 demands and the 5 acres the Agricultural Protection District demands for the same use — so C/R is by a wide margin the easiest district in Northumberland in which to open one, which matters in a town on the Hudson north of Schuylerville. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.) | 1 ac | 50 / 25 / 25 ft | 35 ft | No |
| Hamlet (the Town's village-scale district and its densest conventional standard: a single-family dwelling on 20,000 SQ FT — under half an acre — with only 100 FT of frontage, a 25 ft front yard, 15 ft side and 20 ft rear, 50% MAXIMUM LOT COVERAGE and 35 ft height. Against R-1 that is a fifth of the lot, two-thirds of the frontage, half the front yard and MORE THAN DOUBLE THE COVERAGE, which together produce a genuine hamlet streetscape rather than a suburban one. THE 50% COVERAGE IS THE HIGHEST IN THE TOWN outside the Industrial district. A DUPLEX DWELLING HERE DOES COST EXTRA LAND, unlike in R-1 and C/R: 40,000 SQ FT, exactly double the single-family figure, at the same 100 ft frontage, 25-15-20 setbacks and 50% coverage. So the Hamlet is the one district where the second unit is priced at a full additional lot. A BED-AND-BREAKFAST NEEDS 1 ACRE HERE — more than double the 20,000 sf a house needs — with a 100 ft frontage and 25 ft front, 20 ft side and rear yards at 50% coverage, so the lodging use is deliberately held to a larger parcel than the dwelling it would occupy. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does. Accessory garages and sheds take 25 ft and 35 ft front yards respectively with 10 ft sides and 15 ft rears.) | 0.46 ac | 25 / 15 / 20 ft | 35 ft | No |
| Industrial (the Town's employment district, and notable for having NO PERMITTED PRINCIPAL USES AT ALL in Attachment A — every entry sits under SPECIAL PERMIT USES, so nothing in the Industrial district is as-of-right and every project goes through the special permit process. Manufacturing and research and development centres each need 1 ACRE with 200 FT of frontage, 50 ft front, 30 ft side and 30 ft rear setbacks, 60% MAXIMUM LOT COVERAGE and 35 ft height. THE 60% COVERAGE IS THE HIGHEST FIGURE IN THE TOWN, and the 200 ft frontage on a one-acre lot is the same width-heavy geometry the Town applies in R-3 — a one-acre lot 200 ft wide is only about 218 ft deep, so an industrial parcel here is broad and shallow by design. Height stays at 35 ft, the same as every other district in Northumberland: THE TOWN APPLIES A SINGLE 35 FT CEILING ACROSS ALL SEVEN DISTRICTS with no exception for industrial or commercial building, which is unusually uniform and will constrain any use needing clear internal height. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.) | 1 ac | 50 / 30 / 30 ft | 35 ft | No |
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Size limits on record in Northumberland
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 Northumberland:
- Agricultural Protection District (the Town's largest-lot district and its farmland-protection instrument: a single-family dwelling on 5 ACRES with 300 FT of frontage, 50 ft front, 25 ft side and 25 ft rear setbacks, 10% maximum lot coverage and 35 ft height. THE 10% COVERAGE IS THE TIGHTEST IN THE TOWN — half what the residential districts allow and a fifth of the Hamlet's — so even on five acres the built footprint is deliberately constrained. FARMS AND AGRICULTURAL PURSUITS NEED TWICE THE LAND A HOUSE DOES, at 10 ACRES with the same 300 ft of frontage, as do forestry uses and their structures; a farm's setbacks are stated as 'NA', so the farm building itself is unconstrained in placement. That inversion — ten acres to farm, five to build a house — is the district doing its job: it prices the agricultural use as the larger landholding rather than the marginal one. SPECIAL PERMIT USES: farm employee dwelling units at 10 acres, home occupation and bed-and-breakfast and garden shop at 5 acres, nursing home at 5 acres but with 100 ft front and 50 ft side and rear yards, marina and park at 5 acres. MINING IS THE OUTLIER AND THE MOST PERMISSIVE ENTRY IN THE WHOLE SCHEDULE ON LOT SIZE: 1 ACRE, but with 100 FT SETBACKS ON ALL THREE SIDES and no coverage limit at all — the Town trades area for separation exactly as the Village of Corinth does. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.)THE HAMLET IS THE EXCEPTION: a duplex needs 40,000 sq ft against a single-family's 20,000 — the second unit is priced at a full additional lot
- R-3 Residential (a single-family dwelling on 3 ACRES with 200 FT of frontage, 50 ft front, 25 ft side and 25 ft rear setbacks, 20% maximum lot coverage and 35 ft height. R-3 sits between the Agricultural Protection District's five acres and R-1's one, and it DOUBLES THE COVERAGE ALLOWANCE FROM 10% TO 20% as it steps down in lot size — so the smaller lot is also the more efficiently buildable one, which is not always the case in this county. The setbacks are identical to APD's and to R-1's: 50-25-25 runs unchanged across all three of the Town's conventional residential districts, so ONLY LOT AREA, FRONTAGE AND COVERAGE DISTINGUISH THEM. A duplex dwelling takes 1 acre with 150 ft of frontage at 30% coverage. THE DUPLEX GETS MORE COVERAGE THAN THE SINGLE-FAMILY HOUSE, which is unusual and worth using: a duplex dwelling here takes the same lot, frontage and setbacks as a single-family dwelling but is allowed 30% lot coverage against the house's 20%. The Town is not charging extra land for the second unit — only asking for a slightly larger footprint allowance to fit it. A bed-and-breakfast is a special permit use at the full 3 acres with 200 ft of frontage. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.)THE HAMLET IS THE EXCEPTION: a duplex needs 40,000 sq ft against a single-family's 20,000 — the second unit is priced at a full additional lot
- R-1 Residential (the Town's standard residential district: a single-family dwelling on 1 ACRE with 150 FT of frontage, 50 ft front, 25 ft side and 25 ft rear setbacks, 20% maximum lot coverage and 35 ft height. Setbacks and coverage are identical to R-3's — the districts differ only in lot area and frontage, three acres and 200 ft against one acre and 150 ft. A DUPLEX DWELLING NEEDS NO ADDITIONAL LAND AT ALL: it sits on the same 1 acre with the same 150 ft of frontage and the same 50-25-25 setbacks as a single-family house, and is allowed 30% coverage rather than 20%. THE DUPLEX GETS MORE COVERAGE THAN THE SINGLE-FAMILY HOUSE, which is unusual and worth using: a duplex dwelling here takes the same lot, frontage and setbacks as a single-family dwelling but is allowed 30% lot coverage against the house's 20%. The Town is not charging extra land for the second unit — only asking for a slightly larger footprint allowance to fit it. That makes R-1 the cheapest place in Northumberland to add a second unit, and since the Town has no accessory dwelling unit of any kind, the duplex is the route that matters. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.)THE HAMLET IS THE EXCEPTION: a duplex needs 40,000 sq ft against a single-family's 20,000 — the second unit is priced at a full additional lot
- Mobile Home District (BY FAR THE SMALLEST LOT STANDARD IN THE TOWN, and the only one stated in square feet rather than acres: a mobile home ON AN ESTABLISHED LOT IN AN ESTABLISHED MOBILE HOME PARK needs 9,000 SQ FT with 75 ft of frontage, 20 ft front, 20 ft side and 20 ft rear setbacks, 30% maximum lot coverage and 35 ft height. READ THE USE DESCRIPTION CAREFULLY BECAUSE IT IS DOING THE REAL WORK: the entitlement is for a home on an ALREADY ESTABLISHED lot in an ALREADY ESTABLISHED park. It is not a right to create a new mobile home park, and the schedule states no lot area, frontage or standard for a new park anywhere — so the 9,000 sf figure describes infill into existing parks rather than a development opportunity. Anyone reading MH as the Town's affordable-housing district should establish first whether an established park lot actually exists. The 20 ft setbacks on all three sides and the 30% coverage are otherwise the most permissive combination in Northumberland outside the Hamlet. Accessory uses take much shallower yards still — a private garage at 20 ft front and 5 ft side and rear, a storage shed at 25/5/5. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.)THE HAMLET IS THE EXCEPTION: a duplex needs 40,000 sq ft against a single-family's 20,000 — the second unit is priced at a full additional lot
- C/R Commercial/Residential (a mixed district whose residential standard is IDENTICAL TO R-1 IN EVERY COLUMN — a single-family dwelling on 1 acre with 150 ft of frontage, 50-25-25 setbacks, 20% coverage and 35 ft height — so what distinguishes C/R from R-1 is entirely the use list rather than the buildable envelope, the commercial permissions sitting alongside the housing rather than displacing it. A duplex likewise matches R-1 at 1 acre and 30% coverage. THE DUPLEX GETS MORE COVERAGE THAN THE SINGLE-FAMILY HOUSE, which is unusual and worth using: a duplex dwelling here takes the same lot, frontage and setbacks as a single-family dwelling but is allowed 30% lot coverage against the house's 20%. The Town is not charging extra land for the second unit — only asking for a slightly larger footprint allowance to fit it. A BED-AND-BREAKFAST IS AVAILABLE HERE AT ONLY 1 ACRE with 150 ft of frontage and 20% coverage, against the 3 acres R-3 demands and the 5 acres the Agricultural Protection District demands for the same use — so C/R is by a wide margin the easiest district in Northumberland in which to open one, which matters in a town on the Hudson north of Schuylerville. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.)THE HAMLET IS THE EXCEPTION: a duplex needs 40,000 sq ft against a single-family's 20,000 — the second unit is priced at a full additional lot
- Hamlet (the Town's village-scale district and its densest conventional standard: a single-family dwelling on 20,000 SQ FT — under half an acre — with only 100 FT of frontage, a 25 ft front yard, 15 ft side and 20 ft rear, 50% MAXIMUM LOT COVERAGE and 35 ft height. Against R-1 that is a fifth of the lot, two-thirds of the frontage, half the front yard and MORE THAN DOUBLE THE COVERAGE, which together produce a genuine hamlet streetscape rather than a suburban one. THE 50% COVERAGE IS THE HIGHEST IN THE TOWN outside the Industrial district. A DUPLEX DWELLING HERE DOES COST EXTRA LAND, unlike in R-1 and C/R: 40,000 SQ FT, exactly double the single-family figure, at the same 100 ft frontage, 25-15-20 setbacks and 50% coverage. So the Hamlet is the one district where the second unit is priced at a full additional lot. A BED-AND-BREAKFAST NEEDS 1 ACRE HERE — more than double the 20,000 sf a house needs — with a 100 ft frontage and 25 ft front, 20 ft side and rear yards at 50% coverage, so the lodging use is deliberately held to a larger parcel than the dwelling it would occupy. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does. Accessory garages and sheds take 25 ft and 35 ft front yards respectively with 10 ft sides and 15 ft rears.)THE HAMLET IS THE EXCEPTION: a duplex needs 40,000 sq ft against a single-family's 20,000 — the second unit is priced at a full additional lot
- Industrial (the Town's employment district, and notable for having NO PERMITTED PRINCIPAL USES AT ALL in Attachment A — every entry sits under SPECIAL PERMIT USES, so nothing in the Industrial district is as-of-right and every project goes through the special permit process. Manufacturing and research and development centres each need 1 ACRE with 200 FT of frontage, 50 ft front, 30 ft side and 30 ft rear setbacks, 60% MAXIMUM LOT COVERAGE and 35 ft height. THE 60% COVERAGE IS THE HIGHEST FIGURE IN THE TOWN, and the 200 ft frontage on a one-acre lot is the same width-heavy geometry the Town applies in R-3 — a one-acre lot 200 ft wide is only about 218 ft deep, so an industrial parcel here is broad and shallow by design. Height stays at 35 ft, the same as every other district in Northumberland: THE TOWN APPLIES A SINGLE 35 FT CEILING ACROSS ALL SEVEN DISTRICTS with no exception for industrial or commercial building, which is unusually uniform and will constrain any use needing clear internal height. Accessory uses carry their own rows and much shallower setbacks than the principal building, with a footnote making the coverage figure the requirement for the PRINCIPAL AND ACCESSORY USES COMBINED rather than a separate allowance — so a garage or shed eats into the same percentage the house does.)THE HAMLET IS THE EXCEPTION: a duplex needs 40,000 sq ft against a single-family's 20,000 — the second unit is priced at a full additional lot
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. No short-term-rental provision exists in the Town of Northumberland Zoning Ordinance. The Ordinance defines no short-term rental, vacation rental or transient-occupancy use, and Attachment A's Schedule of Permitted Uses lists none. There is no registration or licensing requirement. THE ONE ENUMERATED TRANSIENT USE IS THE BED-AND-BREAKFAST, and it is a SPECIAL PERMIT use whose lot requirement varies more than fivefold by district — 5 ACRES in the Agricultural Protection District, 3 ACRES in R-3, 1 ACRE in C/R Commercial/Residential, and 1 ACRE in the Hamlet. THE HAMLET FIGURE IS THE ONE TO NOTICE: a bed-and-breakfast there needs a full acre while a single-family dwelling needs only 20,000 sq ft, so the lodging use is held to MORE THAN DOUBLE the land of the house it would occupy. C/R is by a wide margin the easiest district in which to open one, at a single acre against APD's five for the identical use. Attachment A separates Permitted Principal Uses, Permitted Accessory Uses and Special Permit Uses into distinct blocks per district, so a use appearing in none of the three for a given district has no route to approval there. Recorded 'unknown' rather than 'prohibited' because the Town has never legislated on short-term rental specifically, and whole-house rental of a permitted single-family dwelling is arguably the residential use itself. Absence of a found STR provision is NOT permission. Northumberland sits on the Hudson north of Schuylerville near the Saratoga National Historical Park, so short-stay demand is real and unaddressed. Get a written answer from the Building Department at (518) 792-9179 before underwriting it. Separately, New York State has required every short-term-rental host to register the unit with the State through the county registry since 2025, regardless of what the municipality allows, and Saratoga County HAS adopted a county-level short-term-rental programme: a 3% occupancy tax and a MANDATORY county registry, covering any room or space in a dwelling let for under 30 consecutive days. Registration runs two years, an unregistered host faces fines of up to $500, and the booking platform is separately liable for processing an unregistered listing — so Airbnb and Vrbo will delist. The City of Saratoga Springs runs its own registry alongside it. Separate question from whether you can build the unit.
- Building dept(518) 792-9179
Sizing up a specific parcel in Northumberland?
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Building a full house instead?
A standard-finish house in Northumberland runs $204–268/sq ft, about $370k–480k at 1,800 sq ft , plus roughly $1,248 for a conforming lot. See what it costs to build a house in Northumberland.
ADU cost in nearby towns
Mechanicville (City)
800 sq ft ≈ $200k–260k
Saratoga Springs (City)
800 sq ft ≈ $200k–260k
Ballston
800 sq ft ≈ $200k–260k
Charlton
800 sq ft ≈ $200k–260k
Clifton Park
800 sq ft ≈ $200k–260k
Corinth
800 sq ft ≈ $200k–260k
All Saratoga County towns: Mechanicville (City) · Saratoga Springs (City) · Ballston · Charlton · Clifton Park · Corinth · Day · Edinburg · Galway · Greenfield · Halfmoon · Malta · Milton · Moreau · Providence · Saratoga · Stillwater · Waterford · Wilton · Ballston Spa (Village) · Corinth (Village) · Round Lake (Village) · Schuylerville (Village) · South Glens Falls (Village) · Stillwater (Village) · Victory (Village) · Waterford (Village)
More on Northumberland: Can you build an ADU here? · Zoning for new construction · Saratoga County build cost
ADU cost in Northumberland: common questions
How much does it cost to build an ADU in Northumberland, NY?
An 800 sq ft accessory dwelling unit in Town of Northumberland 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 Northumberland?
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 Northumberland?
Town of Northumberland has 7 districts. All districts prohibit ADUs. Check the specific address with the free ADU checker or confirm with the building department at (518) 792-9179 before you spend money on design.
Can I rent an ADU in Northumberland short term?
No local short-term-rental law on record - which is not the same as permission for Town of Northumberland. 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 Northumberland 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) 792-9179 before relying on any answer. Sources: Offsite / Aldo cost engine (costEngine.js + constants.js); zoning dataset (municipalData.js).