Monticello · ADU cost
What it costs to build an ADU in Monticello, NY
An 800 sq ft accessory dwelling unit in Monticello runs roughly $190k–250k, or about $238–312/sq ft, and that per-square-foot figure sits deliberately above the $195–256/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 Monticello maps 5 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 Monticello
Standard finish, slab on grade, on a flat and clear part of the lot, general-contractor margin included. These are structure costs at Sullivan County pricing, before the service and septic work a second dwelling can trigger.
| Size | Type | $ / sq ft | Estimated total |
|---|---|---|---|
| 400 sq ft | Studio | $316–$414 | $125k–165k |
| 600 sq ft | One bedroom | $264–$346 | $160k–210k |
| 800 sq ft | One bedroom, larger | $238–$312 | $190k–250k |
| 1,000 sq ft | Two bedroom | $223–$292 | $225k–290k |
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–$10 | $7 | — |
| Foundation | $16–$22 | $16 | — |
| Framing | $24–$30 | $24 | — |
| Envelope - roof, siding, windows | $30–$39 | $30 | — |
| Plumbing | $26–$32 | $16 | 55% |
| Electrical | $18–$23 | $12 | 35% |
| HVAC | $22–$27 | $14 | 45% |
| Insulation | $7–$9 | $7 | — |
| Interior finishes | $31–$41 | $26 | 15% |
| Millwork & cabinetry | $18–$26 | $10 | 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 Monticello 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 |
|---|---|---|---|---|
| Residence (One-Family) | 0.23 ac | 30 / 10 / 30 ft | 30 ft | No |
| Residence (One- and Two-Family) | 0.17 ac | 30 / 10 / 25 ft | 30 ft | No |
| Residence (Multifamily) | 0.17 ac | 30 / 10 / 25 ft | 30 ft | No |
| General Business | 0.23 ac | 30 / 10 / 20 ft | 35 ft | No |
| Core Business | 0.057 ac | 0 / 0 / 20 ft | 35 ft | No |
Residence (One-Family) - A home here needs 10,000 square feet, 0.2296 acre, on a lot 100 feet wide, set back 30 feet at the front, 30 feet at the rear and 10 feet on one side, with 30 feet for both sides together. Buildings cover up to 20% of the lot and reach 30 feet.
- A one-family dwelling must hold at least 768 square feet of living space under § 280-21, and it is the only principal use permitted outright.
- A place of worship needs a special use permit on 40,000 square feet, 150 feet of width, 40 feet front, 20 feet one side, 50 feet both sides, 35 feet rear and 35 feet of height.
- Home occupations, schools, colleges, libraries, museums, parks, playgrounds and golf courses need a special use permit on 10,000 square feet, with 100 feet of width and 30 foot yards.
- Places of worship include parish houses, seminaries, cemeteries, convents and dormitories.
Residence (One- and Two-Family) - A home here needs 7,500 square feet, 0.1722 acre, on a lot 75 feet wide, set back 30 feet at the front, 25 feet at the rear and 10 feet on one side, with 25 feet for both sides together. Buildings cover up to 25% of the lot and reach 30 feet.
- One-family and two-family dwellings are both permitted outright and share those figures.
- A one-family dwelling must hold at least 768 square feet of living space, and a two-family dwelling 1,500 square feet, under § 280-21.
- A place of worship needs a special use permit on 40,000 square feet, 150 feet of width, 40 feet front, 20 feet one side, 50 feet both sides, 35 feet rear, 35 feet of height and 20% coverage.
- Home occupations, bed-and-breakfasts, schools, colleges, libraries, museums, parks and golf courses need a special use permit on 10,000 square feet, with 100 feet of width and 30 foot yards.
- Places of worship include parish houses, seminaries, cemeteries, convents and dormitories.
Residence (Multifamily) - A home here needs 7,500 square feet, 0.1722 acre, on a lot 75 feet wide, set back 30 feet at the front, 25 feet at the rear and 10 feet on one side, with 25 feet for both sides together. Buildings cover up to 25% of the lot and reach 30 feet.
- One-family and two-family dwellings are the uses permitted outright, holding at least 768 and 1,500 square feet of living space under § 280-21.
- Townhouses need a special use permit on 2,000 square feet per dwelling and not more than 8 dwellings per acre of gross lot area, on lots 20 feet wide.
- A townhouse lot takes a 30 foot front yard, a 30 foot rear yard, 40% coverage and 35 feet of height, with a 15 foot side yard for end dwellings only.
- Apartments 35 feet and under need a special use permit on 10,000 square feet, 0.2296 acre, 150 feet of width, 40 feet front, 20 feet one side, 50 feet both sides, 35 feet rear and 20% coverage.
- Apartments over 35 feet need a special use permit on 200,000 square feet, 400 feet of width, a 50 foot front yard, 10% coverage and 75 feet of height.
- For those taller buildings the distance to any side or rear lot line is 1 1/2 times the height of the principal buildings, and does not apply to accessory buildings or parking.
General Business - A store, office, restaurant or funeral home here needs 10,000 square feet, 0.2296 acre, on a lot 90 feet wide, set back 30 feet at the front, 20 feet at the rear and 10 feet on one side, with 30 feet for both sides, at 40% coverage and 35 feet.
- One-family and two-family dwellings are permitted outright on the same figures, holding at least 768 and 1,500 square feet of living space under § 280-21.
- Townhouses need a special use permit on 2,000 square feet per dwelling and not more than 8 dwellings per acre of gross lot area, on lots 20 feet wide, with 30 foot front and rear yards.
- No side yard is required for a townhouse except 15 feet for end dwellings, and the row carries 40% coverage and 35 feet of height.
- Apartments 35 feet and under need a special use permit on 10,000 square feet, 150 feet of width, 40 feet front, 20 feet one side, 50 feet both sides, 35 feet rear and 20% coverage.
- Apartments over 35 feet need a special use permit on 200,000 square feet, 400 feet of width, a 50 foot front yard, 10% coverage and 75 feet of height.
- Assisted living under § 280-40.3 needs a special use permit on 4,000 square feet per unit on a vacant lot and 900 square feet per unit in an existing building.
Core Business - A store, office, restaurant or funeral home here needs 2,500 square feet, 0.0574 acre, on a lot 25 feet wide, with a 20 foot rear yard, no side yard required, 40% coverage and 35 feet.
- Where a side yard is provided it must be at least 12 feet.
- Residential use is permitted under § 280-40.5 on the upper stories, in studios, one-bedroom and two-bedroom dwellings, with no unit of 3 or more bedrooms.
- A studio takes 550 square feet, a one-bedroom unit 650 square feet and a two-bedroom unit 750 square feet under § 280-40.5.
- A motel or hotel under § 280-15 needs a special use permit on 7,500 square feet plus 1,500 per unit, 150 feet of width, 30 feet front, 25 feet one side, 50 feet both sides and 75 feet of height.
- A place of worship or a hospital needs a special use permit on 40,000 square feet and 150 feet of width, with a 40 foot front yard and 35 feet of height.
- Commercial recreation needs a special use permit on 10,000 square feet, 90 feet of width, 30 feet front, 10 feet one side, 30 feet both sides, 20 feet rear, 30% coverage and 35 feet.
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 NYSEG 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. As of June 2026 the Village of Monticello has no local law specific to short-term rentals. That is not the same as permission, so confirm with the building department before counting on renting short term. Separate question from whether you can build the unit.
- Zoning codeecode360.com/MO0528
- Building dept(845) 794-2429
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Building a full house instead?
A standard-finish house in Monticello runs $195–256/sq ft, about $350k–460k at 1,800 sq ft , plus roughly $9,543 for a conforming lot. See what it costs to build a house in Monticello.
ADU cost in nearby towns
All Sullivan County towns: Bethel · Callicoon · Cochecton · Delaware · Fallsburg · Forestburgh · Fremont · Highland · Liberty · Lumberland · Mamakating · Neversink · Rockland · Thompson · Tusten · Bloomingburg (Village) · Jeffersonville (Village) · Liberty (Village) · Woodridge (Village)
More on Monticello: Can you build an ADU here? · Zoning for new construction · Sullivan County build cost
ADU cost in Monticello: common questions
How much does it cost to build an ADU in Monticello, NY?
An 800 sq ft accessory dwelling unit in Village of Monticello runs roughly $190k–250k at a standard finish, general-contractor margin included. A 400 sq ft studio runs about $125k–165k. 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 Monticello?
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 $238–312/sq ft against $195–256/sq ft for a full house, even though it is the same trades doing the same work.
Are ADUs allowed in Monticello?
Village of Monticello has 5 districts. All districts prohibit ADUs. Check the specific address with the free ADU checker or confirm with the building department at (845) 794-2429 before you spend money on design.
Can I rent an ADU in Monticello short term?
No local short-term-rental law on record - which is not the same as permission for Village of Monticello. 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 Sullivan 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 Monticello vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-10-07; verify with the building department at (845) 794-2429 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.