Fremont · ADU cost
What it costs to build an ADU in Fremont, NY
An 800 sq ft accessory dwelling unit in Fremont 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 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 Fremont maps 8 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 Fremont
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 Fremont 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 |
|---|---|---|---|---|
| Residential Recreation District | 0.92 ac | 60 / 25 / 50 ft | 40 ft | — |
| Residential District | 0.92 ac | 60 / 25 / 50 ft | 40 ft | — |
| Hamlet District | 0.69 ac | 50 / 25 / 40 ft | 40 ft | — |
| River Conservation District | 2.75 ac | 60 / 50 / 50 ft | 40 ft | — |
| Mountain Conservation District (Basket Sub-District) | 4.59 ac | 60 / 50 / 50 ft | 40 ft | — |
| Mountain Conservation District (Plateau Sub-District) | 2.75 ac | 60 / 50 / 50 ft | 40 ft | — |
| Anawanda Lake Conservation District | 2.75 ac | 60 / 50 / 50 ft | 35 ft | — |
| Muskoday-Tennanah Lake Conservation District | 4.59 ac | 60 / 50 / 50 ft | 35 ft | — |
Residential Recreation District - On an on-site well and septic system at a slope of 0 to 8% the minimum lot is 40,000 square feet, 150 feet wide and 150 feet deep, with a 60 foot front yard, 25 foot side yards, 60 feet for both sides, a 50 foot rear yard, 15% lot coverage and a 40 foot height limit.
- Slope sets the lot minimum here: 80,000 square feet at a slope of 8 to 15%, 120,000 square feet at 15 to 25%, and 200,000 square feet at 25% and above.
- The minimum lot area rises by 40,000 square feet where a seasonal high water table or bedrock lies 4 feet or less down, and by 80,000 square feet where either lies less than 2 feet down.
- On central sewage and water the minimum lot is 30,000 square feet, 125 feet wide and 125 feet deep, with a 50 foot front yard, 50 feet for both sides, a 40 foot rear yard and 25% lot coverage.
- A conservation subdivision is granted by the Planning Board with the plat, not by right. Yards drop to 35 feet front and 20 side and rear, on 40,000 square feet on-site or 20,000 on central.
- A two-family dwelling requires twice the minimum lot area, and a yard bordering a lake, stream or other water body is at least 100 feet deep.
- Every residential lot needs a front lot line at least 50 feet long. An unattached accessory structure sits 5 feet from a side or rear lot line, or 10 feet for a garage absent special use approval.
Residential District - On an on-site well and septic system the minimum lot is 40,000 square feet, 150 feet wide and 150 feet deep, with a 60 foot front yard, 25 foot side yards, 60 feet for both sides, a 50 foot rear yard, 25% lot coverage and a 40 foot height limit.
- On central sewage and water the minimum lot is 30,000 square feet, 125 feet wide and 125 feet deep, with a 50 foot front yard, 50 feet for both sides and a 40 foot rear yard.
- A conservation subdivision is granted by the Planning Board with the plat, not by right. Yards drop to 35 feet front and 20 side and rear, on 40,000 square feet on-site or 20,000 on central.
- A two-family dwelling requires twice the minimum lot area, and a yard bordering a lake, stream or other water body is at least 100 feet deep.
- Every residential lot needs a front lot line at least 50 feet long. An unattached accessory structure sits 5 feet from a side or rear lot line, or 10 feet for a garage absent special use approval.
Hamlet District - On an on-site well and septic system the minimum lot is 30,000 square feet, 125 feet wide and 125 feet deep, with a 50 foot front yard, 25 foot side yards, 50 feet for both sides, a 40 foot rear yard, 15% lot coverage and a 40 foot height limit.
- On central sewage with an on-site well the minimum lot is 20,000 square feet, 100 feet wide and 100 feet deep, with a 40 foot front yard, 20 foot side and rear yards and 25% lot coverage.
- On central sewage and water the minimum lot is 12,000 square feet, 100 feet wide and 100 feet deep, with a 40 foot front yard, 20 foot side and rear yards and 25% lot coverage.
- A conservation subdivision is granted by the Planning Board with the plat, not by right. Yards drop to 35 feet front and 20 side and rear, on 40,000 square feet on-site or 20,000 on central.
- That 40,000 square foot cluster floor is larger than the 30,000 square foot minimum this district sets, so cluster design lowers the lot minimum here only on central sewer and water.
- On a Tennanah Lake parcel with shoreline frontage, impervious surfaces in the waterfront yard may not exceed 15% of that yard, and the waterfront yard is at least 100 feet deep.
- Every residential lot needs a front lot line at least 50 feet long. An unattached accessory structure sits 5 feet from a side or rear lot line, or 10 feet for a garage absent special use approval.
River Conservation District - The minimum lot is 120,000 square feet whatever the water and sewage service, 150 feet wide and 150 feet deep, with a 60 foot front yard, 50 foot side yards, 100 feet for both sides, a 50 foot rear yard, 10% lot coverage and a 40 foot height limit.
- The town's conservation subdivision option does not reach this district, so lots here cannot be clustered on smaller parcels.
- A two-family dwelling requires twice the minimum lot area, and a yard bordering a lake, stream or other water body is at least 100 feet deep.
- Every residential lot needs a front lot line at least 50 feet long. An unattached accessory structure sits 5 feet from a side or rear lot line, or 10 feet for a garage absent special use approval.
Mountain Conservation District (Basket Sub-District) - The minimum lot is 200,000 square feet whatever the water and sewage service, 200 feet wide and 200 feet deep, with a 60 foot front yard, 50 foot side yards, 100 feet for both sides, a 50 foot rear yard, 5% lot coverage and a 40 foot height limit.
- A conservation subdivision is granted by the Planning Board with the plat, not by right. Yards drop to 35 feet front and 20 side and rear, on 40,000 square feet on-site or 20,000 on central.
- A two-family dwelling requires twice the minimum lot area, and a yard bordering a lake, stream or other water body is at least 100 feet deep.
- Every residential lot needs a front lot line at least 50 feet long. An unattached accessory structure sits 5 feet from a side or rear lot line, or 10 feet for a garage absent special use approval.
Mountain Conservation District (Plateau Sub-District) - The minimum lot is 120,000 square feet whatever the water and sewage service, 150 feet wide and 150 feet deep, with a 60 foot front yard, 50 foot side yards, 100 feet for both sides, a 50 foot rear yard, 5% lot coverage and a 40 foot height limit.
- A conservation subdivision is granted by the Planning Board with the plat, not by right. Yards drop to 35 feet front and 20 side and rear, on 40,000 square feet on-site or 20,000 on central.
- A two-family dwelling requires twice the minimum lot area, and a yard bordering a lake, stream or other water body is at least 100 feet deep.
- Every residential lot needs a front lot line at least 50 feet long. An unattached accessory structure sits 5 feet from a side or rear lot line, or 10 feet for a garage absent special use approval.
Anawanda Lake Conservation District - The minimum lot is 120,000 square feet whatever the water and sewage service, 200 feet wide and 200 feet deep, with a 60 foot front yard, 50 foot side yards, 100 feet for both sides, a 50 foot rear yard and a 35 foot height limit.
- Coverage is capped as an area rather than a percentage: 6,000 square feet on a lot under 1 acre, 7,500 square feet on 1 to 2 acres and 9,000 square feet on 2 to 5 acres.
- The same coverage cap is 10,000 square feet on 5 to 10 acres and 15,000 square feet on 10 acres and above.
- A conservation subdivision is granted by the Planning Board with the plat, not by right. Yards drop to 35 feet front and 20 side and rear, on 40,000 square feet on-site or 20,000 on central.
- Impervious surfaces inside a waterfront yard may not exceed 15% of that yard, and a yard bordering a lake, stream or other water body is at least 100 feet deep.
- A two-family dwelling requires twice the minimum lot area.
- Every residential lot needs a front lot line at least 50 feet long. An unattached accessory structure sits 5 feet from a side or rear lot line, or 10 feet for a garage absent special use approval.
Muskoday-Tennanah Lake Conservation District - The minimum lot is 200,000 square feet whatever the water and sewage service, 200 feet wide and 200 feet deep, with a 60 foot front yard, 50 foot side yards, 100 feet for both sides, a 50 foot rear yard and a 35 foot height limit.
- Coverage is capped as an area rather than a percentage: 6,000 square feet on a lot under 1 acre, 7,500 square feet on 1 to 2 acres and 9,000 square feet on 2 to 5 acres.
- The same coverage cap is 10,000 square feet on 5 to 10 acres and 15,000 square feet on 10 acres and above.
- A conservation subdivision is granted by the Planning Board with the plat, not by right. Yards drop to 35 feet front and 20 side and rear, on 40,000 square feet on-site or 20,000 on central.
- Impervious surfaces inside a waterfront yard may not exceed 15% of that yard, and a yard bordering a lake, stream or other water body is at least 100 feet deep.
- A two-family dwelling requires twice the minimum lot area.
- Every residential lot needs a front lot line at least 50 feet long. An unattached accessory structure sits 5 feet from a side or rear lot line, or 10 feet for a garage absent special use approval.
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. Fremont has not adopted a local short term rental permitting law, so no local permit requirement is confirmed for this parcel. Since no local rule is on the books, confirm with the building department before counting on renting short term. Separate question from whether you can build the unit.
- Zoning codefremontny.org/Section%20100%20Town%20Zoning%20Law%20(2016).pdf
- Building dept(845) 887-6605
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Building a full house instead?
A standard-finish house in Fremont runs $195–256/sq ft, about $350k–460k at 1,800 sq ft , plus roughly $6,658 for a conforming lot. See what it costs to build a house in Fremont.
ADU cost in nearby towns
All Sullivan County towns: Bethel · Callicoon · Cochecton · Delaware · Fallsburg · Forestburgh · Highland · Liberty · Lumberland · Mamakating · Neversink · Rockland · Thompson · Tusten · Bloomingburg (Village) · Jeffersonville (Village) · Liberty (Village) · Monticello (Village) · Woodridge (Village)
More on Fremont: Can you build an ADU here? · Zoning for new construction · Sullivan County build cost
ADU cost in Fremont: common questions
How much does it cost to build an ADU in Fremont, NY?
An 800 sq ft accessory dwelling unit in Town of Fremont 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 Fremont?
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 Fremont?
Town of Fremont has 8 districts. ADU data not yet available - verify with the building department at (845) 887-6605. Check the specific address with the free ADU checker before you spend money on design.
Can I rent an ADU in Fremont short term?
No local short-term-rental law on record - which is not the same as permission for Town of Fremont. 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 Town of Fremont 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) 887-6605 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.