Clarkson · ADU cost
What it costs to build an ADU in Clarkson, NY
An 800 sq ft accessory dwelling unit in Clarkson 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 Clarkson maps 3 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 Clarkson
Standard finish, slab on grade, on a flat and clear part of the lot, general-contractor margin included. These are structure costs at Monroe 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 Clarkson 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 Residential | 2 ac | 40 / 25 / 30 ft | 35 ft | Special permit |
| Residential Suburban — 20,000 sq ft | 0.46 ac | 40 / 10 / 30 ft | 35 ft | Special permit |
| Residential Suburban — 10,000 sq ft | 0.23 ac | 40 / 10 / 30 ft | 35 ft | Special permit |
Agricultural Residential - A lot fronting a major road owes a 75 ft front setback. A two-family dwelling takes the same dimensions as a single-family, so a second unit needs no extra land, but it is a specially permitted use rather than a right.
- Agricultural operations need 5 acres and 250 ft of width, with a 100 ft front yard, 35 ft sides and a 60 ft rear.
- The height cap does not apply to barns, silos, water towers or tanks, windmills or other farm buildings on active farmland.
- Keeping farm animals needs 5 acres, keeping chickens 3 acres and keeping bees 2 acres, each with 30 ft side and rear setbacks.
- The accessory dwelling unit and the short-term rental are also specially permitted uses.
- Accessory structures take 15 ft side and rear yards and a 20 ft height cap.
Residential Suburban — 20,000 sq ft - A two-family dwelling takes the same 20,000 sq ft as a single-family, and a detached accessory dwelling unit is available on top under § 140-23.4, so a minimum lot can reach three units. Both the two-family and the accessory unit need their own special permit.
- A lot fronting a major road owes a 75 ft front setback.
- Any structure other than a dwelling or attached garage owes a 10 ft rear setback, and accessory structures take 10 ft side yards and a 20 ft height cap.
- A public park or playground, a religious or educational institution, and an animal hospital or grooming shop each need a full acre; a kennel needs an acre with 30 ft side and rear yards.
- Agricultural operations need 5 acres on 200 ft of width, and a golf course needs 50 acres.
- Keeping chickens needs 3 acres and keeping bees 2 acres, each with 30 ft side and rear yards.
Residential Suburban — 10,000 sq ft - A two-family dwelling takes the same 10,000 sq ft and 75 ft as a single-family, but only as new construction: converting an existing house into two units is prohibited at any lot size.
- This is the only district in the town reaching multifamily, in two tiers: up to a 4-unit dwelling takes 20,000 sq ft on 100 ft of width, and over four units a full acre on the same 100 ft.
- Both tiers are specially permitted, governed additionally by § 140-23.17, and both raise the height cap to 40 ft against the 35 ft for one- and two-family forms.
- Every nonresidential use takes 20,000 sq ft on 100 ft of width; a short-term rental is the exception on setbacks, taking a 25 ft front yard rather than 40 ft, on 75 ft of width.
- A lot fronting a major road owes a 75 ft front setback.
- Any structure other than a dwelling or attached garage owes a 10 ft rear setback, and accessory structures take 10 ft side yards and a 20 ft height cap.
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 RG&E 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 rentalsShort-term rentals allowed with local rules. Clarkson regulates short-term rentals in § 140-23.21 of its zoning code, separately from bed-and-breakfasts. Whether a permit or registration, an occupancy cap or an owner-occupancy rule applies is not confirmed, so confirm with the building department before counting on the use. Separate question from whether you can build the unit.
- Zoning codeecode360.com/48554267
- Building dept(585) 637-1145
Sizing up a specific parcel in Clarkson?
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 Clarkson runs $204–268/sq ft, about $370k–480k at 1,800 sq ft , plus roughly $865 for a conforming lot. See what it costs to build a house in Clarkson.
ADU cost in nearby towns
All Monroe County towns: Rochester (City) · Brighton · Chili · Gates · Greece · Hamlin · Henrietta · Irondequoit · Mendon · Ogden · Parma · Penfield · Perinton · Pittsford · Riga · Rush · Sweden · Webster · Wheatland · East Rochester (Village) · Brockport (Village) · Churchville (Village) · Fairport (Village) · Hilton (Village) · Honeoye Falls (Village) · Pittsford (Village) · Scottsville (Village) · Spencerport (Village) · Webster (Village)
More on Clarkson: Can you build an ADU here? · Zoning for new construction · Monroe County build cost
ADU cost in Clarkson: common questions
How much does it cost to build an ADU in Clarkson, NY?
An 800 sq ft accessory dwelling unit in Town of Clarkson 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 Clarkson?
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 Clarkson?
Town of Clarkson has 3 districts. All districts allow ADUs with a special-use permit. Check the specific address with the free ADU checker or confirm with the building department at (585) 637-1145 before you spend money on design.
Can I rent an ADU in Clarkson short term?
Short-term rentals allowed with local rules for Town of Clarkson. 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 Monroe 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 Clarkson vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-08-13; verify with the building department at (585) 637-1145 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.