Rush · ADU cost
What it costs to build an ADU in Rush, NY
An 800 sq ft accessory dwelling unit in Rush 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 Rush maps 6 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 Rush
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 Rush 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 20 | 0.46 ac | 100 / 15 / 25 ft | 35 ft | Special permit |
| Residential 30 | 0.69 ac | 100 / 25 / 25 ft | 35 ft | Special permit |
| Rural Residential 5 | 5 ac | 100 / 50 / 50 ft | 35 ft | Special permit |
| Residential Multiple Dwelling | 2 ac | 100 / 25 / 25 ft | 35 ft | No |
| Residential Mobile Home | 5 ac | 100 / 25 / 25 ft | 35 ft | No |
| Residential Townhouse | 1 ac | 100 / 25 / 25 ft | 35 ft | No |
Residential 20 - The 100 ft front setback is measured from the highway center line, not the front property line, so on a sixty-foot right-of-way it takes 30 ft less of the lot than the figure suggests. A lot on a state or county road owes 110 ft.
- The 50% cap counts buildings plus hardscape such as the drive, walks and patio; the 25% cap counts buildings only.
- A 50 ft minimum front lot line applies in addition to the lot width.
- Accessory structures may come no nearer to the highway or a lot line than the main structure may.
- An undersized pre-existing lot between 14,000 and 15,999 sq ft needs 85 ft of width and a 10 ft side setback; between 16,000 and 17,999, 90 ft and 12 ft; between 18,000 and 19,999, 95 ft and 14 ft.
- Minimum gross floor area is 1,000 sq ft per unit for a townhouse.
Residential 30 - The 100 ft front setback is measured from the highway center line, not the front property line, so on a sixty-foot right-of-way it takes 30 ft less of the lot than the figure suggests. A lot on a state or county road owes 110 ft.
- A townhouse takes a minimum gross floor area of 1,000 sq ft per unit rather than the 1,200 sq ft a detached house must reach; the lot, width, depth, setbacks and coverage are unchanged.
- The 50% cap counts buildings plus hardscape such as the drive, walks and patio; the 25% cap counts buildings only.
- A 50 ft minimum front lot line applies in addition to the lot width.
- Accessory structures may come no nearer to the highway or a lot line than the main structure may.
- An undersized pre-existing lot between 21,000 and 23,999 sq ft needs 125 ft of width and a 16 ft side setback; between 24,000 and 26,999, 135 ft and 20 ft; between 27,000 and 29,999, 145 ft and 24 ft.
Rural Residential 5 - The 100 ft front setback is measured from the highway center line, not the front property line, so on a sixty-foot right-of-way it takes 30 ft less of the lot than the figure suggests. A lot on a state or county road owes 110 ft.
- The 50% cap counts buildings plus hardscape such as the drive, walks and patio; the 25% cap counts buildings only.
- A 50 ft minimum front lot line applies in addition to the lot width.
- Accessory structures may come no nearer to the highway or a lot line than the main structure may.
- The undersized-lot relief in § 120-17 covers R-20 and R-30 only, not this district.
Residential Multiple Dwelling - The 2 acres shown is the minimum size of the whole development parcel, not the land one dwelling needs, and the unit count is set by 5,500 sq ft per dwelling unit under § 120-17.
- The 100 ft front setback is measured from the highway center line, not the front property line, so on a sixty-foot right-of-way it takes 30 ft less of the lot than the figure suggests.
- A lot on a state or county road owes a 110 ft front setback.
- The 50% cap counts buildings plus hardscape such as the drive, walks and patio; the 25% cap counts buildings only.
- A 50 ft minimum front lot line applies in addition to the lot width.
- Accessory structures may come no nearer to the highway or a lot line than the main structure may.
- Minimum gross floor area rises to 1,000 sq ft per unit for a townhouse.
Residential Mobile Home - The 5 acres shown is the minimum size of the whole development, and the unit count is set by 10,000 sq ft per dwelling unit under § 120-17. The 60 ft width, 100 ft depth and 35 ft minimum front lot line describe an individual pad, not the site.
- The 100 ft front setback is measured from the highway center line, not the front property line, so on a sixty-foot right-of-way it takes 30 ft less of the lot than the figure suggests.
- A lot on a state or county road owes a 110 ft front setback.
- The 50% cap counts buildings plus hardscape such as the drive, walks and patio; the 25% cap counts buildings only.
- Accessory structures may come no nearer to the highway or a lot line than the main structure may.
Residential Townhouse - The 1 acre shown is the minimum size of the whole development, and the unit count is set by 10,000 sq ft per dwelling unit under § 120-17. Side and rear setbacks apply to clusters, not units: 25 ft from a cluster to a property line and 50 ft between clusters.
- The zero width, depth and front lot line are the stated standard: an individual townhouse lot has no shape requirement because the development is regulated as a whole.
- The 25 ft rear setback is measured from the property line of the townhouse development.
- The 100 ft front setback is measured from the highway center line, not the front property line, so on a sixty-foot right-of-way it takes 30 ft less of the lot than the figure suggests.
- A lot on a state or county road owes a 110 ft front setback.
- The 50% cap counts buildings plus hardscape such as the drive, walks and patio; the 25% cap counts buildings only.
- Accessory structures may come no nearer to the highway or a lot line than the main structure may.
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 rentalsNo local short-term-rental law on record - which is not the same as permission. Rush has no local short-term rental law. That is not permission: the zoning code prohibits any use its closed use list does not name, so confirm with Code Enforcement before counting on a short-term rental. Separate question from whether you can build the unit.
- Zoning codeecode360.com/11861311
- Building dept(585) 533-1312
Sizing up a specific parcel in Rush?
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 Rush runs $204–268/sq ft, about $370k–480k at 1,800 sq ft , plus roughly $7,736 for a conforming lot. See what it costs to build a house in Rush.
ADU cost in nearby towns
All Monroe County towns: Rochester (City) · Brighton · Chili · Clarkson · Gates · Greece · Hamlin · Henrietta · Irondequoit · Mendon · Ogden · Parma · Penfield · Perinton · Pittsford · Riga · 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 Rush: Can you build an ADU here? · Zoning for new construction · Monroe County build cost
ADU cost in Rush: common questions
How much does it cost to build an ADU in Rush, NY?
An 800 sq ft accessory dwelling unit in Town of Rush 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 Rush?
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 Rush?
Town of Rush has 6 districts. 3 districts prohibit ADUs, 3 require a special-use permit. Check the specific address with the free ADU checker or confirm with the building department at (585) 533-1312 before you spend money on design.
Can I rent an ADU in Rush short term?
No local short-term-rental law on record - which is not the same as permission for Town of Rush. 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 Rush 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) 533-1312 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.