East Rochester · ADU cost
What it costs to build an ADU in East Rochester, NY
An 800 sq ft accessory dwelling unit in East Rochester 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 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 Town/Village of East Rochester 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 East Rochester
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 East Rochester 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 |
|---|---|---|---|---|
| R-1-70 Residential District | 0.16 ac | 25 / 5 / 20 ft | 35 ft | No |
| R-1-48 Residential District | 0.11 ac | 20 / 5 / 15 ft | 35 ft | No |
| TR Townhouse Residential District | 0.11 ac | 20 / 5 / 15 ft | 35 ft | No |
R-1-70 Residential District - A minimum green space of 30% applies alongside the coverage cap and binds independently of it, and at least half of the required green space must be in the front yard.
- Public and semipublic uses take 20,000 sq ft on 100 ft of width, with 50 ft front, 30 ft rear and side yards of 15 ft one side and 30 ft both, at 25% coverage, on a special use permit.
- All measurements are made from the street or right-of-way line.
- Accessory buildings take 5 ft at the rear and 5 ft at the side.
- Accessory buildings must stand clear of any other building by 10 ft up to 64 sq ft, 12 ft above 64 and under 121 sq ft, and 15 ft at 121 sq ft and above.
- The minimum ground floor area shown is for a one-storey dwelling. A storey-and-a-half needs 900 sq ft and a two-storey 800 sq ft.
R-1-48 Residential District - The side yard is keyed to storeys: 5 ft for a two-storey dwelling and 4 ft for a one-storey, on both sides. Adding a second storey to a one-storey house increases its required side yard and can put a lawfully built dwelling out of compliance.
- Public and semipublic uses take 20,000 sq ft on 100 ft of width, with 50 ft front, 30 ft rear and side yards of 15 ft one side and 30 ft both, at 25% coverage, on a special use permit.
- A minimum green space of 30% applies alongside the coverage cap and binds independently of it, with at least half of the required green space in the front yard.
- All measurements are made from the street or right-of-way line.
- Accessory buildings take 3 ft at the rear and 3 ft at the side.
- The minimum ground floor area shown is for a one-storey dwelling. A storey-and-a-half needs 720 sq ft and a two-storey 624 sq ft.
TR Townhouse Residential District - The figures shown are the single- and two-family standard, and townhouse and multifamily development follows a completely different standard. § 193-55E(2) sets a one-acre minimum tract for land rezoned to TR.
- Townhouses are permitted by right and an apartment house by special permit, on the same dimensions: no flat lot minimum, 2,500 sq ft per dwelling unit on 80 ft of width, roughly 17 units to the acre.
- Front and side yards are keyed to height: 30 ft or the building height at the front and 15 ft or half the height at each side, giving 50 ft and 25 ft at the 50 ft cap, with 50% coverage.
- Public and semipublic uses take 20,000 sq ft on 100 ft of width, with 50 ft front, 30 ft rear and side yards of 15 ft one side and 30 ft both, at 25% coverage, on a special use permit.
- For single- and two-family dwellings the side yard is 5 ft for a two-storey and 4 ft for a one-storey on both sides, and all measurements are made from the street line.
- A minimum green space of 20% applies alongside the coverage cap and binds independently of it, with at least half of the required green space in the front yard.
- § 193-55E sets minimum living space per unit: 500 sq ft for a studio, 600 for one bedroom, 800 for two bedrooms and 950 for three bedrooms.
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. East Rochester has no local short-term rental law, and that is not the same as permission. Confirm with the Building Inspector whether a short-term rental is a permitted zoning use before counting on it. Separate question from whether you can build the unit.
- Zoning codeecode360.com/10126413
- Building dept(585) 586-3553
Sizing up a specific parcel in East Rochester?
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 East Rochester runs $204–268/sq ft, about $370k–480k at 1,800 sq ft , plus roughly $22,407 for a conforming lot. See what it costs to build a house in East Rochester.
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 · Rush · Sweden · Webster · Wheatland · Brockport (Village) · Churchville (Village) · Fairport (Village) · Hilton (Village) · Honeoye Falls (Village) · Pittsford (Village) · Scottsville (Village) · Spencerport (Village) · Webster (Village)
More on East Rochester: Can you build an ADU here? · Zoning for new construction · Monroe County build cost
ADU cost in East Rochester: common questions
How much does it cost to build an ADU in East Rochester, NY?
An 800 sq ft accessory dwelling unit in Town/Village of East Rochester 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 East Rochester?
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 East Rochester?
Town/Village of East Rochester has 3 districts. All districts prohibit ADUs. Check the specific address with the free ADU checker or confirm with the building department at (585) 586-3553 before you spend money on design.
Can I rent an ADU in East Rochester short term?
No local short-term-rental law on record - which is not the same as permission for Town/Village of East Rochester. 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/Village of East Rochester vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-08-14; verify with the building department at (585) 586-3553 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.