Perinton · ADU cost
What it costs to build an ADU in Perinton, NY
An 800 sq ft accessory dwelling unit in Perinton 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 Perinton maps 5 districts that treat accessory units differently from one another, so read the table below as a starting point rather than a verdict.
Check a specific parcel for an ADU in Aldo, free →
ADU cost by size in Perinton
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 Perinton 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 |
|---|---|---|---|---|
| Class AA Residential | 0.46 ac | 70 / 15 / 15 ft | 40 ft | No |
| Class A Residential | 0.41 ac | 70 / 12 / 15 ft | 40 ft | No |
| Class B Residential | 0.33 ac | 50 / 12 / 15 ft | 40 ft | No |
| Class C Residential | 0.33 ac | 50 / 12 / 15 ft | 40 ft | No |
| Apartment District | 0.34 ac | 70 / 40 / 40 ft | 40 ft | No |
Class AA Residential - A corner lot takes a larger lot: 30,000 sq ft on 150 ft of width, and it must hold the full front setback from each street or highway rather than a side yard. A single-family dwelling must also include a two-car private garage as a condition of the use.
- Minimum ground area of the main structure is 1,400 sq ft for a one-storey building, 1,200 sq ft for a one-and-a-half-storey and 1,000 sq ft for a two- or two-and-a-half-storey.
- Under § 208-34A(1), the Planning Board may permit townhouses in an AA, A, B or C residential subdivision of at least 40 developable acres.
- Townhouses may occupy no more than 10% of the developable area, and the application must be made with the pre-preliminary subdivision application.
- Townhouses must be in harmony with and complementary to the single-family houses proposed, and must meet the garage requirement of the district they sit in.
- The lot minimum in AA is a single figure that does not change with sewer service.
Class A Residential - The figures shown apply to lots served by public sewer. A corner lot must be larger: 27,000 sq ft on 135 ft of width, and it has to meet the full front setback from each street or highway rather than a side yard.
- A lot not served by sanitary sewers takes 20,000 sq ft on 100 ft of width, against 18,000 sq ft on 90 ft where sewers are available, and a corner lot 30,000 sq ft on 150 ft.
- Townhouses may be permitted by the Planning Board under § 208-34A(1) only in an AA, A, B or C residential subdivision of at least 40 developable acres, on no more than 10% of the developable area.
- A townhouse application must be made with the pre-preliminary subdivision application, be complementary to the single-family houses proposed, and meet the district's garage requirement.
- A single-family dwelling must have a two-car private garage.
- Minimum ground area of the main structure is 1,200 sq ft for a one-storey building, 1,000 sq ft for a one-and-a-half-storey and 850 sq ft for a two- or two-and-a-half-storey.
Class B Residential - The figures shown apply to a sewered single-family lot. This district publishes four sets of lot standards, crossing sewered against unsewered and single-family against two-family, and an unsewered lot owes a 15 ft side yard rather than 12 ft.
- An unsewered lot takes 20,000 sq ft on 100 ft of width, nearly 40% more than the 14,400 sq ft a sewered lot needs, with a 15 ft side setback; a corner lot takes 22,750 sq ft on 130 ft.
- A two-family needs 17,600 sq ft (0.404 acres) on 110 ft sewered or 21,875 sq ft (0.5022 acres) on 125 ft unsewered; corner lots are 20,800 sq ft on 130 ft and 26,250 sq ft on 150 ft.
- A corner lot takes more land: 19,200 sq ft on 120 ft of width, and its setback from each street or highway is the full front setback rather than a side yard.
- Minimum ground area runs 1,000 / 850 / 750 sq ft for a single-family dwelling, and for a two-family 1,800 sq ft one-storey, 1,300 one-and-a-half-storey and 1,100 two-storey.
- A semidetached dwelling may have one zero-foot side yard; an agricultural structure takes 140 ft front, 30 ft side and 50 ft rear; a two-family hearing is noticed to owners within 500 ft.
- Under § 208-34A(1) the Planning Board may permit townhouses in an AA, A, B or C subdivision of at least 40 developable acres, on no more than 10% of it, with the pre-preliminary application.
Class C Residential - The figures shown apply to a sewered single-family lot. This district publishes four lot rows, crossing sewered against unsewered and single-family against two-family, and an unsewered lot owes a 15 ft side yard rather than 12 ft.
- An unsewered lot takes 20,000 sq ft on 100 ft of width, nearly 40% more than the 14,400 sq ft a sewered lot needs, with a 15 ft side setback; a corner lot takes 22,750 sq ft on 130 ft.
- A two-family needs 17,600 sq ft (0.404 acres) on 110 ft sewered or 21,875 sq ft (0.5022 acres) on 125 ft unsewered; corner lots are 20,800 sq ft on 130 ft and 26,250 sq ft on 150 ft.
- A corner lot takes a larger lot, 19,200 sq ft on 120 ft of width, and its setback from each street or highway is the full front setback rather than a side yard.
- Minimum ground area runs 900 / 800 / 650 sq ft for a single-family dwelling, and for a two-family 1,800 sq ft one-storey, 1,300 one-and-a-half-storey and 1,100 two-storey.
- A semidetached dwelling may have one zero-foot side yard, and a two-family hearing is noticed to every owner within 500 ft at least a week and no more than three weeks before it.
- Under § 208-34A(1) the Planning Board may permit townhouses in an AA, A, B or C subdivision of at least 40 developable acres, on no more than 10% of it, complementary to the houses proposed.
Apartment District - Land area runs 15,000 sq ft for the first dwelling unit in each apartment building plus 3,000 sq ft for each additional unit. An apartment building must hold at least four units and no more than twelve, so a three-unit building is not permitted.
- The 30% building coverage is measured against the developable project area, not the whole parcel.
- The 40 ft side and rear figure is measured from all property lines.
- Minimum unit sizes are 550 sq ft for an efficiency, 675 for a one-bedroom, 800 for a two-bedroom and 950 for a three-bedroom; efficiencies may be no more than 25% of the units.
- Buildings in a group must stand 20 ft apart, or the height of the highest adjacent building if greater. No exterior wall may run more than 100 ft without a lateral offset of at least eight feet.
- A building or group of more than 12 units needs direct access to a county or state highway by a private driveway or a road dedicated to the Town by the developer.
- Open parking may not sit in a front or side yard.
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. Short-term rentals are allowed only in the Restricted Business, Commercial and Mixed Use districts, with a building permit, certificate of occupancy and operating permit. They are prohibited in residential, Apartment, Townhouse, Industrial and Planned Development districts. Separate question from whether you can build the unit.
- Zoning codeecode360.com/6741096
- Building dept(585) 223-0770
Sizing up a specific parcel in Perinton?
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 Perinton runs $204–268/sq ft, about $370k–480k at 1,800 sq ft , plus roughly $5,260 for a conforming lot. See what it costs to build a house in Perinton.
ADU cost in nearby towns
All Monroe County towns: Rochester (City) · Brighton · Chili · Clarkson · Gates · Greece · Hamlin · Henrietta · Irondequoit · Mendon · Ogden · Parma · Penfield · 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 Perinton: Can you build an ADU here? · Zoning for new construction · Monroe County build cost
ADU cost in Perinton: common questions
How much does it cost to build an ADU in Perinton, NY?
An 800 sq ft accessory dwelling unit in Town of Perinton 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 Perinton?
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 Perinton?
Town of Perinton has 5 districts. All districts prohibit ADUs. Check the specific address with the free ADU checker or confirm with the building department at (585) 223-0770 before you spend money on design.
Can I rent an ADU in Perinton short term?
Short-term rentals allowed with local rules for Town of Perinton. 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 Perinton vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-08-07; verify with the building department at (585) 223-0770 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.