Chili · ADU cost
What it costs to build an ADU in Chili, NY
An 800 sq ft accessory dwelling unit in Chili 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 Chili maps 9 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 Chili
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 Chili 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 |
|---|---|---|---|---|
| Single-Family Residential | 0.14 ac | 40 / 8 / 25 ft | 35 ft | No |
| Residential Single-Family | 0.28 ac | 60 / 10 / 30 ft | 35 ft | No |
| Residential Single-Family | 0.34 ac | 60 / 10 / 40 ft | 35 ft | No |
| Residential Single-Family | 0.46 ac | 60 / 10 / 60 ft | 35 ft | No |
| Residential Multiple-Family | 0.83 ac | 60 / 40 / 30 ft | 35 ft | No |
| Rural Agricultural | 1 ac | 100 / 30 / 50 ft | 35 ft | No |
| Rural Agricultural | 10 ac | 100 / 50 / 50 ft | 35 ft | No |
| Agricultural Conservation | 2 ac | 75 / 50 / 50 ft | 35 ft | No |
| Planned Residential Development | 50 ac | — | — | No |
Single-Family Residential - The 50 ft width and 40 ft front setback shown apply on ordinary roads. On a lot fronting one of the major highways listed in § 500-59D, the width rises to 60 ft and the front setback to 75 ft.
Residential Single-Family, Residential Single-Family, Residential Single-Family - The 60 ft front setback shown applies on ordinary roads. A lot fronting one of the major highways listed in § 500-59D needs a 75 ft front setback.
Residential Multiple-Family - The 36,000 sq ft minimum is a minimum site, and yield comes from density: 8 units per gross acre where units are built as a linear series with no common hallways or entrances. No building may hold more than 12 units, and no more than six may be in a row.
- On a lot fronting one of the major highways listed in § 500-59D, the front setback is 75 ft.
- A building must also stand 40 ft from the street line of any interior project road, and side yards on townhouse party-wall lot lines may be zero.
- Minimum unit size is 550 sq ft for an efficiency, 700 for a one-bedroom and 850 for a two-bedroom, plus 150 sq ft for each additional bedroom.
- No more than 10% of all units may have three bedrooms or more.
- Coverage is calculated on the total project area, and all construction needs Planning Board site plan approval.
- Single-family dwellings and duplexes need a special permit; apartment houses, condominiums and cooperatives are permitted outright.
Rural Agricultural - The district states no maximum lot coverage.
Rural Agricultural - The 500 ft width is what shapes an RA-10 parcel: ten acres laid out with less than 500 ft of frontage does not comply, however much area it holds.
- The district states no maximum lot coverage.
Agricultural Conservation - The 5% coverage cap is the lowest in the town, and on a two-acre lot it allows about 4,350 sq ft of building footprint.
- A farm takes a separate column and five times the land: 10 acres on 500 ft of width with a 100 ft front setback, and its coverage allowance is five times as generous at 25%.
- The side and rear setbacks are the same 50 ft in both columns.
- The figures shown are the standards for a single-family dwelling.
Planned Residential Development - The 50 acres shown is the tract a proposal needs to qualify, not a lot minimum: it must contain at least 50 contiguous acres. Setbacks, height and coverage are set by the Planning Board at site plan review under Article V.
- On the serviced part an individual residential lot has both a minimum and a maximum: not less than 10,000 sq ft and not more than 20,000 sq ft, so a larger lot is as non-conforming as a smaller one.
- Multifamily units on the serviced part are capped at 10 units per acre.
- On the part not served by public sewer and water the minimum residential lot is 5 acres, increased as needed for the separation the County Department of Health requires around a well.
- There only agriculture and related residential uses, single-family residences and a customary home occupation are permitted outright.
- The application must be filed by the owner, lessee or all joint owners of the whole tract, and the approved plan binds every one of them.
- Manufactured homes are the one residential form excluded.
Size limits on record in Chili
Where the code states a size cap, it decides which row of the cost table above actually applies to you. These are the caps recorded for Chili:
- Single-Family ResidentialEach unit of a two-family dwelling must meet the single-family floor area standards: 850 sq ft for one bedroom, 1,000 for two, 1,150 for three, 1,300 for four (§ 500-101).
- Residential Single-FamilyEach unit of a two-family dwelling must meet the single-family floor area standards: 850 sq ft for one bedroom, 1,000 for two, 1,150 for three, 1,300 for four (§ 500-101).
- Residential Single-FamilyEach unit of a two-family dwelling must meet the single-family floor area standards: 850 sq ft for one bedroom, 1,000 for two, 1,150 for three, 1,300 for four (§ 500-101).
- Residential Single-FamilyEach unit of a two-family dwelling must meet the single-family floor area standards: 850 sq ft for one bedroom, 1,000 for two, 1,150 for three, 1,300 for four (§ 500-101).
- Residential Multiple-FamilyEach unit of a two-family dwelling must meet the single-family floor area standards: 850 sq ft for one bedroom, 1,000 for two, 1,150 for three, 1,300 for four (§ 500-101).
- Rural AgriculturalEach unit of a two-family dwelling must meet the single-family floor area standards: 850 sq ft for one bedroom, 1,000 for two, 1,150 for three, 1,300 for four (§ 500-101).
- Rural AgriculturalEach unit of a two-family dwelling must meet the single-family floor area standards: 850 sq ft for one bedroom, 1,000 for two, 1,150 for three, 1,300 for four (§ 500-101).
- Agricultural ConservationEach unit of a two-family dwelling must meet the single-family floor area standards: 850 sq ft for one bedroom, 1,000 for two, 1,150 for three, 1,300 for four (§ 500-101).
- Planned Residential DevelopmentEach unit of a two-family dwelling must meet the single-family floor area standards: 850 sq ft for one bedroom, 1,000 for two, 1,150 for three, 1,300 for four (§ 500-101).
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. The Town of Chili has no short-term rental law, and a use missing from a residential district's own closed use lists is not automatically available there. The rule is not confirmed, so confirm with the building department before counting on STR income. Separate question from whether you can build the unit.
- Zoning codeecode360.com/12423717
- Building dept(585) 889-6143
Sizing up a specific parcel in Chili?
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 Chili runs $204–268/sq ft, about $370k–480k at 1,800 sq ft , plus roughly $516 for a conforming lot. See what it costs to build a house in Chili.
ADU cost in nearby towns
All Monroe County towns: Rochester (City) · Brighton · Clarkson · 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 Chili: Can you build an ADU here? · Zoning for new construction · Monroe County build cost
ADU cost in Chili: common questions
How much does it cost to build an ADU in Chili, NY?
An 800 sq ft accessory dwelling unit in Town of Chili 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 Chili?
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 Chili?
Town of Chili has 9 districts. All districts prohibit ADUs. Check the specific address with the free ADU checker or confirm with the building department at (585) 889-6143 before you spend money on design.
Can I rent an ADU in Chili short term?
No local short-term-rental law on record - which is not the same as permission for Town of Chili. 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 Chili vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-08-11; verify with the building department at (585) 889-6143 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.