Collins · ADU cost
What it costs to build an ADU in Collins, NY
An 800 sq ft accessory dwelling unit in Collins 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 Collins maps 4 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 Collins
Standard finish, slab on grade, on a flat and clear part of the lot, general-contractor margin included. These are structure costs at Erie 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 Collins 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 District | 0.46 ac | 40 / 10 / 50 ft | 30 ft | Occupancy restricted |
| Residential-Agricultural District | 0.92 ac | 40 / 10 / 50 ft | 30 ft | Occupancy restricted |
| Commercial District | 0.92 ac | 25 / 10 / 25 ft | 30 ft | Occupancy restricted |
| Manufacturing District | — | 25 / 10 / 25 ft | — | No |
Residential District - Neither side yard figure is fixed: the two side yards together must total 25% of the lot width, with 10 ft the least either one may be, so on the minimum 100 ft lot the pair comes to 25 ft and on a 200 ft lot to 50 ft.
- The rear yard must equal 25% of the lot depth but need not exceed 50 ft, so the 50 ft figure is a ceiling that a lot under 200 ft deep never reaches
- Lot width is measured at the building line
- Collins publishes no lot-coverage or impervious standard in any district
Residential-Agricultural District - The per-unit floor governs any multi-unit proposal: the lot must be 40,000 sq ft and not less than 20,000 sq ft per dwelling unit, so a two-unit building fills the minimum exactly and a third unit pushes past it.
- The two side yards together must total 25% of the lot width, with 10 ft the least either one may be, so the pair comes to 25 ft on the minimum 100 ft lot and 50 ft on a 200 ft lot
- The rear yard must equal 25% of the lot depth but need not exceed 50 ft, so the 50 ft figure is a ceiling that a lot under 200 ft deep never reaches
- Farm structures have no height limit at all, against 30 ft for anything residential
Commercial District - The 10 ft side and 25 ft rear yards apply only where the lot adjoins the R or R-A district. Between two commercial lots the code sets no side or rear yard at all.
- The lot minimum is the same 40,000 sq ft, and 20,000 sq ft per dwelling unit, that the Residential-Agricultural district takes, because every use permitted there is permitted here
Manufacturing District - Height here is a ratio rather than a figure: a building may be no taller than its setback from the street line, so one set 25 ft back may be 25 ft tall and one set 60 ft back may be 60 ft.
- The 10 ft side and 25 ft rear yards apply only where the lot adjoins the R or R-A district; between two industrial lots the code sets none
- No lot area and no lot width are stated for this district
- Every use beyond those already permitted in the Residential-Agricultural and Commercial districts needs a special use permit from the Town Board
- That permit is granted only where the use sends no dust, smoke, fumes, noise, vibration or odour past the boundary and casts no glare observable from a residential district
Size limits on record in Collins
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 Collins:
- Residential DistrictAn R lot must be at least 20,000 sq ft
- Residential-Agricultural DistrictAn R lot must be at least 20,000 sq ft
- Commercial DistrictAn R lot must be at least 20,000 sq ft
- Manufacturing DistrictAn R lot must be at least 20,000 sq ft
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 National Grid 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. Collins has no local short-term rental law. That is not the same as permission, so confirm with the town before counting on renting a home short term. Separate question from whether you can build the unit.
- Zoning codeecode360.com/27330501
- Building dept(716) 532-4887
Sizing up a specific parcel in Collins?
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 Collins runs $204–268/sq ft, about $370k–480k at 1,800 sq ft , plus roughly $2,460 for a conforming lot. See what it costs to build a house in Collins.
ADU cost in nearby towns
All Erie County towns: Buffalo (City) · Lackawanna (City) · Tonawanda (City) · Alden · Amherst · Aurora · Boston · Brant · Cheektowaga · Clarence · Colden · Concord · Eden · Elma · Evans · Grand Island · Hamburg · Holland · Lancaster · Marilla · Newstead · North Collins · Orchard Park · Sardinia · Tonawanda · Wales · West Seneca · Akron (Village) · Alden (Village) · Angola (Village) · Blasdell (Village) · Depew (Village) · East Aurora (Village) · Farnham (Village) · Gowanda (Village) · Hamburg (Village) · Kenmore (Village) · Lancaster (Village) · North Collins (Village) · Orchard Park (Village) · Sloan (Village) · Springville (Village) · Williamsville (Village)
More on Collins: Can you build an ADU here? · Zoning for new construction · Erie County build cost
ADU cost in Collins: common questions
How much does it cost to build an ADU in Collins, NY?
An 800 sq ft accessory dwelling unit in Town of Collins 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 Collins?
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 Collins?
Town of Collins has 4 districts. 3 districts allow ADUs with occupancy restrictions, 1 does not. Check the specific address with the free ADU checker or confirm with the building department at (716) 532-4887 before you spend money on design.
Can I rent an ADU in Collins short term?
No local short-term-rental law on record - which is not the same as permission for Town of Collins. 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 Erie 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 Collins vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-09-10; verify with the building department at (716) 532-4887 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.