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.
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 (R-20) — 20,000 sf (0.46 acres) with 100 ft of lot width, 200 ft of lot depth and a 50 ft minimum front lot line. Side setback 15 ft, rear 25 ft, height 35 ft, maximum BUILDING coverage 25%. THE FRONT SETBACK IS MEASURED FROM THE HIGHWAY CENTER LINE, NOT FROM THE FRONT PROPERTY LINE, AND THIS IS THE SINGLE MOST MISREADABLE FIGURE IN THE TOWN. § 120-18A states that 'in order to insure that structures shall be set back adequately from highway rights-of-way as they may be established or widened from time to time, structures shall be set back the following distances FROM THE HIGHWAY CENTER LINE': 110 ft on a state or county road and 100 ft on all others. The recorded 100 is the ordinary-road case per county convention, but taken as a property-line setback it is wildly wrong — on a typical 50 to 66 ft right-of-way the effective setback from the front lot line is roughly 67 to 75 ft, and on a widened highway it is less again. ANY BUILDABLE-ENVELOPE CALCULATION FOR RUSH MUST SUBTRACT HALF THE RIGHT-OF-WAY WIDTH FROM THIS NUMBER. The effect is severe on the standard lot: 200 ft of depth less a centerline-referenced front setback and a 25 ft rear leaves a shallow band, and Rush's own 200 ft depth minimum is clearly sized around it. MAXIMUM COVERAGE IS UNAMBIGUOUS HERE BECAUSE § 120-21 PRINTS BOTH BASES SIDE BY SIDE — 'Maximum Building Coverage' 25% and 'Maximum Building Plus Hardscape Coverage' 50% — so 25 is recorded as a true building figure and the 50% hardscape cap is the separate pavement-inclusive limit. Minimum gross floor area is 1,000 sf. Accessory apartments are available by special permit; so is one two-family dwelling per lot, but only if both units stay in single ownership. | 0.4591 ac | 100 / 15 / 25 ft | 35 ft | Special permit |
| Residential 30 (R-30) — 30,000 sf (0.69 acres) with 150 ft of lot width, 200 ft of lot depth and a 50 ft minimum front lot line. Side setback 25 ft (up from R-20's 15 ft), rear 25 ft, height 35 ft, maximum building coverage 25% with a separate 50% building-plus-hardscape cap. Front setback 100 ft on ordinary roads and 110 ft on a state or county road, MEASURED FROM THE HIGHWAY CENTER LINE — see the R-20 note; subtract half the right-of-way width to get the real distance from the front lot line. R-30 HAS NO USE LIST OF ITS OWN AND THAT IS DELIBERATE, NOT AN OMISSION: § 120-8A provides that 'the same uses as are permitted in the R-20 District shall be permitted in the R-30 and RR-5 Residential Districts', so R-30 inherits R-20's permitted and special-permit lists wholesale — including ACCESSORY APARTMENTS and the single-ownership two-family. Anyone reading § 120-8 in isolation will find no accessory apartment and conclude wrongly that R-30 has no ADU route. Minimum gross floor area is 1,200 sf, up from R-20's 1,000. Note that R-30 and R-20 share the same 200 ft depth and the same setbacks except the side yard, so the step from R-20 to R-30 buys width and a bigger side yard rather than a materially different envelope. | 0.6887 ac | 100 / 25 / 25 ft | 35 ft | Special permit |
| Rural Residential 5 (RR-5) — 5 acres with 300 ft of lot width, 300 ft of lot depth and a 50 ft minimum front lot line; the town's largest-lot district. Side setback 50 ft and rear 50 ft, both double R-30's and the largest in Rush; height 35 ft; maximum building coverage 25% with a separate 50% building-plus-hardscape cap. Front setback 100 ft on ordinary roads and 110 ft on a state or county road, MEASURED FROM THE HIGHWAY CENTER LINE — see the R-20 note. LIKE R-30, RR-5 HAS NO USE LIST OF ITS OWN: § 120-8A gives it the same uses as R-20, so ACCESSORY APARTMENTS by special permit and the single-ownership two-family both carry over here despite the rural character and the five-acre minimum. Minimum gross floor area is 1,200 sf. THE COVERAGE CAP IS EFFECTIVELY INERT IN THIS DISTRICT — 25% of five acres is about 54,450 sf of building — so what actually governs an RR-5 site is the 50 ft side and rear yards and the centerline-referenced front setback, not the percentage. Note that RR-5 shares R-20's and R-30's 35 ft height and 25% coverage; Rush holds height and coverage constant across every residential district and varies only lot area, width, depth and the side and rear yards. | 5 ac | 100 / 50 / 50 ft | 35 ft | Special permit |
| Residential Multiple Dwelling (R-MD) — a PER-UNIT DENSITY DISTRICT WITH A PROJECT-SIZE FLOOR, so minLotSize is null by design rather than missing. § 120-17's schedule states 'Minimum Area: 5,500 sq. ft. PER DWELLING UNIT; total area not less than 2 ACRES' — the 2 acres is the minimum size of the development parcel, not the land a dwelling needs, and recording it as a lot minimum would repeat exactly the error that reached a public page for Greece's RM and RS districts. YIELD RUNS ON THE 5,500 SF PER UNIT FIGURE, roughly 7.9 units per acre, subject to the 2-acre entry threshold: a 2-acre R-MD parcel supports about 15 units, not one. Minimum lot width 150 ft, depth 200 ft, front lot line 50 ft. Side setback 25 ft, rear 25 ft, height 35 ft, maximum building coverage 25% with a separate 50% building-plus-hardscape cap. Front setback 100 ft ordinary / 110 ft state or county, MEASURED FROM THE HIGHWAY CENTER LINE — see the R-20 note. Minimum gross floor area is 750 sf PER UNIT, the second-smallest permitted unit in Rush. Note that townhouses are separately provided for: the floor-area schedule carries a distinct line for 'R-20, R-30, R-MD Townhouses' at 1,000 sf per unit, so a townhouse form is contemplated inside R-MD as well as in R-TH. | — | 100 / 25 / 25 ft | 35 ft | No |
| Residential Mobile Home (R-MH) — a per-unit density district with the largest project-size floor in the town, so minLotSize is null by design. The schedule states 'Minimum Area: 10,000 sq. ft. PER DWELLING UNIT; total area not less than 5 ACRES', so yield runs at roughly 4.4 units per acre behind a five-acre entry threshold — the 5 acres is the minimum size of the park, not the land one home needs. THE LOT DIMENSIONS ARE THE SMALLEST IN RUSH AND SIT ODDLY AGAINST THAT LARGE PER-UNIT AREA: minimum lot width just 60 ft, depth 100 ft and a 35 ft front lot line, all well below R-20's 100/200/50 — these are the individual pad dimensions inside the park, while the 10,000 sf per unit figure is the density the park as a whole must satisfy, so the two are measuring different things and neither alone describes a site. Side setback 25 ft, rear 25 ft, height 35 ft, maximum building coverage 25% with a separate 50% building-plus-hardscape cap. Front setback 100 ft ordinary / 110 ft state or county MEASURED FROM THE HIGHWAY CENTER LINE — see the R-20 note. Minimum gross floor area is 600 sf, the smallest permitted dwelling in Rush and less than two thirds of the 1,000 sf R-20 floor. | — | 100 / 25 / 25 ft | 35 ft | No |
| Residential Townhouse (R-TH) — a per-unit density district with the lowest entry threshold in the town: 'Minimum Area: 10,000 sq. ft. PER DWELLING UNIT; total area not less than 1 ACRE', so minLotSize is null by design and yield runs at roughly 4.4 units per acre behind a one-acre floor. R-TH IS THE ONLY DISTRICT IN RUSH WHOSE LOT WIDTH, LOT DEPTH AND FRONT LOT LINE ARE ALL STATED AS ZERO, AND THOSE ZEROS ARE REAL RATHER THAN MISSING DATA — a townhouse district regulates the development parcel and the cluster, not the individual unit lot, so there is no per-unit width or frontage requirement at all. minLotWidthFt is recorded 0 on that basis. THE SETBACKS ARE CLUSTER-RELATIVE AND CARRY THREE SEPARATE FOOTNOTES, which is unique in this town: the side figure is 25 ft BETWEEN A CLUSTER AND A PROPERTY LINE and 50 ft BETWEEN EACH CLUSTER, and the rear 25 ft is measured FROM THE PROPERTY LINE OF THE TOWNHOUSE DEVELOPMENT. The recorded 25 side and 25 rear are the cluster-to-property-line figures; the 50 ft cluster-to-cluster separation is an internal site-planning constraint with no equivalent field here and will often govern the layout before the perimeter setbacks do. Height 35 ft, maximum building coverage 25% with a separate 50% building-plus-hardscape cap. Front setback 100 ft ordinary / 110 ft state or county MEASURED FROM THE HIGHWAY CENTER LINE — see the R-20 note. Minimum gross floor area 1,000 sf per unit. | — | 100 / 25 / 25 ft | 35 ft | No |
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. NO SHORT-TERM RENTAL PROVISION EXISTS IN RUSH. A search of Ch. 120 Zoning (Article II District Regulations alone runs to 105,987 characters) for 'short-term rental' returns nothing, and the whole-code sweep that found dedicated STR chapters in Mendon (Ch. 208) and Gates (Ch. 148) WAS RUN HERE AND CAME BACK EMPTY — all 41 chapters of the Rush Town Code were enumerated from the eCode360 table of contents and none concerns rentals, lodging, licensing, registration or occupancy. That is a materially stronger negative than a zoning-only search, which is why it was done. WHAT RUSH DOES REGULATE IS COMMERCIAL LODGING, AND IT IS RECENT: 'boutique hotels and bed-and-breakfasts' appear as a SPECIAL PERMIT use from the Rush Planning Board, grouped with bars, taverns, restaurants selling alcohol, liquor stores and cannabis retail dispensaries — a commercial-district use list, not a residential one. A bed-and-breakfast is an owner-present commercial lodging use on a special permit and must not be read as authorising a whole-house short-term rental in a residential district. ABSENCE IS NOT PERMISSION: § 120-7C is explicit that 'all uses not specifically permitted by virtue of Subsection A or B of this § 120-7 shall be prohibited in R-20 Residential Districts', and the other residential districts adopt R-20's list — so Rush operates a genuinely closed use list and an unlisted whole-house STR is prohibited rather than merely unaddressed. That closed-list clause is the strongest 'absence is not permission' language found in Monroe so far. strStatus is recorded 'unknown' rather than 'prohibited' only because the closed-list reading has not been confirmed with the Town. New York State's 2025 statewide short-term rental registry (Ch. 99 of the Laws of 2025) obliges every host to register regardless of local law. Confirm with Code Enforcement at (585) 533-1312. Separate question from whether you can build the unit.
- 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 . 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 · Town/Village of 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: Offsite / Aldo cost engine (costEngine.js + constants.js); zoning dataset (municipalData.js).