Plattekill · ADU cost
What it costs to build an ADU in Plattekill, NY
An 800 sq ft accessory dwelling unit in Plattekill runs roughly $200k–265k, or about $252–330/sq ft, and that per-square-foot figure sits deliberately above the $206–270/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 Plattekill maps 8 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 Plattekill
Standard finish, slab on grade, on a flat and clear part of the lot, general-contractor margin included. These are structure costs at Ulster County pricing, before the service and septic work a second dwelling can trigger.
| Size | Type | $ / sq ft | Estimated total |
|---|---|---|---|
| 400 sq ft | Studio | $334–$438 | $135k–175k |
| 600 sq ft | One bedroom | $280–$366 | $170k–220k |
| 800 sq ft | One bedroom, larger | $252–$330 | $200k–265k |
| 1,000 sq ft | Two bedroom | $236–$309 | $235k–310k |
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 | $17–$23 | $17 | — |
| Framing | $26–$32 | $26 | — |
| Envelope - roof, siding, windows | $32–$41 | $32 | — |
| Plumbing | $28–$34 | $17 | 55% |
| Electrical | $19–$24 | $13 | 35% |
| HVAC | $23–$29 | $15 | 45% |
| Insulation | $7–$9 | $7 | — |
| Interior finishes | $33–$44 | $28 | 15% |
| Millwork & cabinetry | $19–$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 Plattekill 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 |
|---|---|---|---|---|
| RS-1 Residential Settlement | 1 ac | 50 / 30 / 30 ft | 35 ft | Occupancy restricted |
| HR-1 Hamlet Residential | 1 ac | 35 / 30 / 30 ft | 35 ft | Occupancy restricted |
| RR-1.5 Rural Residential | 1.5 ac | 50 / 50 / 50 ft | 35 ft | Occupancy restricted |
| AG-1.5 Agricultural | 1.5 ac | 50 / 50 / 50 ft | 35 ft | Occupancy restricted |
| BD-40 Business District | 0.92 ac | 35 / 25 / 25 ft | 35 ft | No |
| BD-60 Light Business District | 1.38 ac | 35 / 25 / 25 ft | 35 ft | No |
| GB-80 General Business District | 1.84 ac | 50 / 50 / 50 ft | 35 ft | No |
| M-3 Mountain District | 3 ac | 50 / 50 / 50 ft | 35 ft | Occupancy restricted |
RS-1 Residential Settlement - The minimum lot drops to 0.75 acre with central sewage and 0.5 acre with central sewage and water. Any central service cuts the front setback to 40 ft and the side and rear to 25 ft, and the minimum width to 125 ft, or 100 ft with both.
- With central sewage and water the building coverage cap rises to 35%.
- Minimum lot depth falls to 175 ft with central water alone and 150 ft with central sewage.
- The minimum lot area is also the land required for each dwelling unit.
HR-1 Hamlet Residential - The minimum lot drops to 0.75 acre with central sewage and 0.25 acre with central sewage and water, where the minimum width falls to 75 ft and the side and rear yards to 20 ft. Any central service cuts the front setback to 25 ft.
- With central sewage and water the building coverage cap rises to 35% and the minimum depth falls to 100 ft.
- With central water alone or central sewage alone the minimum width is 125 ft and the side and rear yards 25 ft, with a depth of 175 ft on water and 150 ft on sewage.
- The minimum lot area is also the land required for each dwelling unit.
RR-1.5 Rural Residential - The minimum lot drops to 1 acre with central sewage and 0.75 acre with central sewage and water. Either way the front, side and rear setbacks fall to 40 ft, the coverage cap rises to 25%, and the minimum width and depth drop to 150 ft, or 125 ft with both.
- The minimum lot area is also the land required for each dwelling unit.
AG-1.5 Agricultural - The lot area shown is also the land required per dwelling unit. These figures are the column for a lot on its own sewage and water, and the schedule prints the same standards in all four of its utility columns.
BD-40 Business District - The minimum lot drops to 30,000 sq ft with central sewage and 20,000 sq ft with central sewage and water, and either of those lifts the coverage cap to 50%. Where the lot abuts a residential district boundary, add 25 ft to the side and rear yards.
- Any central service cuts the front setback to 25 ft and the minimum width to 125 ft, or 100 ft with central sewage and water.
- The side and rear yards fall to 20 ft with central sewage and water; the minimum depth is 175 ft with central water alone and 150 ft with central sewage.
- The minimum lot area is also the land required for each dwelling unit.
BD-60 Light Business District - The minimum lot drops to 40,000 sq ft with central sewage and 30,000 sq ft with central sewage and water, and either of those lifts the coverage cap to 40%. Where the lot abuts a residential district boundary, add 25 ft to the side and rear yards.
- Any central service cuts the front setback to 25 ft; the minimum width and depth fall to 175 ft with central water alone and 150 ft with central sewage.
- With central sewage and water the side and rear yards fall to 20 ft.
- The minimum lot area is also the land required for each dwelling unit.
GB-80 General Business District - With central sewage the minimum lot drops to 40,000 sq ft, with or without central water, and the front, side and rear setbacks fall to 25 ft. Where the lot abuts a residential district boundary, add 25 ft to the side and rear yards.
- Central sewage also lifts the coverage cap to 40% and cuts the minimum width to 125 ft and the minimum depth to 175 ft.
- The minimum lot area is also the land required for each dwelling unit.
M-3 Mountain District - Where the lot abuts a residential district boundary, the side and rear yards go up by 25 ft; the figures shown are for a lot that does not abut one. The lot area shown is also the land required per dwelling unit.
- The schedule prints the same standards in all four of its utility columns, so these figures do not change where central water or central sewage is available.
Size limits on record in Plattekill
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 Plattekill:
- RS-1 Residential SettlementThe lot needs at least 10,000 sq ft per dwelling unit, 20,000 sq ft in total. Ask the Code Enforcement Officer whether § 110-12A instead requires twice the district minimum lot area.
- HR-1 Hamlet ResidentialThe lot needs at least 10,000 sq ft per dwelling unit, 20,000 sq ft in total. Ask the Code Enforcement Officer whether § 110-12A instead requires twice the district minimum lot area.
- RR-1.5 Rural ResidentialThe lot needs at least 10,000 sq ft per dwelling unit, 20,000 sq ft in total. Ask the Code Enforcement Officer whether § 110-12A instead requires twice the district minimum lot area.
- AG-1.5 AgriculturalThe lot needs at least 10,000 sq ft per dwelling unit, 20,000 sq ft in total. Ask the Code Enforcement Officer whether § 110-12A instead requires twice the district minimum lot area.
- M-3 Mountain DistrictThe lot needs at least 10,000 sq ft per dwelling unit, 20,000 sq ft in total. Ask the Code Enforcement Officer whether § 110-12A instead requires twice the district minimum lot area.
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 Central Hudson 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. A short-term rental here needs an annual town permit under Chapter 86, adopted 10-15-2025 by L.L. No. 4-2025, and the chapter reaches every short-term rental, including one operating before it took effect (§ 86-1). Separate question from whether you can build the unit.
- Zoning codeshepstone.net/wp-content/uploads/2016/08/Plattekill.pdf
- Building dept(845) 883-7184
Sizing up a specific parcel in Plattekill?
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 Plattekill runs $206–270/sq ft, about $370k–485k at 1,800 sq ft , plus roughly $13,635 for a conforming lot. See what it costs to build a house in Plattekill.
ADU cost in nearby towns
All Ulster County towns: Kingston (City) · Denning · Esopus · Gardiner · Hardenburgh · Hurley · Lloyd · Marbletown · Marlborough · New Paltz · Olive · Rochester · Rosendale · Saugerties · Shandaken · Shawangunk · Ulster · Wawarsing · Woodstock
More on Plattekill: Can you build an ADU here? · Zoning for new construction · Ulster County build cost
ADU cost in Plattekill: common questions
How much does it cost to build an ADU in Plattekill, NY?
An 800 sq ft accessory dwelling unit in Town of Plattekill runs roughly $200k–265k at a standard finish, general-contractor margin included. A 400 sq ft studio runs about $135k–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 Plattekill?
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 $252–330/sq ft against $206–270/sq ft for a full house, even though it is the same trades doing the same work.
Are ADUs allowed in Plattekill?
Town of Plattekill has 8 districts. 5 districts allow ADUs with occupancy restrictions, 3 do not. Check the specific address with the free ADU checker or confirm with the building department at (845) 883-7184 before you spend money on design.
Can I rent an ADU in Plattekill short term?
Short-term rentals allowed with local rules for Town of Plattekill. 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 Ulster 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 Plattekill vary by district and often carry exceptions this page does not show; zoning last reviewed 2026-08-16; verify with the building department at (845) 883-7184 before relying on any answer. Sources: the Offsite / Aldo cost engine and zoning dataset.