ADU · Dutchess County

Can you build an ADU in Washington, NY?

Town of Washington has 9 districts. 7 districts allow ADUs with a special-use permit, 2 do not. Check your address to confirm the district that applies to your parcel:

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What the Washington code says

A barn or outbuilding that existed on January 1, 1989 can become a unit by Planning Board special permit in RR-10, RS-10, RL-5, RS-5, RM-2, RH-1 and HM, and may be rented. New accessory housing in the R districts is also by special permit, only where the owner lives on the lot.

Conditions the code attaches:

A converted unit must be at least 800 sq ft, with one converted building per lot, though the Planning Board may allow up to three.
The converted unit must be on the same lot as a house, and may share its water and septic where the Health Department allows.
New accessory housing may be attached or detached, one per lot.
New accessory housing needs twice the single-family acreage, 20 acres in the ten-acre districts and 10 acres in the five-, two- and one-acre districts, subject to ZBA area relief.

What the Washington code indicates by district

The table below shows how each district treats ADUs, alongside the lot and setback standards that govern a second unit. District boundaries and conditions vary, so treat this as a starting point and confirm the district that applies to your parcel.

District	Min lot	Setbacks F / S / R	Max height	ADU
Rural Residential 10-Acre	10 ac	100 / 100 / 75 ft	35 ft	Special permit
Rural Residential Special 10-Acre	10 ac	100 / 100 / 75 ft	35 ft	Special permit
Low Density Residential 5-Acre	5 ac	100 / 75 / 75 ft	35 ft	Special permit
Low Density Residential Special	5 ac	100 / 75 / 75 ft	35 ft	Special permit
Medium Density Residential 2-Acre	2 ac	75 / 50 / 50 ft	35 ft	Special permit
High Density Residential 1-Acre	1 ac	50 / 30 / 25 ft	35 ft	Special permit
Hamlet Mixed-Use	1 ac	50 / 30 / 25 ft	35 ft	Special permit
Land Conservation	10 ac	100 / 100 / 75 ft	15 ft	No
Hamlet (floating district)	0.25 ac	20 / 15 / 25 ft	35 ft	No

Rural Residential 10-Acre, Rural Residential Special 10-Acre - Height is capped at 2 1/2 stories as well as 35 ft, and the lot needs at least 400 ft of road frontage, a separate requirement from lot width.

Rear lot frontage is governed by § 165-68.

Low Density Residential 5-Acre, Low Density Residential Special - Height is capped at 2 1/2 stories as well as 35 ft, and the lot needs at least 300 ft of road frontage, a separate requirement from lot width.

Rear lot frontage is governed by § 165-68.

Medium Density Residential 2-Acre, High Density Residential 1-Acre - Height is capped at 2 1/2 stories as well as 35 ft, and the lot needs at least 200 ft of road frontage, a separate requirement from lot width.

Rear lot frontage is governed by § 165-68.

Hamlet Mixed-Use - The figures shown are for residential uses. A non-residential use needs half an acre, 100 ft of lot width, an 80 ft front yard, a 15 ft side yard and a 50 ft rear yard, with coverage up to 60%.

A residential building is also capped at 2 1/2 stories; the non-residential cap is 35 ft.
Minimum road frontage is 100 ft.
Rear lot frontage is governed by § 165-68.

Land Conservation - Height is capped at 1 story as well as 15 ft, the lowest in the Town, and the lot needs at least 400 ft of road frontage, a separate requirement from lot width.

Rear lot frontage is governed by § 165-68.

Hamlet (floating district) - H is a floating district under § 165-13 that applies only once the Town Board maps it, replacing the district previously in place. The quarter-acre minimum is a floor, and the lot must have any greater area the Dutchess County Department of Health requires.

On an unsewered lot, the Health Department's requirement is usually a great deal more.
The front and side yards also have maximums of 50 ft each, build-to limits on top of the minimums shown.
Height is capped at 2 1/2 stories as well as 35 ft.
Minimum road frontage is 50 ft.
Rear lot frontage is governed by § 165-68.

ADUs vs. short-term rentals in Washington

Short-term rentals allowed with local rules for Town of Washington. A short-term rental needs a Town permit under Chapter 115, adopted 1-31-2024, and § 115-3 caps how many permits may be issued. Advertising the property is itself treated as evidence of short-term rental use (§ 115-2). These are separate questions from whether you can build an ADU — a unit you're allowed to add isn't automatically one you're allowed to rent nightly, so check both.

Good to know

Residential lot minimum0.25–10 ac — an ADU still has to fit the district's lot and setback envelope.
UtilityCentral Hudson territory.
Zoning codeecode360.com/37495610
Building dept(845) 677-3419

ADU FAQ — Washington, NY

Are ADUs allowed in Washington, NY?

Town of Washington has 9 districts. 7 districts allow ADUs with a special-use permit, 2 do not. Check your address with the free ADU checker, or confirm with the building department at (845) 677-3419.

Do I need a special permit for an ADU in Washington?

It depends on the district: 7 of 9 require a special-use permit, the rest do not. Check the district that applies to your parcel before you design.

Can I use an ADU as a short-term rental in Washington?

Short-term rentals allowed with local rules for Town of Washington. ADU occupancy and short-term-rental rules are separate: an ADU you can build isn't automatically one you can rent nightly. Confirm both before you count on STR income.

Run the free ADU check for your parcel →

What an ADU costs to build in Washington

Permission is one question and budget is another. An 800 sq ft accessory unit here runs roughly $210k–275k at a standard finish, and the per-square-foot rate comes in above a full house because the kitchen, bath, panel and heating plant cost the same either way. See the full cost to build an ADU in Washington, priced by size.

How we know this

Sections analyzed: Ch. 165 Appendix A Schedule of District Use Regulations (Aug 2024); § 165-21A; § 165-40 Conversion of barns and accessory buildings; § 165-41 Accessory residential housing; § 165-70D; § 165-13 and § 165-29 Hamlet District
Districts confirmed: 9 of 9 — every mapped district.
Last reviewed: 2026-08-16
Not covered here: Overlay districts, the zoning map, and any conditions attached to an individual parcel. Size limits and owner-occupancy terms sit in the code section above, not in this summary.

More on Washington: Full zoning for new construction · ADU build cost · House build cost · ADU rules across Dutchess County · All Dutchess County towns

ADU information for Town of Washington is compiled from the municipal code (last reviewed 2026-08-16) and provided for decision-support only — not legal or architectural advice. ADU eligibility, size, owner-occupancy and permit conditions vary by district and often carry exceptions; verify with the building department at (845) 677-3419 before relying on any answer. Source: the Offsite / Aldo zoning dataset.