ADU · Columbia County

Can you build an ADU in Hillsdale, NY?

Town of Hillsdale has 3 districts. All districts allow ADUs with occupancy restrictions. Check your address to confirm the district that applies to your parcel:

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What the Hillsdale code says

In a single-family home either the main unit or the accessory apartment must be owner-occupied, and one in an accessory structure must be on an owner-occupied property. It is allowed by right with at least three acres per unit in RU or one acre per unit in HM.

Conditions the code attaches:

In HB an accessory apartment needs a special permit.
On a lot short of that acreage, the Planning Board or ZBA may grant a special permit if the unit meets County Health Department regulations and the rest of the zoning chapter.
Inside a single-family home or a nonresidential building the unit is capped at the lesser of 1,000 sq ft or 30% of the floor space, and in an accessory structure at 1,000 sq ft.
The unit is limited to two bedrooms in RU and in sewered parts of HM, and to one bedroom elsewhere.
In parts of HM served by municipal sewers, the by-right route has no minimum lot size requirement.
The lot may hold no more than one existing dwelling unit at the time of application.

What the Hillsdale 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	3 ac	50 / 50 / 100 ft	35 ft	Occupancy restricted
Hamlet	1 ac	25 / 30 / 20 ft	35 ft	Occupancy restricted
Hamlet Business	1 ac	40 / 50 / 100 ft	35 ft	Occupancy restricted

Rural - Beyond lot area and width, a lot has to contain a square measuring at least 200 ft on a side. The front setback shown applies to a town or county road; it is 70 ft on a state road and 30 ft on a private road.

A flexible lot subdivision under § 245-22 is barely the same district: the side yard falls from 50 ft to 10 ft, the rear from 100 ft to 20 ft, and the front from 50 ft to 40 ft on a town road.
Maximum impermeable surface rises from 10% to 60%, the buildable square drops from 200 ft to 40 ft, and that column publishes no minimum lot size or town-road frontage; it is not available by right.
Minimum road frontage is 200 ft on a town or county road, 300 ft on a state road and 100 ft on a private road.
The coverage cap limits impermeable surface, not building footprint alone.

Hamlet - A lot here must contain a square of at least 100 ft in each dimension, a requirement separate from lot area and width, and needs 100 ft of road frontage on a town or county road, 200 ft on a state road.

Clustering takes the side yard from 30 ft to 10 ft and the rear from 20 ft to 10 ft, and raises maximum impermeable surface from 20% to 80%; the cluster column publishes no minimum lot size.
HM also sets a front-yard maximum: 40 ft on a town or county road and 80 ft on a state road.
The front setback shown applies to a town or county road. On a state road the front setback is 40 ft.
The coverage figure is a cap on impermeable surface, not on buildings alone.
In the Hamlet District the Planning Board may permit more than one building or use on a single lot.
Dimensional and setback requirements are applied in light of the siting guidelines in Appendixes I and II (§ 245-21), and supplementary dimensional regulations are in § 245-27.

Hamlet Business - Beyond the one acre minimum, a lot must also contain a square of at least 400 ft minimum dimension. The coverage figure shown is a cap on total impermeable surface, not on buildings alone.

On a state road the front setback is 50 ft rather than the figure shown.
Minimum road frontage is 100 ft on a town or county road and 400 ft on a state road.
Lot size and density are further governed by § 245-26.
Dimensional and setback requirements are applied in light of the siting guidelines in Appendixes I and II, and the guidelines are consulted where the two conflict (§ 245-21).
See § 245-27 for supplementary dimensional regulations and § 245-66 for existing nonconforming lots.

ADUs vs. short-term rentals in Hillsdale

Short-term rentals allowed with local rules for Town of Hillsdale. Renting a home for stays of under 30 days is regulated here. An owner needs a special permit from the ZBA and a certificate of occupancy from the building inspector before renting short term. 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 minimum1–3 ac — an ADU still has to fit the district's lot and setback envelope.
UtilityNYSEG territory.
Zoning codeecode360.com/HI4009
Building dept(518) 325-5073

ADU FAQ — Hillsdale, NY

Are ADUs allowed in Hillsdale, NY?

Town of Hillsdale has 3 districts. All districts allow ADUs with occupancy restrictions. Check your address with the free ADU checker, or confirm with the building department at (518) 325-5073.

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

No district in Town of Hillsdale requires a special-use permit for an ADU - 3 districts allow ADUs with occupancy restrictions. Site-plan review or a building permit may still apply.

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

Short-term rentals allowed with local rules for Town of Hillsdale. 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.

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What an ADU costs to build in Hillsdale

Permission is one question and budget is another. An 800 sq ft accessory unit here runs roughly $195k–260k 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 Hillsdale, priced by size.

How we know this

Sections analyzed: § 245-15 (Use table) · § 245-25B · § 245-91
Districts confirmed: 3 of 3 — every mapped district.
Last reviewed: 2026-06-02
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 Hillsdale: Full zoning for new construction · ADU build cost · House build cost · ADU rules across Columbia County · All Columbia County towns

ADU information for Town of Hillsdale is compiled from the municipal code (last reviewed 2026-06-02) 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 (518) 325-5073 before relying on any answer. Source: the Offsite / Aldo zoning dataset.