ADU · Sullivan County

Can you build an ADU in Thompson, NY?

Town of Thompson has 8 districts. 5 districts prohibit ADUs, 3 allow them. Check your address to confirm the district that applies to your parcel:

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What the Thompson code says

In RR-1, RR-2 and SR, a second detached single-family house is permitted with a building permit on a lot large enough to be subdivided under the district's standard minimums. Both houses must stay in common ownership.

Conditions the code attaches:

If either house is to be sold, subdivision approval from the Planning Board must come first.
Each house must meet the district's yard and size requirements on its own, so a lot of only the district minimum does not qualify.
Land needed per house: SR 20,000 sq ft with central water or sewer or 40,000 sq ft without, RR-1 40,000 sq ft, RR-2 2 acres.
The zoning does not restrict who may live in the second house or bar renting it.
Whether renting the second house needs a rental registration or license is not confirmed; ask the building department at (845) 794-2500.
HC-1 and HC-2 cap single-family dwellings at one per lot, new one- and two-family houses are prohibited in EBG, E has no dwellings, and CI's only dwellings are for agricultural or security staff.

What the Thompson 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
Suburban Residential District	0.92 ac	50 / 20 / 50 ft	30 ft	As of right
Rural Residential-1 District	0.92 ac	50 / 20 / 50 ft	30 ft	As of right
Rural Residential-2 District	2 ac	50 / 20 / 50 ft	30 ft	As of right
Highway Commercial-1 District	0.46 ac	40 / 25 / 50 ft	35 ft	No
Highway Commercial-2 District	0.46 ac	40 / 25 / 50 ft	35 ft	No
Commercial Industrial District	3 ac	40 / 25 / 50 ft	35 ft	No
Extractive Industry District	50 ac	200 / 50 / 50 ft	35 ft	No
East Broadway Gateway District	0.92 ac	40 / 25 / 50 ft	35 ft	No

Suburban Residential District - A home here needs 40,000 square feet, 0.9183 acre, on a lot 150 feet wide and 150 feet deep, set back 50 feet at the front, 50 feet at the rear and 20 feet on one side, with 50 feet for both sides together. Buildings cover up to 10% of the lot and reach 30 feet.

With central water or sewer the dwelling takes 20,000 square feet, 0.4591 acre, on 100 feet of width and 125 feet of depth, with 40 foot front and rear yards, 15 feet one side and 40 feet both sides.
That smaller lot carries 20% coverage, 2.0 units per acre and 1,000 square feet of habitable floor area per unit, at the same 30 feet of height.
A cluster development for one-family detached dwellings under § 250-26 needs site plan review and takes 10 acres plus 7,500 square feet per unit, on lots 65 feet wide and 90 feet deep.
Those cluster lots take 30 foot front and rear yards, 10 feet one side, 25 feet both sides, 2.0 units per acre and 25% coverage.
Multiple dwellings under § 250-28 need site plan review on 10 acres, 150 feet of width and depth, 40 feet front, 50 feet rear, 30 feet one side, 50 feet both sides and 35 feet of height.
Row houses and attached dwellings under § 250-28 need a special use permit on 10 acres, lots 22 feet wide and 100 feet deep, 30 feet front, 35 feet rear, 4 feet one side and 25 feet both sides.

Rural Residential-1 District - A home here needs 40,000 square feet, 0.9183 acre, on a lot 150 feet wide and 150 feet deep, set back 50 feet at the front, 50 feet at the rear and 20 feet on one side, with 50 feet for both sides together. Buildings cover up to 10% of the lot and reach 30 feet.

A dwelling must hold at least 1,000 square feet of habitable floor area per unit and be at least 20 feet wide, at 1.0 dwelling unit per acre.
A two-family dwelling needs site plan review and takes the same lot area, width, depth, yards, height and coverage as a one-family dwelling.
A mobile home park under § 250-25 needs site plan review on 10 acres, lots 400 feet wide and 400 feet deep, 80 feet front, 50 feet rear, 50 feet one side and 100 feet both sides.
That park takes 4.0 units per acre, 20% coverage and 20 feet of height, with 720 square feet per unit at 12 feet of width.
A planned unit development under § 250-27 needs site plan review on 30 acres, lots 500 feet wide and 500 feet deep, 100 feet front, 50 feet rear, 50 feet one side and 100 feet both sides.
That development takes 1,000 square feet of habitable floor area, 2.0 units per acre, 15% coverage and 30 feet of height.

Rural Residential-2 District - A home here needs 2 acres on a lot 150 feet wide and 300 feet deep, set back 50 feet at the front, 50 feet at the rear and 20 feet on one side, with 50 feet for both sides together. Buildings cover up to 10% of the lot and reach 30 feet.

A dwelling must hold at least 1,000 square feet of habitable dwelling area and be at least 20 feet wide, at 1.0 dwelling unit per acre.
A two-family dwelling needs site plan review and takes the same lot area, width, depth, yards, height and coverage as a one-family dwelling.
A cluster development under § 250-26 needs site plan review on 10 acres plus 7,500 square feet per dwelling unit, with lots 65 feet wide and 90 feet deep.
Those cluster lots take 30 foot front and rear yards, 10 feet one side, 25 feet both sides, 0.5 dwelling unit per acre, 30% coverage and 35 feet of height.
Summer camps and campgrounds under §§ 250-31 and 250-34 take 10 acres, lots 400 feet wide and deep, 100 feet front, 50 feet rear, 50 feet one side, 100 feet both sides and 10% coverage.
An airport takes 100 acres, lots 1,000 feet wide and 4,000 feet deep, 50 foot front, rear and one side yards, 100 feet both sides, 15% coverage and 45 feet of height.

Highway Commercial-1 District - A shop, restaurant or service building here needs 20,000 square feet, 0.4591 acre, on a lot 100 feet wide and 125 feet deep, set back 40 feet at the front, 50 feet at the rear and 25 feet on one side, with 50 feet for both sides, at 30% coverage and 35 feet.

A one-family dwelling with central water and sewer takes 20,000 square feet, 0.4591 acre, 100 feet of width, 125 feet of depth, 40 foot front and rear yards, 15 feet one side and 40 feet both sides.
Without central water and sewer that dwelling takes 40,000 square feet, 0.9183 acre, 150 feet of width and depth, 50 foot front and rear yards, 20 feet one side, 50 feet both sides and 10% coverage.
A dwelling holds at least 1,000 square feet of habitable floor area and reaches 30 feet, at 2.0 dwelling units per acre on the smaller lot and 1.0 on the larger, with 20% coverage on the smaller.
Multiple dwellings under § 250-28 need a special use permit on 10 acres, 150 feet of width and depth, 40 feet front, 50 feet rear, 30 feet one side, 50 feet both sides and 20% coverage.
Row houses and attached dwellings under § 250-28 need a special use permit on 10 acres, lots 22 feet wide and 100 feet deep, 30 feet front, 35 feet rear, 4 feet one side and 25 feet both sides.
A mobile home park under § 250-25 needs a special use permit on 10 acres, lots 400 feet wide and deep, 80 feet front, 50 feet rear, 50 feet one side, 100 feet both sides and 7 units per acre.

Highway Commercial-2 District - A shop, restaurant or service building here needs 20,000 square feet, 0.4591 acre, on a lot 100 feet wide and 125 feet deep, set back 40 feet at the front, 50 feet at the rear and 25 feet on one side, with 50 feet for both sides, at 30% coverage and 35 feet.

A one-family dwelling with central water and sewer takes 20,000 square feet, 0.4591 acre, 100 feet of width, 125 feet of depth, 40 foot front and rear yards, 15 feet one side and 40 feet both sides.
Without central water and sewer that dwelling takes 40,000 square feet, 0.9183 acre, 150 feet of width and depth, 50 foot front and rear yards, 20 feet one side, 50 feet both sides and 10% coverage.
A dwelling holds at least 1,000 square feet of habitable floor area and reaches 30 feet, at 2.0 dwelling units per acre on the smaller lot and 1.0 on the larger, with 20% coverage on the smaller.
Multiple dwellings under § 250-28 need a special use permit on 10 acres, 150 feet of width and depth, 40 feet front, 50 feet rear, 30 feet one side, 50 feet both sides and 25% coverage.
Row houses and attached dwellings under § 250-28 need a special use permit on 10 acres, lots 22 feet wide and 100 feet deep, 30 feet front, 35 feet rear, 4 feet one side and 25 feet both sides.
A mobile home park under § 250-25 needs a special use permit on 10 acres, lots 400 feet wide and deep, 80 feet front, 50 feet rear, 50 feet one side, 100 feet both sides and 7 units per acre.

Commercial Industrial District - A manufacturing or processing building here needs 3 acres on a lot 250 feet wide and 300 feet deep, set back 40 feet at the front, 50 feet at the rear and 25 feet on one side, with 50 feet for both sides, at 30% coverage and 35 feet.

No use is permitted outright in the district; every use on the schedule needs site plan review and a special use permit.
Retail stores, eating places, funeral homes and motor vehicle service stations take 40,000 square feet on 150 feet of width and depth, 50 feet front and rear, 35 feet one side and 70 feet both sides.
A bed-and-breakfast or inn takes 20,000 square feet with central sewer and 40,000 without, on 100 or 150 feet of width and 125 or 150 feet of depth, at 30% coverage and 35 feet.
A hotel or motel with central sewer takes 1 acre plus 2,000 square feet per unit over 50 units, and without central sewer 10 acres plus 10,000 square feet per unit over 12 units.
Hotels and motels sit on 600 feet of width and 300 feet of depth, 100 feet front, 50 feet rear, 50 feet one side and 100 feet both sides, with 250 square feet per unit and 30% coverage.
Summer camps, bungalow colonies and campgrounds under §§ 250-31 and 250-34 take 10 acres, 400 feet of width and depth, 150 feet front and rear, 100 feet one side and 200 feet both sides.

Extractive Industry District - Quarrying, processing and the stockpiling and distribution of quarry products here need 50 acres on a lot 800 feet wide and 1,000 feet deep, set back 200 feet at the front, 50 feet at the rear and 50 feet on one side, with 100 feet for both sides, and reach 35 feet.

No use is permitted outright in the district; every use on the schedule needs site plan review by the Planning Board.
Every row of the schedule reads N/A for habitable dwelling area, density per acre and percentage of lot coverage.
Storage and maintenance facilities for trucks and equipment, warehouses for supplies, petroleum storage and manufacturing facilities using aggregates are accessory uses here.

East Broadway Gateway District - A retail store, office, eating place or motor vehicle repair shop here needs 40,000 square feet, 0.9183 acre, on a lot 200 feet wide and 200 feet deep, set back 40 feet at the front, 50 feet at the rear and 25 feet on one side, at 30% coverage and 35 feet.

Those business uses need site plan review and a special use permit, and keep 50 feet for both side yards together.
A one-family dwelling with central water and sewer takes 20,000 square feet, 0.4591 acre, 100 feet of width, 125 feet of depth, 40 foot front and rear yards, 15 feet one side and 40 feet both sides.
Without central water and sewer that dwelling takes 40,000 square feet, 150 feet of width and depth, 50 foot front and rear yards, 20 feet one side, 50 feet both sides and 10% coverage.
A dwelling holds at least 1,000 square feet of habitable floor area, is at least 20 feet wide and reaches 30 feet, at 2.0 dwelling units per acre with central service and 1.0 without.
A mixed-use development needs a special use permit on 10 acres, 150 feet of width, 300 feet of depth, 50 foot front and rear yards, 35 feet one side, 70 feet both sides and 4 units per acre.
A hotel and motel takes 7,500 square feet plus 1,500 square feet per rental unit, on 200 feet of width and depth, 40 feet front, 50 feet rear, 25 feet one side and 50 feet both sides.

ADUs vs. short-term rentals in Thompson

No local short-term-rental law on record - which is not the same as permission for Town of Thompson. As of June 2026 the Town of Thompson has no local law specific to short-term rentals. That is not the same as permission, so confirm with the building department before counting on 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 minimum0.92–2 ac — an ADU still has to fit the district's lot and setback envelope.
UtilityNYSEG territory.
Zoning codeecode360.com/TH0750
Building dept(845) 794-2500

ADU FAQ — Thompson, NY

Are ADUs allowed in Thompson, NY?

Town of Thompson has 8 districts. 5 districts prohibit ADUs, 3 allow them. Check your address with the free ADU checker, or confirm with the building department at (845) 794-2500.

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

No district in Town of Thompson requires a special-use permit for an ADU - 5 districts prohibit ADUs, 3 allow them. Site-plan review or a building permit may still apply.

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

No local short-term-rental law on record - which is not the same as permission for Town of Thompson. 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 Thompson

Permission is one question and budget is another. An 800 sq ft accessory unit here runs roughly $190k–250k 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 Thompson, priced by size.

How we know this

Sections analyzed: Ch. 250 Schedules of District Regulations, Attachments 1-7 and 9, Note 1 to the SR/RR-1/RR-2 schedules; § 250-46A(3); EBG provisions added by L.L. No. 2-2020
Districts confirmed: 8 of 8 — every mapped district.
Last reviewed: 2026-10-07
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 Thompson: Full zoning for new construction · ADU build cost · House build cost · ADU rules across Sullivan County · All Sullivan County towns

ADU information for Town of Thompson is compiled from the municipal code (last reviewed 2026-10-07) 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) 794-2500 before relying on any answer. Source: the Offsite / Aldo zoning dataset.