ADU · Westchester County
Can you build an ADU in New Castle, NY?
Town of New Castle has 17 districts. 9 districts prohibit ADUs, 8 allow them with occupancy restrictions. Check your address to confirm the district that applies to your parcel:
What the New Castle 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 |
|---|---|---|---|---|
| Multifamily Planned Development | 5 ac | — | 35 ft | No |
| One-Family Residence | 2 ac | — | 35 ft | Occupancy restricted |
| One-Family Residence | 2 ac | — | 35 ft | Occupancy restricted |
| Multifamily Residence - Chappaqua | 1 ac | — | 35 ft | No |
| Multifamily Residence - Millwoood | 1 ac | — | 35 ft | No |
| One-Family Residence | 0.5 ac | — | 35 ft | Occupancy restricted |
| One-Family Residence | 0.5 ac | — | 35 ft | Occupancy restricted |
| One-Family Residence | 1 ac | — | 35 ft | Occupancy restricted |
| One-Family Residence | 1 ac | — | 35 ft | Occupancy restricted |
| One-Family Residence | 1 ac | — | 35 ft | Occupancy restricted |
| One-Family Residence | 0.2583 ac | — | 35 ft | Occupancy restricted |
| Research and Office Business | 20 ac | — | 40 ft | No |
| Designed Business | 0.1148 ac | — | 30 ft | No |
| Retail Business | 0.1148 ac | — | 35 ft | No |
| Retail Business and Parking | 0.1148 ac | — | 30 ft | No |
| General Industrial | 15 ac | — | 30 ft | No |
| Planned Industrial | 0.1722 ac | — | 30 ft | No |
ADUs vs. short-term rentals in New Castle
No local short-term-rental law on record - which is not the same as permission for Town of New Castle. No local STR ordinance found as of Jun 2026; standard town zoning and building codes apply. Westchester County hotel occupancy tax (3%) applies to short-term stays. 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 minimum0.2583–2 ac — an ADU still has to fit the district's lot and setback envelope.
- UtilityCon Edison territory.
- Building dept(914) 238-4723
- Last reviewed2026-06-08
ADU FAQ — New Castle, NY
Are ADUs allowed in New Castle, NY?
Town of New Castle has 17 districts. 9 districts prohibit ADUs, 8 allow them with occupancy restrictions. Check your address with the free ADU checker, or confirm with the building department at (914) 238-4723.
Do I need a special permit for an ADU in New Castle?
No district in Town of New Castle requires a special-use permit for an ADU - 9 districts prohibit ADUs, 8 allow them with occupancy restrictions. Site-plan review or a building permit may still apply.
Can I use an ADU as a short-term rental in New Castle?
No local short-term-rental law on record - which is not the same as permission for Town of New Castle. 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.
What an ADU costs to build in New Castle
Permission is one question and budget is another. An 800 sq ft accessory unit here runs roughly $235k–310k 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 New Castle, priced by size.
More on New Castle: Full zoning for new construction · ADU build cost · House build cost · All Westchester County towns
ADU information for Town of New Castle is compiled from the municipal code (last reviewed 2026-06-08) 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 (914) 238-4723 before relying on any answer. Source: Offsite / Aldo zoning dataset, municipalData.js.