Southampton ADU Zoning Guide

Last reviewed 2026-04-26

Max size1,000 sq ft
Owner occupancyRequired

Southampton has established clear ADU guidelines that, while having specific requirements, provide a pathway for homeowners to build on their existing property. Whether you're considering a primary residence for a family member, a rental income source, or an independent square footage for your growing family, understanding the local zoning rules is essential to moving forward with confidence. We've reviewed Southampton's zoning regulations in detail and outlined the key requirements below. Rules can change, so confirm details with the Southampton Planning Department or book a free consultation with our team before starting your project.

Status

Adoption status: Active — accessory apartments are regulated under Chapter 330 Sections 330-11.1 and 330-11.2 of the Southampton Town Code; rental permits are required under Chapter 270
Governing ordinance: Southampton Town Code Chapter 330 Sections 330-11.1 and 330-11.2; Chapter 270 (rental permit); application renewed every two years
Fee waiver: Permit fee waived for income-eligible accessory apartments approved after January 1, 2019

Eligibility

Where ADUs are allowed

Zoning districts permitted: Accessory apartments are permitted in hamlets defined as Census Designated Places (CDPs) where the density is under 500 persons per square mile
Lot type / use restrictions: Single-family lots only; lots must conform to current district area and dimensional regulations
Minimum lot area required: Standard: more than 30,000 sq ft
Limit per property: One ADU per lot

Types allowed

Attached ADU (interior conversion): Yes
Attached ADU (addition): Yes
Detached ADU (new construction): Yes
Detached ADU (accessory structure conversion): Yes — converted garage or other accessory building

Size and placement

Size limits

Minimum sq ft: 400 sq ft
Maximum sq ft: The lesser of 35% of the total floor area of the principal dwelling or 1,000 sq ft
Example: A main home of 2,500 sq ft can have an ADU up to 875 sq ft; a main home of 2,857 sq ft or larger caps the ADU at 1,000 sq ft

Setbacks

General rule: The lot must meet all town code required setbacks; dimensional nonconformities for nonconforming lots shall be not less than 70% of the required setback or lot width
Specific numeric setbacks by zone: Not reproduced in the retrieved application documents; the lot must comply with the applicable district setback requirements per Chapter 330; consult the Southampton Code Enforcement office for zone-specific numbers

Rules for use

Parking

Studio or one-bedroom ADU: At least 1 additional off-street parking space required
Two-bedroom ADU: At least 2 additional off-street parking spaces required
Location restriction: Parking spaces may not be located in the required minimum front yard; must be adequately screened with landscape plantings including evergreen shrubs not less than 3 ft in height at installation

Owner occupancy

Required: Yes — the homeowner and tenant must both reside in the house year-round as their principal place of residence
Year-round: Summer or short-term rentals are NOT permitted; both owner and tenant must occupy the property year-round

Rental use

Short-term rental: Not permitted — both owner and tenant must reside year-round; summer rentals not permitted
Long-term rental: Permitted; lease can be maximum two years; upon renewal, Housing provides new rent allowed
Affordable track rent: Monthly rent for affordable ADUs is set at HUD Fair Market Rents for the New York Metropolitan area; rent is fixed for the lease term and may change on renewal
Rental permit renewal: Accessory Apartment Rental Permit must be renewed every two years

How to apply in Southampton

Required permit: Rental Permit from Code Enforcement Investigations and Enforcement Unit; application is CP-18026
Required documents: Building Department Certificate of Compliance or Certificate of Occupancy; current survey; 2 proofs of residency (driver's license AND current utility bill OR voter registration); floor plans showing bedrooms, sq ft, and smoke/CO detector locations; Housing Department Affordable Accessory Apartment Tenant Qualification Certification Form and Lease Waiver; Land Management Department Final Development Right Extinguishment Form
Permit fees: Renewal fee $250; fee waived for income-eligible affordable ADUs approved after January 1, 2019
Tenant qualification: The Housing Department qualifies tenants as low/moderate or middle income; homeowner may find their own tenant and have them income-qualified by Housing
Contact: Code Enforcement Investigations and Enforcement Unit, 27 Ponquogue Avenue, Hampton Bays, NY 11946; (631) 702-1700

Recent and pending changes

March 2026 permit form update (CP-18026 rev 03/2026)
The Accessory Apartment Application was revised in March 2026, indicating the regulatory framework remains active and current
August 2024 Affordable Accessory Apartment Requirements update (CP-32265 rev 8/24)
The Affordable Accessory Apartment Requirements were updated in August 2024

Important details

Community Housing Fund (CHF) zero-interest ADU loan: Up to $125,000, repaid over 20 years or at resale/refinancing. The ADU must house a Southampton workforce tenant (full-time worker in Southampton) whose household income is at or below 130% of Nassau/Suffolk AMI. The ADU cannot remain vacant for more than 6 months without Town approval
Development right extinguishment: Applications require a Land Management Department Final Development Right Extinguishment Form — this means an ADU will extinguish a development right on the parcel
Hamlet density restriction: ADUs are only permitted in hamlets that are Census Designated Places with density under 500 persons per square mile — this is a geographic restriction that eliminates many Southampton areas

Frequently asked questions

What's the minimum lot size for adding an ADU in Southampton?

Most of Southampton requires a minimum of 30,000 square feet. However, if your property is in a census-designated place with fewer than 500 people per square mile, the minimum drops to 20,000 square feet. Check with the Town Planning Department to confirm your location's requirements.

Can I rent out my ADU as a short-term rental or Airbnb in Southampton?

No. Southampton's zoning code prohibits having both an accessory apartment and a rental permit on the same property. Additionally, short-term rentals must be 14 days or longer. This means your ADU must be rented long-term to a permanent tenant, not used for vacation or Airbnb-style rentals.

Do I need approval from Southampton's Board of Architectural Review for my ADU?

Yes, if your ADU requires structural alterations to the exterior of the existing dwelling. Before the Building Inspector will issue a permit, the full Board of Architectural Review must approve your plans. This is especially important in the Hamptons area due to aesthetic and historic preservation concerns.

Sources (5)

Last reviewed 2026-04-26. Local rules can change — verify the latest details with the Southampton planning department, or book a free consultation with our team before starting your project. This page is informational and is not legal advice.

Southampton ADU regulations.