Southampton, NY Accessory Structures: ADU Owner Occupancy (2026)

The Department of Land Management will not issue or renew a building permit or rental permit for an accessory apartment unless the lot owner actually lives in the Town of Southampton outside the villages. Section 330-11.2A states that the owner or owners of the lot on which the accessory apartment sits must reside within the principal dwelling or the accessory apartment, and that dwelling or apartment must be the owner's domicile or principal place of abode. No co-owner may hold a larger ownership share than the resident owner-occupant, which blocks investors from using a minority partner as a strawman resident.

The only carve-out is for lots held by the Southampton Housing Authority or a nonprofit agency it transfers title to, and even that exemption requires Town Board approval on a lot-by-lot basis. Section 330-11.2M, added by Local Law 3-2019, goes further: the owner-occupant alone may apply for the building permit and must sign agreements, covenants or deed restrictions ensuring the principal dwelling or apartment remains the domicile of the owner-occupants with no seasonal occupancy, that the apartment or any interest in it is never sold apart from the whole residence, and that tenant income and lease documentation is produced to the Building Department or Director of Housing on request.

A rental permit under Chapter 270 is a separate prerequisite before anyone can occupy the unit, and apartments approved after January 1, 2019 must also show the rent does not exceed the Suffolk County fair market rent set by HUD. Because occupancy, ownership share and permit eligibility are all tied together, a change in who lives on the lot can put an existing accessory apartment out of compliance.