Southampton Village, NY Building Safety: Anti-Mansionization (2026)

Section 116-17.1 of the Southampton Village Code is the village's answer to oversized houses. It applies in the R-120, R-80, R-60, R-40, R-20, R-12.5 and R-7.5 Residence Districts and the MF-20 Multi-Family Residence District. Subsection E sets the formula: 10% of the lot area, plus 1,500 square feet, less the total gross floor area of accessory buildings on the lot. Every square foot placed in an accessory building comes out of what the dwelling can have. Subsection C adds an absolute ceiling: whatever the formula would permit, the aggregate gross floor area of all buildings on a lot cannot exceed 18,000 square feet.

What counts matters as much as the limit. Gross floor area is the total gross horizontal area of all floors measured to the exterior of the outside walls, including the floor area of an enclosed breezeway-type structure that is part of the dwelling and of any enclosed porch. Subsection A excludes the floor area of a cellar. A half story is excluded only to the extent that it has a ceiling height of at least seven feet over not more than 1/3 of its floor area, and the portion above that third is counted. Floor area under a roofed porch, deck, patio or balcony attached to the dwelling is excluded as long as the structure is not enclosed so as to be habitable space. An attached garage is excluded up to 260 square feet in districts requiring 20,000 square feet of lot area or less, and up to 400 square feet in districts requiring more than 20,000 square feet. Under Subsection B, a room with a ceiling height over 16 feet has its floor area doubled.

Detached garages get a larger exclusion under E(1): 520 square feet in the smaller-lot districts and 800 square feet in the larger-lot districts, and only for a detached garage without any living area. A lot that uses the detached-garage exclusion loses the attached-garage exclusion under E(2), so the entire floor area of a garage that is part of the dwelling is counted. Subsection D requires the calculation to be certified as correct by a New York State licensed architect, professional engineer or surveyor. The section was added by L.L. No. 3-2003 and most recently amended by L.L. No. 16-2024 on 4-23-2024. Section 116-37A(2)(b) ties it to permitting: no building permit is issued unless the plans conform in all respects to Chapter 116.