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

Section 330-84D(1)'s Pyramid Law applies to all lots in the Town outside the villages except those in the Village Business, Office, Hamlet Office/Residential, Hamlet Commercial/Residential, and Light Industrial (LI-40 and LI-200) Districts. On covered lots, buildings and structures must remain inside a sky plane that begins at each property line at the average elevation of the existing natural grade adjacent to the structure and extends inward at a 45 degree angle. The average grade is fixed using spot elevations under NAVD 1988, taken before any site disturbance at the two outermost points along the facade wall nearest the street, on a plan prepared by a New York State licensed surveyor or engineer, with the pyramid line then drawn inward from all four property lines.

Critically, the sky plane does not create extra headroom: § 330-84D(1) states that notwithstanding the formula, the maximum height set in the dimensional tables at §§ 330-11, 330-34 and 330-38 still cannot be exceeded at any point, unless the structure is exempt under Subsection A or under D(2)(a). A parallel rule in § 330-84D(2) applies in FEMA AE or VE flood zones, where the sky plane instead begins at base flood elevation plus required freeboard, with an exception in D(2)(a) letting existing structures in those zones be elevated above the sky plane and above the ordinary height maximum to meet current state and federal flood regulations.