A gravity-defying monolithic stair anchors the interior of this private Sag Harbor residence. Crafted from Danby Fantastico marble sourced from Vermont, this bespoke, three-flight staircase is the first post-tensioned stone stair of its kind in the United States, merging timeless material with advanced structural engineering. Rising through three levels of living space, the stair transforms everyday circulation into a sculptural, light-filled experience that reflects the historic charm and coastal elegance of this storied Long Island village.

Each of the 50 marble treads—some weighing up to 770 pounds—was meticulously modeled to conceal post-tensioning cables, integrated LED lighting, and glass guard anchorage within the stone profile itself. The result is three distinct expressions of “floating” elegance, achieved through precise geometry, optimized stone cross-sections, and carefully choreographed installation. From concealed anchorage systems to seamless integration with surrounding architecture, the stair exemplifies the fusion of craftsmanship, material innovation, and engineering rigor.