Sky exposure plane

A sky exposure plane is an imaginary inclined plane, defined in § 12-10 of the Zoning Resolution, that begins at a specified height above the street line and rises upward and inward over the zoning lot at a district-specified slope. Buildings subject to it may not penetrate the plane except for permitted obstructions. The device protects light and air at the street: near the sidewalk the plane is low, forcing the building to set back as it rises — the geometry behind New York's stepped 'wedding cake' towers.

Sky exposure planes typify the height regime of older, non-contextual districts; contextual districts generally use fixed base and maximum building heights instead. Which regime governs a lot is a first-order fact for any massing or buildability analysis.