The Dough on NYC Sky Exposure Planes

ZonerApp
ZonerApp
Nov 27, 2017 · 4 min read

The ‘dough’ in the sky of NYC real estate development is typically how much total floor area a zoning lot or assemblage of lots will allow according to the New York City Zoning resolution. Answers to development questions are not ‘cut and dry’ because decisions must be made on interpretations of the mammoth 3,917 page document.

This development process can be extremely confusing especially when teams increase in size. There are at least 150 different design decisions or variables defined by the NYC Zoning Resolution that effect a typical building enclosure. In a development each one of these variables can have a dozen or more possible interpretations and possible zoning solutions. Getting everyone to agree on this titanic set of rules, including the regulating authorities is an immense challenge.

Project concurrence on just one variable is difficult and time consuming. In this post we will attempt to explain the challenges illustrating the sky exposure plane variable.

If you happen to visit the NYC Thanksgiving Day Parade on 6th Avenue and the midtown streets, you may notice that midtown building silhouettes against the western sky are nearly exact inversion of their own stepping geometry rising from the street to the sky. It is interesting, but how did the shape of this dramatic composition come to be?

The shape of this part of the city and most everywhere else you look in New York City is a direct relationship to the building setback regulations. Setback regulations force developers to push their buildings away from the street as the buildings grow in height, similar to the tiers on a wedding cake. Setbacks were mandated to ensure that streets didn’t suffocate between parallel rows of vertical towers and that sunlight and air could make its way down to the ground.

The imaginary construction line that define these building setbacks is called the sky exposure plane. The sky exposure plane begins at a distance at or above the ground floor plane and slopes away from the street.

Since sky exposure planes relate to increasing amount of light that reaches streets the slope of the sky exposure plane depends on the width of the street.

A “narrow street” is any #street# less than 75 feet wide.
A “wide street” is any #street# 75 feet or more in width.

Therefore wider streets allow for a steeper slope and narrow street have a shallower slope that setting the building bulk back further so more light can reach the street.

The slopes are calculated from the zoning table below and the zoning resolution provides a nice graphic to explain the variable slopes between wide and narrow streets.

The table above introduces other terms such as #street line#, #initial setback distance#, and front wall, which are terms that are important to an accurate zoning analysis in themselves but for the moment we will stay with explaining the sky exposure plane variable.

At this point our research into the sky exposure plane variable is done by referencing at least three different data sources for information. The first is the lot location the second is the street width and the third is the zoning resolution. In the zoning resolution you must determine the zone and then reference the table above to determine the slope of sky exposure plane.

Most people are confounded by the dozens of zoning resolution terms that have bearing on sky exposure planes and find it necessary to hire an architect , surveyor, and a lawyer for a correct interpretation.

Thanksgiving Day and the Macy’s parade is an amazing celebration of human capital and it is also a time of civic reflection. There are complex factors taking place to shape the city backdrop for the dreamy parade floats. We should be thankful to the balance of city government and private investment for allowing city dreams to become reality. On the good side, the city’s complexity, and the code is a tool through which creative architects and developers can identify smart investments, differentiate properties, and create value.

“Stay hungry, stay foolish.” — Steve Jobs

To learn more about sky exposure planes, getting them right, and float through the maze of city development like the ‘Dough Boy’ please checkout www.zoner.city.

with gratitude written by March W. Chadwick

ZonerApp

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ZonerApp

Zoner lets you create your own building on any site in New York City. It is as easy as querying a building address! Try it out — http://zoner.city.

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