Hidden Housing

The interactive map is a tool that enables policymakers to assess the impact of a conversion program on a neighborhood and to site possible pilot programs.

December 5, 2017 - by Dillon Massey - 


The interactive maps bridges the gap between the research and the impact, or implementation, of the results of the project. We worked closely with Carto, the platform on which the map is based, to produce a custom map with interactive components. The map shows the distribution of potential basement apartments by 2010 Census Tracts. The larger dots show the greatest concentrations of potential basement apartments. The orange areas have the least onerous parking requirements.

Applying our “Five Filter” system, we estimate that a program to facilitate basement conversions could generate between 10,000 and 38,000 new apartments across New York City. This range represents basement apartments that can be built as-of-right, meaning that their creation is not contingent on changes to or special waivers from the Zoning Resolution. Mapping these results helps identify potential-rich regions of the City suitable for a pilot program to test code reforms, technology, and incentive programs that support conversions.

The lower boundary of 10,000 units represents basements in single-family homes outside of a floodplain that do not require additional parking. This number is likely to be considerably larger given parking exceptions for conditions that could not be calculated on a city-wide scale for this analysis. The upper boundary of 38,000 units represents the same set of eligible basements plus those that would be eligible absent current parking requirements. In practice, some of these basements may not be convertible if an additional off-street parking space cannot be accommodated. However, field visits to neighborhoods of the city where large numbers of viable basements fall within a required parking zone revealed that many of these lots are either eligible for a parking exemption or can accommodate a second on-site parking space.