Build on, and build up, public facilities.
During his campaign for mayor last year, Zohran Mamdani focused on housing, emphasizing the importance of adding supply to address the city’s punishing rents. His emphasis responded to a real problem: More than a quarter of city renter households — more than 600,000 of them — spend more than 50% of their incomes on housing costs. An additional 200,000 households that own their homes suffer similar burdens.
In response, Mamdani promised to add 200,000 publicly subsidized, rent-stabilized homes within 10 years, while also increasing “zoned capacity” with the goal of encouraging market-rate development, following in the footsteps of recent large-scale upzonings, like that of Gowanus in Brooklyn. His theory? Adding more housing would make homes more affordable — a concept well supported by reams of research and the real-world experience of cities like Austin and Minneapolis.
One key mechanism Mayor Mamdani recommends using in his recently released housing plan is activating City-owned land — such as parcels that are vacant. Using publicly owned land can reduce overall project development costs and ease approvals. Upon taking office, Mamdani established the “LIFT” Task Force, intended to identify sites appropriate to support 25,000 new homes within 10 years; the task force is expected to release its conclusions by July.
In a city where development opportunities are too few and far between, it makes absolute sense to pick this low-hanging fruit. But vacant lots should be only the beginning. The mayor’s housing plan recommends colocating housing with schools, libraries and other public assets. These sorts of redevelopments, which I refer to as joint developments, enable the financing of new public facilities while making way for housing units on top — a combination that can help address the City’s underfunded facilities needs while providing homes for thousands of New Yorkers.
I conducted a sketch-level analysis, finding that such joint developments of housing plus schools, libraries, police stations and fire stations offer the opportunity to create between 20,000 and 34,000 new housing units over the next several years, equivalent to the total number of housing units added citywide in 2024. Joint developments, which the City has already begun to undertake, could thus be a major tool to generate more homes in the public arsenal.
Recent joint developments in New York City
Joint developments on publicly owned land often involve demolishing an aging facility and replacing it with a new tower that includes a new public service at the base and apartments on top. Across the United States, dozens of libraries have been redeveloped in this way in recent years.
New York City agencies have implemented such joint developments slowly but steadily. Examples of such combinations include:
- The Inwood Library project, completed in 2024: This 174-unit affordable housing tower in Upper Manhattan, which replaced an existing library, includes a library and prekindergarten.
- The Solaire, completed in 2002: This 293-unit apartment building in Battery Park City houses PS/IS 276, an elementary and middle school.
The City is currently in the early phases of additional projects, such as the Bloomingdale Library and Riverside Health Center on the Upper West Side. There, the City has recently solicited proposals to redevelop the site with a new library, community center and up to 850 affordable housing units.
Though New York City has not yet built new police or fire stations with apartments on top, other cities are pursuing this type of joint development. Washington, D.C., is planning to redevelop a police and fire station on U Street. And Miami’s 791-unit Mercedes-Benz Places project, now under construction, will incorporate a fire station.
Opportunities for new joint developments
I sought to evaluate other opportunities available to undertake joint development projects on land now occupied by libraries, police stations, fire stations and schools in New York City. There are many thousands of possible sites.
I leveraged New York City’s PLUTO map data, which I combined with the City’s database of owned and leased properties. I made the following assumptions, which result in conservative estimates of redevelopment potential, but are focused on aging facilities: Joint developments can only occur on land owned by the relevant public agency; buildings that are landmarked, that were constructed since 2000, that have been renovated since 2010 or that have greater than three stories (or two stories for schools) are not candidates to be replaced; and schools’ sports fields would remain in place. Nonetheless, this is a preliminary analysis; I did not review sites individually to evaluate their potential.
I assumed that the maximum development size would be 300 units (small in some New York City contexts!) and that the first floor-and-a-half of any new development would be devoted to the public facility.
My analysis makes two estimates. First, I calculate the number of housing units that could theoretically be built on each City-owned parcel following current zoning allowances for residential construction. Second, I calculate how many housing units could be built if the parcel were rezoned to enable densities at the 90th percentile of current apartment buildings in the community district in which the parcel is located — in other words, if they were built at a scale similar to the neighborhood’s existing environment. This latter figure reflects the fact that current zoning policy may sometimes be overly restrictive.
This analysis found substantial opportunities for joint development throughout the five boroughs, including on sites now occupied by 125 libraries; 144 police department buildings; 188 fire department facilities; and 114 schools. In total, I estimate that about 19,500 housing units could be completed on these sites under current zoning, or about 33,900 units could be completed were sites upzoned to match the density levels of nearby apartment buildings.
Under current zoning, library sites could accommodate about 3,100 units (75% located within a half-mile of a subway station), police department sites 4,900 units (71% near a station), fire department sites 3,300 units (87% near a station) and schools 8,200 units (61% near a station). These figures could increase dramatically, particularly in Brooklyn and Queens, if sites were upzoned to enable higher-density development.
Some illustrative examples include:
- The Queens Library branch at Forest Hills: This two-story facility, completed in 1957, is half a block from a subway station. Current zoning enables roughly 55 units on top of a library at the site.
- The New York Police Department’s 28th Precinct: This two-story building, completed in 1975, is located just south of 125th Street in Central Harlem. Zoning enables 217 housing units on top of a police station.
- The New York Fire Department’s Engine 54: This two-story building, completed in 1974 at the intersection of 8th Avenue and 48th Street in Midtown, could be redeveloped to accommodate 59 housing units.
P.S. 308, an elementary and middle school in Brooklyn: This Bedford-Stuyvesant site, completed in 1972, could accommodate 150 housing units.
Regulatory changes recently adopted by the City, including the Expedited Land Use Review Procedure and the Affordable Housing Fast Track, may speed the implementation of certain projects, especially if they incorporate affordable housing units.
I modeled only projects incorporating libraries, police stations, fire stations and schools. But the City and its sister agencies own a large number of additional aging properties available for joint development. For example, earlier this year, the City Council approved the replacement of a seven-story City-owned office building in downtown Brooklyn with an 80-story tower including 1,263 housing units, many reserved for households with low and moderate incomes.
Trade-offs in achieving joint development projects
The use of publicly owned land can reduce projects’ total development costs. But joint developments cannot accomplish all public goals simultaneously, especially in neighborhoods with relatively weaker housing markets.
Joint developments save developers money compared to what they would pay for land on a privately owned site. These savings could be redistributed to fund the new public facility. But realistically, those savings are unlikely to be adequate to cover the costs of both the new facility and many affordable housing units. To accomplish multiple goals simultaneously, officials may need to combine joint development with other initiatives, such as affordable housing grants, derived from other revenue sources.
Moreover, in weaker housing markets, where developers are less likely to profit from projects, joint developments may produce inadequate revenue even to cover the cost of new public facilities. As such, the City should leverage this tool only if doing so is needed to replace a facility that is in poor physical condition or is in an area in great need of additional housing.
Finally, the redevelopment of existing public facilities, such as fire departments, may cause years of disruption. In many cases, the facility may need to move to a temporary location, which could be expensive. As such, City staff should carefully coordinate construction plans to ensure continued service provision.
Nevertheless, joint development is a major opportunity for cities like New York. The City should work with its sister agencies to quickly advance these projects, which could provide essential housing and new facilities for thousands of residents.
