New York City Mayor Zohran Mamdani is leaning on land the city already owns to chase a decade-long target of 200,000 new affordable homes.

He is betting that converted libraries, surplus parking lots, and stacked civic buildings can deliver tens of thousands of below-market apartments.

Mamdani's housing blueprint, called "Block by Block," sets a goal of 200,000 new affordable homes and 200,000 preserved units over 10 years, backed by a $22 billion capital plan over five years.

The strategy pairs direct construction with new financing tools and a sweeping land-use overhaul intended to speed production across all five boroughs.

A central piece of that push runs through City Hall's real estate holdings.

On Jan. 1, Mamdani created the Leveraging City-Owned Land to Accelerate Housing, or LIFT, task force, charging it with identifying municipal sites capable of supporting at least 25,000 new homes over a decade.

About 10 projects are already in planning and development, according to Business Insider, with the administration eyeing conversions of underused civic buildings and parking lots.

The opportunity is real but uneven.

An NYU Furman Center analysis of city-owned and leased parcels found roughly two-thirds are already zoned for residential use, while a similar share are substantially underbuilt relative to their allowable floor area.

Only about 16% of lots, however, are both larger than 5,000 square feet and zoned residential, and 34.4% sit under the Parks Department, suggesting active use as parks, open space, or sports facilities.

Jake Krimmel, a senior economist at Realtor.com, told Business Insider that public land is "not a silver bullet," citing zoning rules and irregular parcel sizes that limit the amount of buildable space.

He suggested that the city consider stacking housing atop civic buildings and weighing sales to private developers under affordability requirements.

"The city has valuable assets on its books," Krimmel said, per Business Insider. "The question is whether it deploys them by building itself or whether it attaches affordability requirements, upzones, and lets other developers carry the financing and operations."

The stakes are high.

A majority of New Yorkers spend more than 30% of their income on housing, the standard threshold for unaffordability, and new market-rate apartments now lease for roughly $3,000 a month, nearly double the citywide average of $1,650.

To meet its targets, the administration projects annual production will scale from about 14,000 affordable homes in fiscal 2027 to more than 21,000 by fiscal 2031, an output level that will require buy-in from the City Council, Albany, labor, and private developers.