America needs more homes in the right places. That means fixing zoning.
There’s a lot to like about the bipartisan 21st Century ROAD to Housing Act, which became law in July. It curbs institutional investor control over housing, reduces construction costs for manufactured housing and develops pilot programs for home repairs, small-dollar mortgages and housing conversion grants. It also positions the federal government to influence zoning codes, the local rules that dictate what gets built where. Among other things, the Act directs the Department of Housing and Urban Development (HUD) to set up two grant programs for states, regional agencies and local governments to tackle zoning reform. But Congress left out a key part: requiring that these grants actually result in more housing.
For planning and implementation grants, for example, the new law outlines fundable activities in very general terms, including increasing the amount of available housing, reducing barriers to housing development and updating zoning codes. For “innovation fund” grants of up to $10 million, the law would reward localities for initiating zoning reforms like “increasing by-right” multi-family housing and “revising minimum lot size requirements.” The law does not, however, establish how far an applicant must go in order to receive these grants. Without high, measurable benchmarks, American taxpayers stand to waste tens of millions of dollars on window dressing. HUD, the federal housing agency implementing the law, needs to write ground rules that hold grant recipients accountable for reforms that actually create housing.
HUD’s challenge is that zoning is complicated. In fact, it’s the most complicated regulatory area in the American legal canon. Fifty state legislatures authorize more than 33,000 local jurisdictions to zone. The fragmentation of zoning across these jurisdictions, and the complexity of zoning codes, has created an information gap. No one has ever calculated how many localities zone, much less what their codes say.
Furthermore, few understand how all the regulatory levers of zoning work together. My research shows that jurisdictions zone by a thousand cuts, creating hidden barriers to housing. A city that permits apartments, for example, might look good on paper. But if the zoning code requires proposals to undergo public hearings, which are often attended by existing residents who object to new housing, those apartments might never be built. Such projects may also fail to pencil out when the zoning code caps building heights, requires oversized lots or mandates too many parking spaces. These are just some of the many restrictions that HUD needs to root out in its implementation of the 21st Century Road to Housing Act.
As a starting point, HUD can consult a free public resource that begins to fill the information gap. The National Zoning Atlas, which I helped build, enables nonpartisan, apples-to-apples comparisons of zoning codes where two-thirds of Americans live. Our team has standardized the inconsistent, technocratic and convoluted language of over 1.2 million pages of zoning texts, and we’ve digitized zoning maps, many for the first time. To ensure we can calculate prevailing regulations, we have developed a unique process of creating “slices” that merge base zoning districts with any applicable overlays (which can sometimes modify base-district rules). The resulting interactive atlas reveals how different rules apply to more than 90 million parcels across the country. Also available are summary snapshots summarizing the percentage of land allowing single-family housing, apartment, small-lot housing and mixed-use developments, among other things — for each jurisdiction, county and metropolitan area.
A close look at National Zoning Atlas data confirms that, contrary to those who see Congress as sticking its nose where it doesn’t belong, intrusion is necessary: Jurisdictions thwart affordable, accessible housing in far too many ways. At a basic level, they eliminate the number of units that can be built on any given parcel. Across the jurisdictions in the Atlas, which covers two-thirds of the country’s population and acreage, 81% of residentially-zoned land is devoted to single-family housing only, mostly on huge lots of an acre or more. Even in cities, just 29% of residentially-zoned land permits four-or-more-family housing by right; that figure drops to 9% in the suburbs.
Beyond number-of-unit zoning, the Atlas also documents the significant extent to which jurisdictions require public hearings, parking, minimum lot sizes, setbacks, floor-to-area ratios, lot coverage caps and height caps that can make new housing infeasible. All of these data points, assembled at scale for the first time, can be analyzed against parcel boundaries to identify exactly how much housing can be built within a jurisdiction under current zoning rules.
Atlanta’s zoning code illustrates just how important it is to understand how all of these rules work together to influence housing production. On the surface, the City appears moderately permissive, allowing four-or-more-family by right on 30% of residentially zoned land (right at the national average). But a closer look at the code reveals that myriad dimensional and developmental constraints on apartments are buried in nearly 900 pages of zoning text. Other types of housing are also restricted: A quarter of single-family land has minimum lot sizes of a quarter acre or more, and more than half of single-family land prohibits accessory dwelling units. My suspicion is that a new draft code would likely make this all worse, with a more bloated text and more complex regulatory approach than the status quo. If the City moves forward, we will geocode any adopted reforms and calculate whether they actually enable more housing.
HUD has shown no great interest in undertaking similar before-and-after calculations itself. A $50 million HUD competition now open, for example, offers grants for “enactment or implementation of less restrictive zoning” rules that increase capacity for housing. But the program does not specify how to calculate zoned capacity. And HUD doesn’t seem to require independent verification of jurisdictions’ calculations. These types of measurements are crucial to understand the effectiveness of federal interventions intended to shape zoning.
A cautionary tale for HUD comes out of Massachusetts, where the bipartisan MBTA Communities Act, adopted in 2021, required 177 communities in the Boston area to rezone an area around their transit stations for multi-family housing. Our analysis of zoning before and after the change found that only 1% of land was rezoned as a result of the statute, with at least some of that land highly unlikely to ever see an apartment because of its configuration or current usage. Even when a developer finds a rezoned parcel suitable for development, she will often run up against the “thousand cuts” that localities have stubbornly maintained on rezoned land. Perhaps the legislature would have more to show for the tremendous amount of political capital used to pass and implement the law if members had established specific, ambitious benchmarks — at a minimum, the percentage of land required to be rezoned.
That’s what I hope HUD understands as it sets up these new zoning-related grant programs. While zoning can be tricky, measuring regulatory change is now possible at scale. For federal intervention in zoning to make a difference, policymakers must understand what it will take to achieve meaningful increases in housing supply.
