See how your state uses zoning codes to control land use

More than 22 million households now spend over a third of their income on rent, and home prices are higher than they’ve ever been. In a survey from the real estate company Redfin, the most important issue listed by Generation Z voters wasn’t the economy or immigration or reproductive rights. It was affordable housing.

None of this comes as a surprise to state and local leaders, who have been scrambling to address a shortage of housing that one estimate puts at 4.5 million homes. For the first time in its 11-year history, the State of the Cities report from the National League of Cities found that housing was one of the top three themes of mayoral addresses this year. And state lawmakers passed major housing bills in Colorado, Delaware, Maryland, Massachusetts, New Jersey and New York that, among other things, updated zoning codes and transformed residential planning processes.

Now a newly expanded online tool is making it easier to understand how communities use zoning to control land use.

By “digitizing, demystifying and democratizing” zoning codes, the National Zoning Atlas seeks to provide a more comprehensive understanding of what a state’s zoning landscape looks like, Sara Bronin, the project’s director, told Route Fifty last year.

Since Bronin spoke with Route Fifty, the project has expanded rapidly. Last week, the project announced the launch of the Arizona Zoning Atlas. Roughly 36 states have been mapped, some in their entirety and others just in certain metro areas or jurisdictions. At the beginning of the year, the National Zoning Atlas released a public map that shows everywhere there is published data. Nevada and New Mexico are on their way to completion, as are major metro areas in Colorado, New York and North Carolina, according to Diana Drogaris, outreach coordinator for the National Zoning Atlas.

“All the geographies published cover just under 100 million people,” said Drogaris in an interview with Route Fifty. 

Launched in 2022, Drogaris says that one of the ways she has seen the maps most commonly used is for messaging. “People love comparing themselves,” she said.

Indeed, the online, interactive maps allow people to compare zoning codes in cities and towns in a state. The maps show where single-family housing, multifamily apartments and accessory dwelling units can be located, as well as where lot sizes, parking requirements and height caps influence development.

In Vermont, the state Department of Housing and Community Development used the map in a lecture series earlier this year to highlight the need to reduce lot size requirements. Vermont has the largest lot sizes in the U.S. at an average of 1.8 acres. State officials used the Vermont Zoning Atlas to show residents how most Vermont towns disappear from the map when a user selects for areas where single-family homes are allowed on lots less than one-quarter acre. The requirement for building on large lots, Amy Tomasso, a project manager at the department, told the audience, increases sprawl and car dependency, and creates neighborhoods that are less welcoming for a diverse range of people.

One of the goals of the initiative is to reveal the role of zoning codes on social problems.

“We've used zoning to restrict opportunity, slow economic growth and destroy our environment,” Bronin said last year. “I think once people realize that that is the consequence of zoning as we have it, they will be much more willing to change it. In fact, they'll feel an imperative to change it.”

Another is to help policymakers confront the housing supply crisis that is rippling across the country. 

In Montana, the statewide zoning atlas that went live last year helped inform a slew of housing bills. Researchers with the Montana Zoning Atlas worked with a statewide housing task force to help lawmakers craft legislation to address the state’s housing shortage. The new laws ease regulations on duplexes and accessory dwelling units, create new requirements for local governments to update policies to meet projected demand, and limit parking requirements. 

The learnings from mapping Arizona could help with housing legislation in the state, where earlier this year Gov. Katie Hobbs vetoed legislation that would have restricted how local cities regulate home designs and single-family home lot sizes.

In mapping Arizona’s 106 jurisdictions, geospatial specialists have learned that 94% of the state’s land zoned for residential uses allows for single-family housing, and just 20% allows for multifamily housing. Additionally, 95% of land zoned for residential uses has minimum parking requirements, and 88% of land zoned for single-family housing has a minimum lot requirement of 1 acre or more. Housing experts say those types of requirements constrain the amount of housing that can be built on a lot and contribute to suburban sprawl. 

Beyond the interactive maps, Drogaris says the National Zoning Atlas is now releasing snapshots that summarize zoning in large metro areas.

Drogaris noted that the tool is in its early stages and that the initiative is partnering with other organizations on several projects, such as the Urban Institute to look at sea-level rise and the Regional Plan Association to try to quantify “a climate change housing deficit.”

“We are at the beginning stages of the data being activated,” she said. “We’re all starting at ground zero, and [working toward] smarter, more inclusive planning.”