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Digital Atlas Reveals Zoning’s Impact on Affordable Housing

There’s increasing evidence that low-density zoning codes can restrict the nation’s housing supply, but it’s not easy to see how this plays out in every community. A national atlas of zoning codes could help change that.

Aerial view of single-family homes under construction.
Single-family homes under construction. Zoning codes that favor such structures over multifamily housing constrain housing supply.
(Xavier Mascareñas/TNS)
Last month the median list price of a home in the U.S. reached $425,000. This record high may not hold under the pressures of inflation and rising mortgage interest rates. But even if it dropped by $100,000, the housing affordability pyramid from the National Association of Home Builders shows that more than 6 in 10 households would still be priced out.

At the same time, rent has been increasing at a record pace, up an average 11.3 percent in 2021 and three or four times as much in some Sun Belt communities. More than 17 million households in America — about 1 in 7 — now spend half or more of their income on housing, Habitat for Humanity’s CEO Jonathan Redford said recently.

The National Low Income Housing Coalition (NLIHC) estimates that the country has a shortage of 7 million rental homes for low-income renters alone, almost 1 in 4 of all rental households. There is no state in the U.S. where a worker with a full-time minimum wage job can afford a two-bedroom rental — in Arizona, which ranks 19th among states with the highest housing/wage ratio, a worker paid $22 an hour would still need to work 73 hours to afford such housing.

The pressure to increase the supply of housing priced within the means of working Americans has never been greater. Setting aside a current shortage of building materials and construction workers, the fundamental solution is straightforward: build more housing that can be priced within the reach of working Americans.

In most communities throughout the country, however, zoning laws create obstacles to building new housing. Taking lessons from a project launched in Connecticut by a Cornell professor, academics, nonprofits, attorneys and local officials are working to create a national zoning atlas that can bring these stumbling blocks into plain view.
David Peery, founder of the Miami Coalition to Advance Racial Equity, speaking at a rally protesting high rent.
David Peery, founder of the Miami Coalition to Advance Racial Equity, leads a rally against high rent. Rent increased as much as 40 percent in some Florida communities in 2021, according to the real estate researcher CoStar Group.
(Carl Juste/TNS)

A Tool for Storytelling

Sara Bronin, a professor in Cornell’s City and Regional Planning department, lives in Hartford, Conn. Responding to calls for racial equity that arose in the aftermath of the death of George Floyd, in 2020 she founded the nonprofit Desegregate Connecticut (DesegregateCT) to help increase housing diversity and supply.

Bronin led a team of students, planners and community members that collected zoning codes from every jurisdiction in the state. This work encompassed more than 2,600 zoning jurisdictions in 169 municipalities and 11 submunicipal districts. The team organized and analyzed the code data and combined it with GIS data to create an interactive map that shows how housing is zoned in every jurisdiction in Connecticut and includes overlays showing transit stations, waterways and sewer service.

The results have been illuminating. “Ninety one percent of Connecticut is zoned for single-family housing,” says Bronin. Only 2 percent is zoned for multifamily housing “as-of-right,” with no requirements for approval or special conditions.

The atlas has been a change agent, according to Peter Harrison, the director of DesegregateCT. “If you want to change public policy, you need to be a storyteller, and the atlas is an incredible piece of storytelling.”

The interactive map enables users to zoom inward to the local level to see what is allowed and what is not, and zoom outward to see similarities and differences in statewide regulations.

“You click and change from single-family housing allowed as-of-right to multifamily as-of-right, and the map goes blank — the story we’re trying to tell becomes real at a scale and speed that we could not do without it.”

As part of its map project, DesegregateCT created a playbook that others could use to make their own zoning atlas. From her lab at Cornell, Bronin is leading an effort to create a national zoning atlas, with collaborators including the Urban Institute.
Screenshot of two maps side by side from the Connecticut Zoning Atlas.
Maps from the Connecticut Zoning Atlas reveal the extent of restrictions on multifamily dwellings in the state.

Democratizing Zoning

Connecticut has the only statewide atlas that has been completed to date, but projects are already underway in California, Hawaii, Massachusetts, Montana, New Hampshire, New York and Ohio. Partners include universities, government housing departments and nonprofit organizations. Bronin is recruiting participants in every state.

As state atlases are completed, they will be integrated into the national version; some teams may also publish state-level atlases. “We’re distilling the key characteristics of zoning codes into a format that people can understand easily,” says Bronin.

This will help researchers who want to understand zoning’s impact on housing, education, environmental quality, climate change, transportation patterns, the economy and even government finances. People deserve to understand how government works, Bronin says, and zoning is one of the most important powers of local government.

As the atlas grows, it will become possible to compare regulations from state to state, yielding insights that could improve both state and national housing efforts, says Yonah Freemark, senior research associate at the Urban Institute and research collaborator for the national atlas. “Zoning rules intersect with the real estate market, with the housing market, and the way that intersection works is something we don’t fully understand right now.”

In some Midwest cities, zoning that would allow extensive construction is matched with a nonexistent housing market, says Freemark. If San Francisco had the same zoning allowances as the South Side of Chicago, it would see significantly more construction. “It’s really important to get a clear sense of how those kinds of differences play out, and why the same zoning matters in some places and not others.”
An accessory dwelling unit under construction in a Los Angeles backyard.
An accessory dwelling unit under construction in a Los Angeles backyard. Lifting restrictions on such structures can boost affordable housing supply in residential neighborhoods.
(Dania Maxwell/Los Angeles Times/TNS)

A Form of Self-Strangulation

Every community wants to limit what can be built in it, says Max Latona, executive director of the Center for Ethics in Society at Saint Anselm College. “They say, ‘If we need more housing, let’s let another community do it’; the result is that the buck keeps getting passed and nobody’s building the homes that need to be built.”

Latona is the director for the New Hampshire statewide atlas, with partners including the state’s Office of Planning and Development (OPD) and the New Hampshire Housing Finance Authority. “Zoning can help a community decide what kinds of homes are built and where they are located, but when it becomes overly restrictive it’s really a form of communal self-strangulation,” he says.

Although zoning is recognized as a barrier to development, statewide data about what’s allowed and what is not isn’t readily available, says Noah Hodgetts, principal planner for OPD. The atlas will be valuable for developers as well as policymakers, says Hodgetts, speeding and improving research about what kinds of projects are allowed.

It will also promote understanding differences in zoning in tightly packed New England communities, he says. “Right now, there’s really no congruence between communities; you can go from half-acre zoning to five-acre zoning just because you crossed a municipal boundary.”
A screenshot of Montana’s zoning atlas.
More than half the residential land in Montana’s largest city is zoned for single-family homes.
(Frontier Foundation)

Zoning and Freedom

The nonprofit Frontier Institute is compiling an atlas for Montana. So far, it has collected data for six cities, with plans to eventually include 13 to 14 counties and the cities within them.

Affordable housing has become a problem in the state, with an increase in remote workers leaving New York and California for big skies and, hopefully, cheaper housing. Instead they are experiencing sticker shock. The median price of a home in Bozeman is $850,000, says Kendall Cotton, CEO of the Frontier Institute. Statewide, the typical price is over $400,000, up 28 percent over the previous year. Housing costs have gone up so much that businesses that want to expand are losing employees because they can’t afford to live in the state.

Cotton and his team collected data, and the foundation contracted with a planning professional who had served on Bozeman’s planning board to organize it and help create an interactive map.

Since the institute created the map a couple of months ago, they’ve had a tremendous response, according to Cotton. “It’s been a really interesting experiment because this is a policy area where the typical left-right divide just doesn’t seem to hold up.”

Stakeholders on the left see the social justice aspects of reforming zoning codes, and those on the right want to remove governmental barriers for builders and residents who want to find homes, start families and build strong communities. City leaders and state legislators from both parties have shown interest in findings and recommendations that have come out of the atlas, says Cotton.

“The hope is that city council members and local governments will embrace the idea that relaxing local zoning codes and giving landowners freedom to build homes where they’re needed — smack in the middle of cities — is completely within their power to do right now.”
Aerial view of a Southern California suburb.
A Southern California suburb. Zoning favoring single-family housing has fueled development that places unsustainable demands on local resources.
(Robert Gauthier/TNS)

Falling Short

Attorney Sean Suder has worked on zoning code projects in 13 states and served the city of Cincinnati as chief counsel of land use and planning. He founded the consultancy ZoneCo to assist local governments in creating zoning and land use practices that advance racial, social and economic equity.

ZoneCo is creating an atlas for Ohio. “Nobody has ever done a comprehensive inventory and analysis of residential zoning laws in the state of Ohio,” says Suder. “I don’t think we even have an inventory of how many zoning codes there are.”

Suder sees this data as an important tool for his equity work. He’s hired three Cornell students for the summer and beginning on June 6 they’ll help his staff go through housing codes that are in place in about 240 cities, 88 counties and 1,300 townships. “Some portion have codes, and some don’t, so we’re estimating that they’ll be going through 600 to 800 zoning codes.”

The data will help the state see where it’s falling short in terms of allowing for multifamily housing and housing density. Not every citizen wants a single-family home, Suder says, the costs associated with maintaining it or the transportation expenses that can come with getting to and from it.

“I think that when federal leadership sees a national zoning atlas and sees what percentage of our country is constrained it’s going to be eye opening. Hopefully it will be a tool to make legislative changes at the national level as well as state and local levels.”

Teaching and Engagement

The website for the national zoning atlas project includes guidance for those who want to be a part of it, with tips for putting together a team and a 90-page guide covering protocols for data collection, analysis and map creation. It’s intended to be a clearinghouse for information and for people who want to develop projects or join project teams, says Bronin.

Atlas teams can also join the project’s research collaborative. In exchange for committing to data accuracy, seeing data collection to completion and collaboration, they receive access to meetings, group conversations, connections to potential funders and inclusion of their data in an integrated, interactive national map.

“We think that the atlas can be an incredibly important teaching tool,” says Bronin. “Our hope is that we’re laying the groundwork for many different people to use this information to guide decisions and also to engage people in the process of planning.”

It’s not the norm for local zoning decisions to be based on data, says Sean Suder. “They’re usually made based on all kinds of different factors — politics, individual interests, economic development issues, whatever the issue of the day is.”

“This project gives local government officials a resource to make data-driven decisions around zoning for housing. If it’s used right, that’s going to be very powerful.”


Carl Smith is a senior staff writer for Governing and covers a broad range of issues affecting states and localities. He can be reached at or on Twitter at @governingwriter.
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