Urban Wire Four Lessons to Strengthen Land-Use Reforms
Lydia Lo, Owen Noble
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Tiny home

Evidence suggests that land-use regulations are one of the top reasons for America’s housing shortage. In addition to separating industrial and residential land, many zoning laws were designed to deny Black people, other people of color, and low-income people access to the same resources as white and wealthier residents. Undoing these inequitable patterns and reducing America’s housing shortage requires land-use reforms. Although some states, including California, Nebraska, and Vermont, are debating or have passed laws intended to solve those problems, policymakers and planners who set local ordinances don’t have a consistent roadmap for passing or implementing reforms that boost supply.

  • What goes into passing a land-use reform to promote housing?
  • Once it passes, how can cities ensure a reform leads to their desired production outcomes?
  • How can both the process and outcomes support equitable benefits for residents?

We investigated these questions through case-studies in two cities—Washington, DC, and Portland, Oregon—that reformed their land-use laws to allow more accessory dwelling unit (ADU) production. ADUs, which are smaller residences on the same lot as, or within, a single-family home, are generally less expensive than other unsubsidized rental units, and they are usually developed by homeowners.

Did land-use reforms in Portland and DC boost housing production?

Both Portland and DC experienced a 24 percent increase in population between 2000 and 2019 and needed to provide more housing within their rigid borders.

In 2010, after 12 years of reforms to Portland’s ADU code, the city council passed a waiver of all infrastructure fees for ADUs, which preceded a 600 percent increase in annual ADU production to 632 units in 2018.

DC spent nine years on intensive public engagement to pass a large-scale zoning regulation review package in 2016 that included a provision to allow ADUs. Before the reform, ADU production stood at roughly 1 unit a year, but following the reform, it increased to an average of 23 ADUs a year.


New ADU permits in Portland, OR, and DC from 1995-2019

How to make the most of land-use reforms

We found that Portland’s ADU reforms passed more easily and had greater impact on housing production than DC’s because of the city’s different local contexts and approaches. Based on these findings, here are four lessons for elected officials, planners, and advocates working on zoning reforms to deliver more housing.

  1. Establish shared and coherent urban planning goals
    Planners and city officials can smooth the way for reforms in constrained housing markets by building coherent comprehensive plans that facilitate and encourage urban density. Oregon legally required Portland to keep new construction within an urban growth boundary to preserve nature, and as a result, the city’s comprehensive plan prioritized urban housing density. These well-documented and widely supported priorities made it easy for the city council to pass their ADU zoning reforms.

    In contrast, DC’s 2006 comprehensive plan contradicted itself by prioritizing preservation of low-density development and increased housing production within a fixed space. It also lacked any regional government with land-use oversight to encourage density. Consequently, the zoning regulation review process had to continue the contentious debate between residents and city officials about what the city should look like, which took years to resolve.
  2. Analyze volunteer participants’ economic and racial composition and supplement their input (as needed) with data to ensure representative decisionmaking
    In both cases, residents who volunteered to participate in zoning reform hearings (by submitting comments and testimony) did not represent the demographic or economic makeup of the city. Participants tended to live in neighborhoods with higher shares of white, wealthy, and homeowning residents than the rest of the city.

    In Portland, planners and voting officials reviewed the commenters’ economic and racial makeup and, in finding these did not represent the city well, instead based their decisionmaking on more representative, supplementary survey data.

    In contrast, DC’s process heavily emphasized residents’ input, even though the vast majority of participants came from wealthier wards. Decisionmakers gave roughly equal weight to supportive and opposing comments and added expensive restrictions to the reform that only 27 percent of commenters (almost entirely from wealthier wards) requested.

    To avoid these pitfalls, planners and voting officials can weight voluntary participant input according to how well it represents the broader city, supplement with additional data (such as surveys, focus groups, or independent studies) from underrepresented communities, and vote in a way that best advances the city’s housing plan (which already benefited from resident input).
  3. Reform regularly as new evidence emerges
    Portland improved its ADU code to the point where homeowners could easily build ADUs that fit their neighborhoods’ character. Officials accomplished this by regularly revising the zoning code based on production data mixed with resident feedback. According to one planner, “The thing that was interesting and perhaps beneficial was that people would say the sky would fall and the sky didn’t fall. Most people’s neighborhoods didn’t change.” Between 1998 and 2010, Portland reformed the zoning code four times to incrementally adjust occupancy requirements, garage conversions, and lot size requirements based on monitoring studies and homeowner input, and these reforms resulted in a rough average 34 ADUs per year. Although DC’s current ADU production following its reform has averaged just 23 units a year, Portland’s example suggests this figure could increase if, over time, the city makes additional, incremental improvements to its code.
  4. Strengthen other housing system supports
    Zoning is just one piece within the complex, multistakeholder housing production system (PDF), so reforms should take a systems approach. Portland’s reforms were packaged together with adaptations to the building codes, financing products, and public education efforts that helped increase production over time. In contrast, housing advocates in DC lament that the city’s ADU code has not produced many units because other factors (the zoning code, building code, financing products, and other resources) are not aligned to support homeowners in constructing ADUs. Planners and policymakers can streamline the development process to reduce costs and risks, which, in turn, can result in more affordable units and allow low-income residents to benefit.

Zoning regulations affect the amount of housing local markets can produce. Even if a reform raises that cap and increases production, not every reform will yield benefits for all residents. Planners have a responsibility in their code of ethics to prioritize the needs of vulnerable residents and to craft land-use laws that embed racial and economic equity into their content, their process, and the other supports paired with the policy. However, the standard zoning reform process hasn’t traditionally created these outcomes. Planners and policymakers have to reimagine how they pass and implement reforms. 


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Research Areas Neighborhoods, cities, and metros Land use Housing
Tags Homeownership Housing affordability Land use and zoning
Policy Centers Metropolitan Housing and Communities Policy Center
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