Proposals to eliminate zoning districts that permit only single-family homes have dominated zoning reform discussions for the past five years. But focusing narrowly on getting rid of, so called, single-family-only zoning is unlikely to dramatically increase the supply of housing in most communities.
As John Zeanah, AICP, points out in the May issue of Zoning Practice, "Beyond Use Zoning: The Role of Deregulation in Housing Equity," use zoning, or the component of zoning that establishes permissible uses, is only one method to affect what and where housing gets built. In this issue, Zeanah examines how loosening other development regulations can support missing middle housing and promote housing equity.
Rightsizing Bulk Standards
Permitting different types of residences in a zoning district won't have much of an effect on housing supply if the district dimensional standards make it infeasible to build different types of housing. This is certainly not an original observation, but it remains the area of greatest opportunity for most communities.
In 1991, the Advisory Commission on Regulatory Barriers to Affordable Housing submitted its landmark report, Not in My Backyard, to HUD Secretary Kemp. The report noted that zoning standards that exceeded what is necessary to ensure health, safety, and welfare added about 10 percent to the price of a home. And subsequent research further quantified that excessive lot-size requirements alone accounted for nearly three-quarters of this price premium.
Zeanah suggests planners should evaluate opportunities to relax bulk standards that make it difficult to fit multiple residences on a lot as well as those that require larger lots than the market would otherwise provide. These include standards that stipulate a minimum lot size or lot area per dwelling unit and those that establish a maximum building height.
Revisiting Building Codes
Zoning isn't the only species of development regulation that can make it hard to build missing middle housing. As Zeanah notes, the International Code Council's International Building Code (IBC) is designed to apply to any residential building that contains three or more dwelling units. The IBC is more complicated than the International Residential Code (IRC), which typically applies to single-family homes and duplexes, and requires specific construction features that increase costs. And most jurisdictions in the U.S. use some version of this code to regulate construction.
Zeanah tells the story of how he and his colleagues in Memphis and Shelby County, Tennessee, worked with a building code advisory board to adjust the local construction codes to allow three– to six-unit structures to build under the IRC. He notes that these changes were only possible because Tennessee allows local jurisdictions to adopt their own amendments to the standard codes. But based on Memphis and Shelby County's experience, planners may want to explore opportunities to make similar changes in their communities and, where those changes aren't possible, to focus their efforts on advocating for updates to the IBC and IRC.
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Top image: Sightline Institute / Flickr (CC BY 2.0)
About the Author
David Morley, AICP, is a research program and QA manager with APA and editor of Zoning Practice.