Zoned out: learning from Tennessee’s invisible affordability barrier
California may have okayed ADUs; and duplexes are technically legal in Cupertino, Palo Alto, and beyond—but only in narrow zoning pockets, leaving most of the map frozen in single-family exclusivity. Tennessee’s zoning atlas model could expose the gap and push Bay Area suburbs toward gentle density. From Beacon Center of Tennessee.
In 2020, Tennessee became the top U.S. magnet for in-migration, and housing can’t keep pace. Nashville homes now sell within ten days and Metro estimates it needs nearly 54,000 new units by 2030.
Zoning is the biggest invisible barrier: Nashville allows apartments on just 11% of its zoned land. Duplexes are banned on 59% of land across Middle Tennessee; multifamily housing is off-limits on almost 94%.
ADUs could help but they’re often neutered. While ADUs are technically allowed on nearly 58% of land, only 34% may rent to non-family; most jurisdictions restrict them to family-use only.
Driving restrictive land use means longer commutes, lost productivity, and even reduced wages. Studies estimate zoning missteps cut a staggering $1.6 trillion from Americans’ collective income annually. In crippled towns, lifting just three cities' codes could lift real per-capita income 8%.
The Tennessee Zoning Atlas uses standardized methodology created by the National Zoning Atlas to study, analyze, and calculate how local governments in Davidson, Williamson, Maury, Rutherford, Wilson, and Sumner counties treat different types of housing. We chose to first focus on these communities in Middle Tennessee because they are among the fastest-growing counties in the state, let alone the country, all with populations over 100,000.
The Tennessee Zoning Atlas shows how local government zoning policies make housing unaffordable and worsen Middle Tennessee’s housing shortage, often at the expense of low- and middle-income families. The Tennessee Zoning Atlas highlights the need to reform strict local government zoning regulations with pro-housing reforms that make it easier for property owners and builders to respond to the growing needs of our community. Some key findings include:
In Middle Tennessee, most of the land is for non-residential purposes or solely single-family housing as more affordable options like two-family housing (duplexes) are banned on nearly 59 percent of land and 3+ family housing (multi-family) is banned on nearly 94 percent of land.
Of the jurisdictions studied, land zoned by Maury County allowed “affordable housing” (at least two-family housing) the most, with nearly 96 percent of land eligible for affordable style housing, with Forest Hills and Sumner County as the lowest, not allowing two-or-more family housing anywhere.
Other forms of housing that could be options for low-income individuals or families, like ADUs, are often outright banned. Of the cities studied, Mt. Pleasant welcomed ADUs the most, with ADUs allowed on 100 percent of land, and Westmoreland the least, where ADUs are completely prohibited.
However, ADUs are often limited to family members and cannot be rented by the public. In fact, while nearly 58 percent of land in Middle Tennessee may allow an ADU, an ADU can only be rented to non-family members in 34 percent of Middle Tennessee.
Societal Costs
These zoning restrictions not only impact individual families looking for affordable places to live but inflict massive costs on society. Studies show how restrictive zoning requirements have forced cities to continue developing further into the countryside—creating longer commutes, increased traffic, lowered productivity, and job relocations not based on opportunities, but on housing costs. One study found that after adjusting for inflation, downstream consequences of zoning have robbed Americans of about $1.6 trillion in estimated wages per year.7 If only three cities reformed their zoning codes, the average American’s income would rise eight percent—a nice pay raise in a time of high inflation.8 By reforming these restrictive zoning regulations, we can increase the prosperity of everyday Tennesseans.
[Editor's note: California legalized accessory dwelling units under SB 234 and AB 68, and SB 9 eased the path for duplexes. However, cities like Cupertino and Palo Alto limit it to narrow pockets of their cities. A zoning transparency tool like Tennessee’s atlas could expose just how little land is available for multifamily housing in Silicon Valley. Pairing that with reforms like SB 450 duplex-by-right overlays on transit corridors might help unlock housing where it’s most needed.]
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