What Is a Family? Ask a Zoning Official.

Big cities like New York, Baltimore, and others use strict definitions of family to restrict housing.

The increased cost of housing is a major driver of inflation. It's even forcing modest change in the restrictive zoning codes that distort and restrict supply. California has now moved to legalize small "accessory dwelling units" on housing lots statewide and Minneapolis has rolled back single-family zoning.

Legal constraints on housing supply still abound, however. But less noticed than the exclusionary impact of 4-acre house lot requirements (as in Greenwich, Connecticut) is the fact that city officials are using thousands of local zoning codes to define what a family is. Doing so encourages inefficient use of the housing stock we have and stands in the way of living arrangements that could help young families and older Americans lower their housing costs.

Widespread local regulations limit so-called "unrelated" co-occupants (i.e., roommates or lodgers) even though there are no limits on the number of occupants related by "blood, marriage, or adoption" (the language often used by local zoning codes). Even when there are empty bedrooms that could accommodate more occupants, such rules stand in the way of older homeowners who might like to rent rooms to unrelated helpers, or younger families who would like to share quarters to more easily make their mortgage payments.

For a new American Enterprise Institute research paper, I reviewed zoning regulations in 30 major cities and nearby suburbs and found that, notwithstanding changing social norms, zoning restrictions on the composition of households remain common. Zoning codes in 23 of the 30 largest U.S. cities or nearby suburbs, impose limits on occupants deemed "unrelated."

In Village of Belle Terre v. Boraas (1974), the Supreme Court allowed localities to impose the "related by blood" regulations. The ruling upheld a New York village ordinance that "restricted land use to mean one or more persons related by blood, adoption or marriage, or not more than two unrelated persons."

Even traditionally tolerant cities have kept such restrictions. In New York City, for instance, as explained by the popular rental listing service, StreetEasy, Real Property Law stipulates that when two people sign a lease, "there should be no more than four occupants living in the apartment at one time."

Even stricter laws are not uncommon. In the city of Baltimore, no more than two unrelated persons may live together, unless in an approved rooming house. In Las Vegas, the limit is four; the same zoning limit applies in Grand Rapids, Michigan. No more than three unrelated persons may share a household in St. Louis; the same is true in Nashville, where housing affordability is a crisis.

Just because the Supreme Court found such laws to be constitutional does not, of course, mean that localities must adopt them. Change is not widespread but it is definitely afoot—including laws which distinguish between crowding (which may be a health and safety concern) and the relationships among residents.

Legislation in Oregon passed last year prohibited municipalities from regulating occupancy based on familial relations. Pam Marsh, a Democratic state legislator from Ashland, Oregon, said in support of the bill: "We know that unrelated people live together for lots of important reasons and there is simply no reason for cities to be regulating that." Property owners would not be barred from restricting occupancy based on potential crowding.

This has long been the legal rule in California, in the wake of a 1980 state Supreme Court decision which struck down a Santa Barbara local law that defined family as "two or more persons related by blood, marriage or legal adoption living together as a single housekeeping unit in a dwelling unit."

Change is not limited to blue states. In 2020, the Columbus, Ohio, suburb of Bexley revised its zoning code to recognize "persons living together as a functional family" who "share the entire dwelling unit and live and cook together as a single housekeeping unit." One can view this as cultural change—or simply a means to make better use of our existing housing stock.

This is no call for change dictated by courts or Washington, though. Gradual change at the local level is the best way to proceed. Some communities will prefer to continue to use their zoning law to endorse the traditional nuclear family with two parents and children. In the American federalist tradition, that should be their choice. Still, it's worth reexamining local laws that promote those preferences at the expense of the fuller and varied use of homes.

We've become accustomed to the idea that housing market pressures can only be relieved by grand policy interventions led by Washington. But the quiet zoning code definitions of what may constitute a family can both accommodate changing social norms—and help make sure bedrooms don't go empty while young families are locked out of communities in which they grew up. Let's consider leaving the definition of family to families themselves.