6.6 Density and Land Use

Residential density is the number of homes or people on a given area of land.

• Low-density areas offer more space and privacy but need more land, longer trips and more driving, and they cost more per household to serve with roads, pipes and buses.
• High-density areas support transit, walking and local shops and use land efficiently, but they can feel crowded and have higher housing prices per square foot.

History matters a lot. Cities that grew before cars, like Boston's older neighborhoods or most European city centers, were built compact so people could walk. U.S. cities that boomed after World War II, like Phoenix and Houston, spread out around highways. Bid-rent theory (6.5) also explains why buildings rise highest where land is most expensive.

Culture and economics matter too. In Hong Kong, steep mountains and limited flat land push housing upward. In Singapore, most residents live in high-rise public housing apartments built by the government. In the United States, many families value a detached house with a yard, and government mortgage policies after World War II favored that kind of home.

Zoning is local law that says what can be built where: housing, commercial or industrial, plus limits on building height, lot size and the number of homes per lot. The Supreme Court upheld zoning in Village of Euclid v. Ambler Realty (1926), and separating uses became the U.S. norm.

Large areas of many U.S. cities are zoned only for detached single-family houses, which keeps density low and limits new housing. Some places are changing this. Minneapolis's 2040 plan, adopted in 2018, allowed up to three homes on lots once limited to one, and Oregon passed a 2019 state law requiring many cities to allow duplexes on residential lots. Supporters say these changes add affordable housing; opponents worry about neighborhood character, traffic and strain on services.

Houston is the largest U.S. city without conventional zoning, though private deed restrictions control land use in many of its neighborhoods.

Infilling means building on vacant or underused land inside an existing city, like empty lots, old parking lots or abandoned factories. It adds housing and jobs without consuming farmland at the edge, and it uses existing roads and pipes. Redevelopment and adaptive reuse convert old buildings to new uses, like turning warehouses into lofts, which changes a neighborhood's land use and density. These changes can also raise property values and push up rents (6.10).