Missing middle housing

Missing middle housing refers to a lack of medium-density housing in the North American context. The term describes an urban planning phenomenon in Canada, the United States, Australia and more recent developments in industrialized and newly industrializing countries due to zoning regulations favoring social and/or racial separation over shared living arrangements, and the prevalence of cars allowing car-dependent suburban sprawl.

Medium-density housing is characterized by a range of multi-family or clustered housing types that are still compatible in scale and heights with single-family or transitional neighborhoods. Multi-family housing facilitates walkable neighborhoods and affordable housing, and provides a response to changing demographics.

Instead of focusing on the number of units in a structure, density can also be increased by building types such as duplexes, rowhouses, and courtyard apartments.

The term "missing middle housing" was introduced by architect Daniel Parolek in 2010.

Many forms of what is now described as "missing middle" housing were built before the 1940s, including two-flats in Chicago; rowhouses in Brooklyn, Baltimore, Washington, D.C., and Philadelphia; two-family homes or "triple-decker" homes in Boston, Worcester; and bungalow courts in California. Post-WWII, housing in the United States trended significantly toward single-family with zoning making it difficult to build walkable medium-density housing in many areas and, therefore, reducing the supply of the now "missing" middle.

At the end of the 19th and beginning of the 20th century, Canadian and American cities with few exceptions, most notably New York and Chicago which already had many tall buildings, were not dramatically different in form from their European counterparts. They had a relatively small physical footprint compared to their population size, and buildings were largely 3-7 stories tall surrounded by a relatively modest ring of streetcar suburbs. Most city dwellers who were in the lower to middle-income brackets lived in dense urban environments within a practical distance of their workplace.

The less well-off typically lived on either the upper floors of multi-unit residential buildings, as most did not have elevators, or in tenements. Merchants frequently lived in a residential unit above their store. Those who were better-off may have lived in a rowhouse or terrace, and starting toward the end of the 19th century, perhaps in a streetcar suburb still relatively close to the city centre. Overall, the typical arrangement of urban spaces was one where communities were serviced by small-scale owner-operated shops and transport to non-walkable destinations was done by bicycle, bus, streetcar, or train.

Traditionally those in the highest income brackets had typically lived in large houses outside of, but often near to, the city. They travelled to the city originally by horse carriage and later by automobile. For most people, the need to live close to their job significantly limited spatial social stratification beyond economic class. This situation collapsed in the wake of explosive expansion of post-war suburban sprawl, which enabled white flight.