Missing Middle Housing consists of multi-unit housing types such as duplexes, fourplexes, bungalow courts, and mansion apartments that are not bigger than a large house, that are integrated throughout most walkable pre-1940s neighborhoods, often integrated into blocks with primarily single-family homes, and that provide diverse housing choices and generate enough density to support transit and locally-serving commercial amenities. Although many of these are a common feature in pre-war building stocks, these housing types have become much less common.
The term “missing middle” became popular in American and Canadian urban planning in the 2010s to describe a housing type that was many decades ago common in these countries but is now in many cases “missing”. Many forms of what is now described as “missing middle” housing was built before the 1940s including two-flats in Chicago, rowhomes in Brooklyn, Baltimore, Washington, D.C. and Philadelphia, two-family homes or “triple-decker” homes in Boston, and bungalow courts in California. Post-WW-II, housing in the United States trended significantly toward single-family with zoning making it difficult to build walkable medium density housing in many areas reducing supply of the now “missing” middle.
The resurgence of missing middle housing is due to many factors including resurgent demand for this type of housing, demand for housing in amenity rich walkable neighborhoods, the necessity of housing affordability, environmental efforts to support walk-ability and transit oriented developments, and changing demographic trends. The American Association for Retired Persons (ARRP) released new report, which showed that more and more, Americans want to “age in place,” and need easy access to services and amenities available in walkable, urban, transit-oriented communities. Millennials have been shown to drive less, and seek housing choices in walkable neighborhoods close to transit. The numbers of automobile miles traveled increased each year between 1946 and 2004; today Americans drive less than 2004, and no more per person than in 1996. The decline in driving is most striking among young people aged 16 to 34, who drove 23% fewer miles on average in 2009 than their age group did in 2001. “Millennials prefer amenity rich housing choices. These amenities are within walking distance,” presented Howard Ways of the Redevelopment Authority of Prince George's County in Washington D.C. “They prefer smaller units with open floor plans and are not interested in yard work at all.” Small Housing B.C. has stated that "The structure of the traditional North American suburb has failed to live up to the expectations of many who settled in suburban neighbourhoods, and new ways are being sought to re-engineer suburban living and re-build those settlement patterns."
Missing-middle housing comes in a variety of building types and densities but may be characterized by a scale similar to that of single family housing, location in a walkable neighborhood, and a smaller amount of parking. Forms of missing middle housing may include side-by-side duplexes, stacked duplexes, bungalow courts, accessory dwelling units (carriage houses, basement apartments, etc.), fourplexes, multiplexes, townhomes, courtyard apartments, and live/work units. These building types typically have a residential unit density in the range of 16 to 30 units per acre but are often perceived as being less dense because they are smaller in scale. Because of its scale, missing middle housing may mix into single family neighborhoods, act as an end-grain of a single family housing block, act as a transition between higher density housing and single family housing, or act as a transition from a mixed use area to a single-family area. The resulting density may support broader community desires, including walkable retail, amenities, public transportation, and increased “feet on the street”.
Missing middle is tends to become naturally affordable rental housing as it ages, and provides supports a level of density that supports the shops, restaurants, and transit that are associated with walkable neighborhoods. Missing middle housing units are usually smaller units than single family homes because they share a lot with other homes, which results in lower per-unit land costs. It is also one of the cheapest forms of housing to produce because it is typically low-rise, low parking, wood-frame construction, which avoids expensive concrete podiums. Since the construction and building materials are comparatively less complicated than larger mid-and high-rise structures, a larger pool of small-scale and local home builders can participate in the creation this form of housing. The efficient use of land and infrastructure may be financially productive for municipalities with more people paying taxes per acre for comparatively little infrastructure.
Missing Middle Housing offers greater choice in housing types that still blend into existing single family neighborhoods, unlike mid-rise apartment buildings. They are typically more affordable than a single-family home because they are smaller and share communal parking and lawns. Lloyd Alter of Treehugger says there is a certain amount of density required for building green cities that support transit-oriented development: "I have made the case that you don't want it too high; that there is a Goldilocks density that's just right. One form of housing that gets close to Goldilocks is the stacked townhouse."
Several states have adopted or proposed legislation aimed at increasing the stock of missing middle housing with Oregon notably adopting such legislation in 2019. Many municipalities are updating their land-use and zoning regulations to better support missing middle housing. Changes to land use regulations to support missing middle housing may also include changes such as form-based-codes, transit-oriented development, and other updates.
Portland, Oregon, has a number of historic Missing Middle housing types located throughout the city, most of which are duplexes, that were built before the 1920s before the city's first zoning plan was approved. Zoning for single-family homes was expanded in the 1950s and the building of duplexes or triplexes largely became illegal in Portland. Some local developers are now advocating for these Missing Middle types, saying that they are key to building the bike-friendly neighborhoods Portland is known for.
The Minneapolis, Minnesota Minneapolis 2040 plan calls for up-zones the city to allow two- and three-family buildings on what had been single-family lots, tripling the potential number of housing units in the city. Per the plan, the Minneapolis City council has adopted zoning updates to permit more missing middle housing. The new zoning in Minneapolis does not prohibit construction of single-family homes no neighborhoods in the city are zoned exclusively for single-family zoning. New duplexes and triplexes must be built within the existing building envelope, and up to two units can be added within that footprint to owner-occupied homes. Zoning changes also permit cluster development and accessory dwelling units while reducing parking requirements.
The City of Seattle proposed to remove regulatory barriers in their Land Use Code to make it easier for property owners to create accessory dwelling units (ADUs) and increase the number and variety of housing choices in Seattle’s primarily single-family zones. Seattle has adopted zoning changes to promote missing middle housing including permitting accessory dwelling units and expanding where missing middle housing types are permitted. Many other communities across the Pacififc northwest are working to support missing middle housing types including Eugene, Olympia, Spokane, and Bellingham, and Tigard among others.
Many communities of different sizes and locations are updating their land use regulations to support missing middle housing including smaller cities such as Bloomington, Indiana, and Canadian cities including Edmonton, Alberta among many others.