Missing Middle Housing

Historic four-plex in Portland Oregon

The term “missing middle housing” was introduced by architect Daniel Parolek in 2010.[3][1][4][5] 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.[6] 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.[7][8]

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.[9][10] 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.[11] Millennials have been shown to drive less, and seek housing choices in walkable neighborhoods close to transit.[12] 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.[13] “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.”[14] 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 neighborhoods, and new ways are being sought to re-engineer suburban living and re-build those settlement patterns."[15]

Bungalow Court development where several small homes surround a central garden

Missing-middle housing comes in a variety of building types and densities but may be characterized by location in a walkable context, lower perceived density, small building footprints, smaller homes, reasonably low amounts of parking, simple construction, and focus on community.[16][17][18][19] 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.[20][21] 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.[22] 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.[23][24] The resulting density may support broader community desires, including walkable retail, amenities, public transportation, and increased “feet on the street”.[25]

Missing Middle Housing offers greater choice in housing types that still blend into existing single family neighborhoods. 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.[26] 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.[27][28] 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.[27][28] The efficient use of land and infrastructure may be financially productive for municipalities with more people paying taxes per acre for comparatively little infrastructure.[29]

Duplex like those permitted by state legislation in Oregon

Several American states have adopted or proposed legislation aimed at increasing the stock of missing middle housing. Most notably, Oregon adopted House Bill 2001 in 2019.[30][31] The Bill requires Oregon's medium-sized cities to allow duplexes on each lot or parcel zoned for residential use that allows for the development of single-family homes.[30] Additionally, Oregon's large cities (with population over 25,000) and cities in the Portland Metro region, must allow duplexes, triplexes, quadplexes, cottage clusters, and townhouses in residential areas.[30] The Bill set aside funds for planning assistance to local governments to help draft local codes and permits municipalities to set reasonable design and infrastructure standards.[30] The State of California has adopted a number of bills which promote accessory dwelling units (ADUs) and reduce regulatory barriers to ADU construction.[32][33] State level action has also occurred in Australia where, citing and effort to promote more ‘missing middle’ development, New South Wales launched a The Low Rise Housing Diversity Code and Design Guides for Low Rise Housing Diversity.[34][35]

Other states have introduced similar legislation to support missing middle housing types. The State of Illinois considered HB4869 which would have required municipalities to permit (and reasonably regulate) accessory dwelling units (ADUs).[36] Virginia considered HB 152 which would have required municipalities to allow (and reasonably regulate) missing middle housing types (duplexes, cottages, etc) on all lots currently zoned for single family housing.[37] The State of Maryland considered HB1406 "Planning for Modest Homes Act of 2020" which would have required census tracts that are affluent, transit-adjacent, and/or near a large number of jobs, to allow missing middle housing types.[38][39] Nebraska considered LB794 would mandate every city with more than 5,000 people to allow missing middle housing in areas previously zoned exclusively for single-family detached residential.[40][41]

Modern four-plex contains four units

Many municipalities are updating their land-use and zoning regulations to better support missing middle housing.[42][43] 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.[44]

In the United States, 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. In the 2010's Portland began updating their zoning regulations to permit Missing Middle Housing types.[45][46] Missing Middle zoning updates have spread through the Pacific Northwest and now include including Seattle[47][48][49] Eugene,[50][51] Olympia,[52] Spokane,[53][54] and Bellingham,[55] and Tigard[56] among others.[57]

Zoning Updates to support missing middle housing are not just found in the Pacific Northwest. Notably, In Minnesota, the Minneapolis 2040 plan called for up-zoning the city to allow more missing middle housing types throughout the city.[58][59][60][61][62] The new zoning in Minneapolis does not prohibit construction of single-family homes but no neighborhoods in the city are zoned exclusively for single-family zoning.[63] The City also eliminate mandatory parking minimums from its zoning regulations.[64][65]

Many communities throughout the United States are implementing at least some zoning reforms to support missing middle housing. Notable examples include Sacramento California which voted to permit up to four housing units on all residential lots and reduce parking requirements in order help the city alleviate its housing crisis and achieve equity goals.[66] Other examples across the United States include Bloomington Indiana,[67] Atlanta Georgia,[68][69] Grand Rapid Michigan[70] Austin Texas,[71] Durham, North Carolina,[72] Kirkland Washington's cottage housing zoning,[73] Madison Wisconsin's Low-Medium Residential zoning,[74] Montgomery County, Maryland's numerous housing studies.[75] While some communities have not adopted regulations to widely permit the full range of missing middle housing types, they have made changes to permit accessory dwelling units (ADUs). Diverse examples include large cities such as Los Angeles, CA[76] and the City of Chicago, IL,[77] and smaller cities such as Lexington, KY,[78] and Santa Cruz, CA[79]

Outside of the United States cities in both Australia and Canada have adopted missing middle housing reforms. Notable examples in Canada include Edmonton, Alberta's missing middle zoning reforms[80] and Vancouver British Columbia's secondary unit zoning.[81][82][83] In Australia, The 30-Year Plan for Greater Adelaide includes a focus on missing middle housing[84][85] and Moreland's Medium Density Housing Review.[86]

• Bicycle-friendly
• Form-based code
• New Urbanism
• Walkability