Missing middle housing

[3] 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.

[8][9] 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.

[10] Most city dwellers who were in the lower to middle-income brackets lived in dense urban environments within a practical distance of their workplace.

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.

[10] 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.

[11] The early to mid-twentieth century implementation of the suburb was thoroughly informed by this social context, and it was not uncommon for policymakers to inappropriately conflate small residential unit size, insanity, and crime with the traditional urban form; while simultaneously idealizing “rural” and upper class style estate living as its cure-all.

[13] Pro-automobile interests advocated for the removal of non-drivers from the road, and particularly targeted pedestrians with the invention and criminalization of “jaywalking.”[14][15][16] Importantly Federal, State, and Provincial governments undertook massive highway building programmes and also directly subsidized the purchasing of new suburban homes (Levittown being the prototype).

The resulting policies radically reformed cities into ones that typically have a unicentric urban core which is dominated by tall buildings built to be reliant on office uses with the area often referred to as the central business district (CBD).

This new "urban core" of stacked office uses is typically surrounded by swathes of sub-urban and peri-urban landscapes dominated by single-family homes with gardens serviced by the private automobile, car-centric retail destinations, and vast highway networks.

[22] The loss of flexible middle-density development serviced by affordable and widely used public transportation has resulted in high commute times for commuters, which have remained stubbornly unaffected by further investment in new road capacity due to the nature of induced demand, a practical limit on the space required to move large volumes of people in relatively large vehicles, and greatly increased costs for both the vehicle owner and government due to the inherent inefficiency compared to previous modes of transport.

[citation needed] Car-centric cities are less climate-friendly due to impacts relating to inefficient use of resources, volume of paved area contributing to flood risk, and potential loss of natural habitats to human development.

[citation needed] Without middle-density development to support them, cities have lost retailers not operating with substantial economies of scale.

[citation needed] These places are important for recreation, meeting neighbours, for adults to make friends, and for community organization.

The loss of these third places and small businesses is due to the need of both to rely on proximity to a large number of people for whom visiting them is easy, can be spontaneous, and would not require a special trip.

[citation needed] Some have suggested the loss of genuine “third spaces” as a contributing factor to a perceived reduction in a sense of belonging, inter-group social cohesion, and a rise in generalized loneliness.

[27] The polarization of Canadian and American cities into ones dominated by low- and high-density development with little in-between, has been due to implementing strict single-use land-use zoning laws at a municipal level which prioritizes these use types while making new medium-density illegal.

[67] These critics say that the problem is with trying to zone for what planners think a city looks like; rather than creating the transport and legal conditions to allow it to take shape organically.

These controls are intended to allow adequate light and ventilation between buildings and on roads, and to ensure a decent quality of housing.

[71][72] This approach to not require car parking provision or private yards/gardens in areas with high degrees of good connectivity is seen as desirable because: access to common outdoor green space is seen as sufficient for these needs or, at the very least, an acceptable tradeoff for the convenience of improved connectivity; the provision of sprawling lower-value land-uses like private car parking and residential garden spaces in such locations is viewed as a poor return on investment by developers eager to maximize living space and plot utilization; urban planners who are eager to avoid the imprudent use of limited public funds with respect to the large nominal and operational costs of public transportation, water, power, roads, etc.

This approach to zoning gives the landowner more flexibility in using the land while still precluding harmful or inappropriate development and maintaining the benefit of remaining predictable and easy to understand.

Form-Based Codes foster predictable built results and a high-quality public realm by using physical form (rather than separation of uses) as the organizing principle, with less focus on land use, through municipal regulations.

[81][82] The resulting density may support broader community desires, including walkable retail, amenities, public transportation, and increased "feet on the street".

[93] In Massachusetts, H.5250 was adopted to require municipalities near the MTBA to reasonably allow duplex or multi-family housing near transit stations.

[97][98][99] In 2019, Washington State adopted E2SHB 1923 encouraging all cities under the Growth Management Act (GMA) to increase residential capacity by supporting many forms of missing middle housing.

[102][101][103] In 2022 Maine adopted bills LD2003 and LD201 that implement several affordable housing strategies including allowing accessory dwelling units and duplexes on residential lots statewide and permitting fourplexes in certain "growth areas".

[120] Virginia considered HB 152 which would have required municipalities to allow, and reasonably regulate, missing middle housing types (duplexes, cottages, etc.)

[121] 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.

[122][123] 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.

[198][199][200] Montréal, Québec is notable for its distinct architecture and urban planning that has historically included significant amounts of missing middle housing.

[201][202] Due to its unique history, many neighborhoods in Montreal include low-rise attached duplexes, triplexes, and apartments often with exterior stair-entry, minimal front setbacks, and with small backyards.