What’s the best way to enable Missing Middle Housing?

Hint: Conventional Zoning Doesn’t Work

Conventional (Euclidean) zoning practice regulates primarily by land use or allowed activities, dividing neighborhoods into single-family residential, multifamily residential, commercial, office, etc. This separation of uses is the antithesis of mixed-use walkable neighborhoods. Along with use, the zones are often defined and controlled by unpredictable numeric values, such as floor area ratio (FAR) and density, which create all sorts of barriers to Missing Middle Housing.

For starters, Missing Middle Housing (MMH) is intended to be part of low-rise residential neighborhoods, which are typically zoned as “single-family residential” in conventional zoning. However, because MMH contains multiple units, it is, by definition, not allowed in single-family zones. On the other hand, most multifamily zones in conventional codes allow much bigger buildings (taller and wider) and also typically encourage lot aggregation and large suburban garden apartment buildings. The environments created by these zones are not what Missing Middle Housing is intended for.

In addition, density-based zoning doesn’t work with the blended densities that are typical in neighborhoods where Missing Middle Housing thrives. MMH are similar in form and scale to detached single-family homes, but because they include more units, they often vary dramatically in their densities, making them impossible to regulate with a density-based system. For example, a bungalow court can have densities of up to 35 dwelling units per acre even though the buildings are only one story tall, because the size of each cottage is only 25 feet by 30 feet. So if a zoning district sets a maximum density of 20 dwelling units per acre, it would not allow the bungalow court type. On the other hand, if the zoning district has a maximum density of 35 dwelling units per acre with few or no additional form standards, every builder/developer will max out a lot with a large, out-of-scale apartment building, rather than building the bungalow court the neighborhood would prefer.

And one more thing: density-based zoning treats all units the same regardless of size. This means that a 3,500-square-foot unit is considered the same as a 600-square-foot unit for calculations such as density, parking and open space, thus discouraging much-needed smaller units. For example, a fourplex with four 600sf units would require four times the parking and open space as a 2,400sf detached single-family home, even though the size of the building is the same, typically making the fourplex infeasible to fit on a typical lot.

This Alameda, CA neighborhood has several Missing Middle housing types on each block.

The Alternative: Form-Based Coding

Form-Based Coding is a proven alternative to conventional zoning that effectively regulates Missing Middle Housing. Form-Based Codes (FBCs) remove barriers and incentivize Missing Middle Housing in appropriate locations in a community.

FBCs represent a paradigm shift in the way that we regulate the built environment, using physical form rather than a separation of uses as the organizing principal, to create predictable, built results and a high-quality public realm.

The Form-Based Approach to Regulating Missing Middle Housing

Regulating Missing Middle Housing starts by defining a range of housing types appropriate for the community based on the community’s existing physical patterns, climate, and other considerations, as part of the early Community Character Analysis phase of a planning and Form-Based Coding project.

A building types page from Cincinnati’s Form-Based Code

Then for each form-based zone, a specific range of housing types is allowed based on the intention for the neighborhood. For example, in a walkable neighborhood, single-family-detached homes, bungalow courts, and side-by-side duplexes may be allowed, or in a slightly more urban walkable neighborhood, bungalow courts, side-by-side duplexes, stacked duplexes, fourplexes, and small multiplexes might be allowed.

A zone from the Cincinnati’s Form-Based Code

In addition for each type, there are typically supplemental form standards that are regulated to allow some of the individual aspects of certain MMH types while preventing overbuilding in terms of height and bulk. For example, a bungalow court type typically allows for more units, but has a maximum height of 1–1.5 stories, a maximum building footprint/unit size of around 800 square feet and a minimum size of courtyard. A Form-Based Code can regulate these fine-grained details, such that on a 100′ by 100′ lot, two fourplexes or a bungalow court with eight small, one-story units could be allowed, but not a single, larger eight-unit apartment building.

For these reasons and more, Form-Based Coding is the most effective way to enable Missing Middle Housing.

The small multiplex building type from Cincinnati’s Form-Based Code

“I want to thank you for your great work on Missing Middle Housing! It has been useful in my current research on policy reforms to support more affordable infill development in Victoria, B.C., and informing my report ‘Affordable Accessible Housing in a Dynamic City.’”

— Todd Litman, Victoria Transport Policy Institute

For more information about Form-Based Codes, see:

Form-Based Codes with Building Types to Reference:

Or find out about our Form-Based Coding services

Illustration of the variety of places regulated by Flagstaff’s Form-Based Code

Learn more about Missing Middle Housing