When Missing Middle Isn't Enough, Look to "Stickplexes"

This article first appeared on the Market Urbanism website. It is republished here with permission.

---

A “stickplex” is a dense residential structure or group of structures built with inexpensive materials and techniques, most commonly wood. Stickplexes use 2,500 square feet of land per unit or less. Stickplexes have per-square-foot construction costs roughly in line with detached houses due to avoidance of costly features like elevators and more expensive construction methods.

This type of housing includes features of both multifamily housing and single-family housing. They economize on land while avoiding the high construction costs of large multifamily buildings. Relative to high-rise housing, stickplexes can cost one-third less to build on a per-square-foot basis. And because they use a relatively small amount of land per unit, their land costs are lower than the typical detached house’s land costs.

Stickplexes versus missing middle

Daniel Parolek coined the term “missing middle” and emphasizes that missing middle “is compatible in scale with single-family homes.” He advises caution about permitting three-story buildings, while a stickplex can be three stories or taller. A duplex on a 6,000 square foot lot would fit the definition of missing middle. But it would not be a stickplex since it would use more than 3,000 square feet of land per unit.

Missing middle housing has found traction politically. Policymakers who have passed zoning reform from Oregon to Nebraska to Durham have used the term to describe the type of construction they would like to see. Minneapolis Council Member Lisa Goodman described the city’s reform to permit triplexes in language similar to Parolek’s:

“I like to refer to it as, ‘the box can’t change,” she said. “All that can change is how many families can live within the existing box.”

However, in Minneapolis, questions remain about how feasible triplexes will be to build in permitted building envelopes. Zoning rules, including floor area ratio limits of less than one and height limits of 2.5 stories for the two largest residential zones, may mean that triplexes aren’t as in-demand as they would otherwise be. These rules may be responsible for the low number of triplexes that have been permitted in Minneapolis under the first several months following the reform. In many cases, the single-family houses at their current size can’t comfortably accommodate additional, well laid out units.

Prior to Minneapolis’ triplex reform, its restrictions on the size of single-family houses were intended to prevent single-family houses from being replaced with “McMansions.” Many localities have similar polices intended to prevent change when housing costs rise but denser redevelopment is banned. Should these localities reform single-family zoning, anti-McMansion rules will stand in the way of infill development.

Sometimes missing middle isn’t enough

Part of the appeal of reforms like Minneapolis’ to permit missing middle housing is the promise of neighborhoods accommodating new residents without changing physical structures. But infill construction that adds housing supply at scale often adds square footage in addition to new units. For example, stickplexes are sprouting in my neighborhood in Washington, DC, pictured above and below. They have increased both the number of units per lot and square footage substantially.

There are some counterexamples. Property owners chop up brownstones in pricey neighborhoods, for example, allowing large houses to accommodate more units in an existing envelope over time. But these large, vertically-oriented units are particularly well-suited for this transformation. Additionally, neighborhoods of attached housing or small-lot housing, particularly ones that include lots of subdivided houses, can offer all of the benefits of urban living. This arrangement includes enough population density to facilitate walkable, amenity-rich neighborhoods and viable public transit. Subdividing standard, detached suburban houses on large lots (whether they’re inside or outside central city jurisdictions) into multiple units will not, in many cases, offer these benefits, but will come with the downsides of sharing walls.

To facilitate missing middle housing, Parolek proposes several different, very specific sets of zoning rules. He provides model zoning language to permit duplexes, cottage courts, and multiplexes, to the exclusion of other typologies. He argues that larger multifamily projects should be banned where missing middle is permitted. Otherwise, he says, land would be too expensive for missing middle to be feasible. As Salim Furth shows this restriction points to the limits of missing middle’s affordability advantages.

Parolek emphasizes aesthetics. He disowns many examples of actually-existing infill development because they are either out of context with their neighborhoods or because they don’t meet his standards for walkability. Some of my favorite examples of infill construction—from Los Angeles dingbats to New Jersey duplexes—are out because they include tuck-under parking. I agree that these forms of stickplexes aren’t ideal urbanism. But stickplexes are defined by their feasibility and cost advantages relative to single-family development, rather than by their individual contributions to walkability.

Zoning for stickplexes

Zoning to permit stickplexes is simpler than zoning for missing middle. Stickplexes don’t require zoning designations that encourage a specific housing format. They simply require that a locality zone for so much multifamily that the highest and best use of some land zoned for multifamily is dense, walk-up stick construction. That is, zoning that isn’t binding at every location.

On the other hand, reforming single-family zoning to permit feasible stickplexes often requires reforming more than just repealing single-family zoning. In Houston, where tens of thousands of infill townhouses have been built, the floor area ratio of townhouses is generally well over one. Most single-family zoning districts in the U.S. wouldn’t allow this level of density even if they were to eliminate single-family zoning. Stickplexes thrive with height limits of 40-feet or higher, low or no lot-size requirements, no unit restrictions, and small setback requirements.

Zoning for missing middle housing has political advantages in terms of promising neighbors that any redevelopment will have a specific aesthetic. But zoning for a specific aesthetic may mean that nothing is feasible to build in neighborhoods that need new housing. Zoning for stickplexes ensures that as housing costs rise, homebuilders are able to respond with new housing.

---

---

About the Author

Emily Hamilton graduated with a Masters in economics from George Mason University in 2010 after finishing her undergraduate degree at Goucher College. While at GMU, she worked as a Research Associate at the university’s Mercatus Center. After a brief time working elsewhere, she returned to the Mercatus Center to write for Neighborhood Effects about state and local policy issues.

Emily was first introduced to Jane Jacobs while working as an intern in the Planning Department of my hometown in Colorado. Jacobs’ work enlightened Emily to the power of market forces to benefit all city dwellers without government intervention. Since then, Emily has become fascinated by the urban emergent order that creates our cities. You can contact Emily at emilybwashington@gmail.com