March 21, 2022
One-third of American households are made up of a single individual. Up to 85 percent of households will not include children by 2025. By 2030, one in five Americans will be over the age of 65.
These statistics add up to a simple fact: Demand is high for smaller homes, lower living costs, walkable neighborhoods, and places for people to age in place. Yet zoning across the U.S. largely discourages these features.
That's because codes tend to be based on residential density, which is measured in dwelling units per acre, and most prioritize single-family housing. In 2019, The New York Times found that "it is illegal on 75 percent of the residential land in many American cities to build anything other than a detached single-family home." Not only are large multifamily buildings banned from many neighborhoods, but so are smaller housing types that cost less than a single-family home: side-by-side and stacked duplexes, triplexes, townhouses. These constitute "missing middle housing," or "house-scale buildings that just happen to have multiple units in them," says Daniel Parolek, principal and CEO of Opticos Design, who coined the term in 2010.
In the past few years, Oregon, Minneapolis, California, and other states and cities have launched zoning reform efforts to better promote housing affordability, diversity, and density. But if your community lacks the political will to make these kinds of sweeping changes, a few thoughtful tweaks can still make a big impact. Try these five zoning hacks — and a bonus tip — recommended by Parolek, then watch his APA Learn course for more ways to increase local density.
1. Reduce minimum lot size.
Does your code require two lots to build a duplex or a fourplex? If a builder must aggregate multiple lots to build a small multiunit building, your minimum lot sizes are too big. Instead, replace minimum lot sizes with minimum lot widths and tie types of buildings to the lot's width, not its square footage.
2. Allow for more housing types and revisit structure sizes.
As Joe Zehnder, chief planner for Portland, Oregon's Bureau of Planning and Sustainability, says, "if the house size is the same, why do you care how many units are in there?" In Portland, zoning changes now allow someone building on a 5,000-square-foot lot to construct up to four units divided between a main building and detached accessory dwelling units. Five or six units are allowed if half of them are affordable to low-income residents.
3. Level the playing field for smaller units.
More density doesn't always mean bigger buildings. In Santa Barbara, California, an average unit size ordinance provides for increased density as the average unit size decreases. This enables missing middle housing by allowing for greater density, even in smaller structures.
4. Reduce or eliminate parking minimums.
Parking expert Professor Donald Shoup, FAICP, of UCLA estimates that the U.S. has set aside two billion parking spaces for just 250 million cars and light trucks, resulting in far more land dedicated to cars than housing.
"If you want missing middle [housing], you need to fix your parking standards," says Parolek. "We've done a better job delivering houses for cars than we have delivering houses for people." If you require more than one off-street parking space per unit, it's not economically viable or physically possible to create missing middle housing on infill lots. Instead, opt for one parking space — or even none — per unit and no guest parking.
In suburban or rural areas, like Beaufort County, South Carolina, driving might be a fact of life. Try being creative about how you design parking so it can become an extra unit in the future, if factors like demand or public transit change.
5. Allow missing middle housing everywhere (if possible).
Is more than 20 percent of your land area zoned exclusively for single-family housing? Then you need to change the boundaries limiting missing middle housing to deliver it effectively and equitably. In Portland, Oregon, planners proposed allowing middle housing types in all districts across the city unless there is a physical limitation, like flooding or landslide hazards.
In response to displacement concerns, Zehnder says, "the more places where we allow this to happen, the less it's going to overwhelm any individual place." And development won't happen all at once: Portland planners estimate an add of 4,000 new units over the next 15 years. But if a single house in a wealthy neighborhood is replaced with three units, that alone can help take the pressure off demolitions in an area with lower incomes, Zehnder says.
Frame the conversation. When you're presenting your ideas to the community, especially those resistant to change, it can be helpful to avoid terms that might have negative connotations to some, like "density," "multifamily," or "upzoning." Present zoning changes as a way to offer new housing choices or options. Focus on form and scale, not density metrics. Imagery can help community members understand how missing middle types could look in their neighborhoods, too — check out missingmiddlehousing.com for resources.