Triangular plots from old railroad lines. Crescent-shaped parcels that used to be parking lots. And narrow strips of land squeezed between buildings.
For decades, builders ignored irregular lots, typically smaller and narrower than standard square ones, because of zoning codes and rules. But as usable land becomes increasingly limited in urban areas, more cities and states are moving to change regulations to allow for building on odd plots, and for additional housing on land traditionally reserved for single-family homes.
Over the past year, the nation’s 250 largest cities have made 257 significant zoning changes to clear the path for denser development, according to an analysis provided by ReZone AI, a firm that analyzes municipal zoning.
State-level zoning changes have also accelerated, said Alex Horowitz, director of the housing policy initiative at the Pew Charitable Trusts. From 2023-24, 96 laws were passed to help increase housing production, including adding development in a given area, and 80 laws have been passed this year.
The zoning changes get rid of minimum lot sizes and parking requirements that housing advocates and developers say have made it nearly impossible to build “the missing middle,” or a variety of housing styles that fall between single-family homes and larger apartment buildings.
And nearly 20 cities and states are adopting the so-called single-stair reform, which requires fewer staircases in apartment buildings so they can be built on slender lots.
The old zoning rules left much of those lots underdeveloped. About 75% of the land in U.S. cities is earmarked for single-family homes, making it illegal to build multistory apartments on those properties.
“Land is really expensive,” said Arica Young, an associate director at the Lincoln Institute of Land Policy, a think tank focused on improving land-use policy. “If you build one home, there’s a limited market of people who can afford it. But if you put a triplex on that land, you bring down the cost enough where you can find buyers.”
Odd-shaped lots are typically less expensive, a selling point for builders at a time of elevated interest rates, tariffs on building materials, high insurance costs and a shortage of skilled construction workers.
Aside from the money issue, there just aren’t many unused square lots left. “Twenty years ago, in LA, New York or Chicago, developers went on the market and found a square lot,” said Ben Grunwald, an architect at J Frankl Architects in New York. “All the square lots are gone. Now you have to start looking at odd lots.”
Allowing developers to build small apartment buildings on irregular lots, or those zoned only for single-family homes, would help address America’s housing shortage, said Yonah Freemark, a researcher at the Urban Institute who recently wrote a paper on this topic.
Alli Quinlan, executive director of the Incremental Development Alliance, a nonprofit organization that has trained thousands of developers to build smaller homes, said she had seen significantly more affordable housing built since the changes.
In Seattle, the Corvidae Co-op was built on two adjoining single-family lots and has 10 units, from studios to two bedrooms, that were placed on the market last year. The development, which cost an estimated $3.2 million to build, was possible only because the city changed its rules to allow more density on residential lots, said Leah Martin, founder and partner of Allied8, the architecture firm that designed the project. The average sale price of the units was $380,000. (Seattle’s median home sale price in June was $930,000, according to Redfin.)
And there are hundreds of lots across the city where more housing developments like this can be built, Martin said. Her company is working with two others.
Smaller multifamily projects are popping up all over the country in places that have passed legislation making it more feasible to build on small and underutilized lots. From 2021-24, 1,400 permits for “missing middle” homes and dwelling units were filed in Portland, Oregon.
New California laws have provided opportunities for Mark Hogan’s San Francisco architecture firm, OpenScope Studio, to work on larger multifamily projects at formerly vacant parts of apartment complexes like parking lots, storage spaces and amenity buildings.
In New York, Peter Bafitis, an architect with RKTB, said the zoning reform that passed last year, called “City of Yes,” had encouraged more projects on odd-shaped, leftover lots. His firm has mocked up prototypes for apartments on properties as thin as 25 feet, he said.
“With small lots, development becomes more democratized,” Bafitis said, because it will give small contractors more opportunities to build midsize buildings.
In Minneapolis, a local builder, Rise Modular, took advantage of zoning changes to churn out a building a week over 16 weeks, delivering 84 affordable apartment units across the city in 2023. The homes were built in a factory, and the company worked with the city’s public housing authority, which owns hundreds of underutilized lots, to install them. The process was 33% faster and 20% cheaper than traditional building methods, Rise CEO Christian Lawrence said.
Although developers can now build in areas where they couldn’t before, they still face a number of challenges with bigger buildings on small and odd lots. Neighborhood groups and other residents are sometimes not happy about denser developments. And sometimes an irregular lot’s land conditions are too onerous. There can be curves and bends that developers have to maneuver around, or a massive rock taking up substantial space.
In the Brooklyn borough of New York City, 99 Fleet Place, an apartment building that opened to tenants in November, is called “the wavy building” by its design team because of its shape and narrow angled corridors. Because the lot is shaped like a bullhorn, the team had to shoehorn the elevators and mechanical systems toward the front of the space and bend the lobby around a courtyard, said Grunwald, who was an architect on the project.
Some cities are holding contests to help get as many starter homes built as quickly as possible. In May, Los Angeles announced 21 winners in its Small Lots, Big Impacts contest, which had more than 350 submissions. The city had invited designers, architects and students to propose housing concepts for “a selection of the city’s small, overlooked and forgotten lots.”
The winning designs will serve as templates for developers to build on small lots, some of which are the city’s roughly 4,000 underutilized parcels of less than a quarter acre, said Dana Cuff, a professor of architecture at UCLA, who helped organize the contest. The plan is to break ground on the winners’ concepts by next summer.
One of them, called Mini Tower Collective and designed by two New York firms, Ginzok Architecture and Studio BAD, proposed three wood-framed, four-story homes on a sloped site, creating a mini-hillside neighborhood with a shared side yard and panoramic views.
“We’re hoping these get built with the same qualities people love in single-family homes,” Cuff said. “The next generation of housing in LA can be more compact.”
New York City held a similar contest in 2019, but the winning designs were never adopted by developers. The city has lots as narrow as 13 feet, with areas as small as 1,008 square feet.
The new solutions are an encouraging sign, said Dan Parolek, the architect credited with coining the term “missing middle” and the founder of Opticos Design, which is based in Berkeley, California.
“The housing situation is so dire in every corner of the country, there needs to be solutions,” Parolek said. “There’s this ecosystem of small-scale builders and developers that’s really going to be the ones who go outside the box and step up and deliver these solutions.”