2025 was the strongest year for “missing middle” construction since 2007. But the numbers tell a different story.
Just 19,000 units were built nationwide. That’s up slightly—but still only 5% of total multifamily construction. For a housing type that everyone agrees we need, that’s barely movement.
This isn’t a demand problem. It’s a production problem.
For most builders, duplexes, triplexes, and fourplexes—the kind of “missing middle” housing meant to sit between single-family homes and large apartment buildings—don’t pencil.
Zoning limits density. Financing favors larger projects. And the result is predictable: builders follow the economics, not the headlines.
Portland offers a glimpse of what happens when those incentives change.
Portland determined that the key factor was square footage. Specifically, a measure known as “floor-area ratio.”
In most of the city, the updated regulations limit the size of a single-family house to half the square footage of its lot—so on a typical 5,000-square-foot lot, the house can be a maximum of 2,500 square feet.
But if developers build something with multiple housing units, they are allowed to go bigger. On that same lot, a duplex could be 3,000 square feet, or a triplex could be 3,500 square feet, or a four-plex could be 4,000 square feet. And developers can count on making more money from those multiple units collectively than from a single-family home.
It seems to have worked: In the first year after the rules went into effect in 2021, 88 percent of new building permits were for middle housing and accessory dwelling units, far outpacing single-family homes. And fourplexes were three times as popular as duplexes and triplexes. The city said last year that it had permitted 1,400 of the denser homes in three years.
That’s the real lesson.
“Light-touch density” policies—allowing more homes per lot—can work. But only when they align with how projects are financed, designed, and sold.
Until then, the missing middle will stay missing. Not because builders won’t build it. Because the system still won’t support it.
