Where have all the new duplexes gone?
Updated: Sep 18
Ah the humble duplex. Two homes for the look of one. Twice the security & opportunity on a single lot. Nurturing American icons like:
Michelle Obama grew up on the top floor of a Chicago duplex owned by her aunt.
Bob Dylan lived the first six years of his life on the second floor of a Duluth duplex
Hewlett Packard was born in a garage behind a Palo Alto duplex that David Packard and his wife rented from a widow.
Duplexes make wonderful homes and neighbors. They blend seamlessly into existing neighborhoods, and support many different households, lifestyles, incomes. Yet in the last 60 years, nationally, the number of new 2-4 units home starts has dropped dramatically:
Housing Starts | April 1964 | April 2025 |
1,448,000 | 1,400,000 | |
901,000 | 953,000 | |
105,000 | 18,000 | |
442,000 | 429,000 |
In April 1964 and April 2025, the numbers for total, single family, and 5+ units housing starts were largely the same. But the numbers for 2-4 unit homes fell by 80%! The trend over the last 60 years is stark. During the 1960s and 1970s, the number of 2-4 family home starts varied (40,000-120,000 per year), but starting in the 1980s, 2-4 unit home starts plummeted sharply. They flatlined in the 1990s (~40,000 per year), fell again during the Great Recession and flatlined at a lower baseline (<20,000 per year) from 2010. (See all FRED housing data)
Why does this matter today?
2-4 family homes are physically similar to single-family residences (SFRs) and virtually indistinguishable. My block has 4 duplex and 2 quadplex buildings, yet my friends think I live in a single family neighborhood. During a recent block party, I met some wonderful people, a young architect, an engineer developing drones, a writer with college kids. Looking back over the years, we've had many lovely neighbors - young couples, post-docs, chefs, nurses, entrepreneurs.
Both SFRs and 2-4 family buildings are typically light, wood framed structures (Type V construction in building code speak), so they are the easiest and cheapest to construct. This is why 2-4 family buildings are especially relevant now. At 1-2 stories, they don’t have different structural, plumbing, mechanical requirements than SFRs. Contractors don’t need specialized labor and consultants. Utility hookups (electrical, water, sewer, storm) are about the same capacity and volume of a single family home. With SF Bay Area construction costs puncturing the $500/sf threshold, 2-4 family unit homes are the most cost effective and straightforward ways for cities to add diverse housing stock incrementally, especially near downtowns and commercial corridors.
Duplexes, triplexes and quadplexes provide more housing options for a wider range of households and incomes. They are naturally affordable housing options for people of all ages and situations:
Young professionals needing space to starting their careers
New families who want to live with community for convenience
Empty nesters with active lifestyles looking to downsize
Multiple generations looking to live with each other
Owning a duplex or triplex can provide residents with regular income to stay in their community
