Here's how the size of homes built in the Bay Area has changed over the past 120 years

San Francisco Chronicle​

23-04-2025

For decades, newly constructed homes in California were getting bigger and bigger.
Not anymore. Statewide, homes built in the 2020s are about 2,150 square feet, down slightly from a peak of 2,340 in the 2000s, according to data provided by real estate company Zillow.
The tide against increasingly bigger homes turned sooner in some places than others, including in much of the Bay Area, where construction has slowed in recent decades.
The median square footage of a San Francisco home built in the 2020s is about 1,510. That's a steep drop from the city's median of 2,050 square feet in the 2010s. And it's much smaller than homes in San Jose, where newly built homes have continued to grow to a new record median of 2,560 square feet.
Zillow's estimates, based on the homes for which the company has square footage and year-built data, are of finished square footage, which don't include garages or unfinished basements. The data is also based on the homes' square footage as of April 2025, meaning older homes that have been remodeled and expanded will have their newer square footage reflected in the medians.
Newly built Bay Area homes larger than about 2,000 square feet became much more common starting in the 1980s, Zillow's data indicates, especially in Silicon Valley, Marin County and East Bay suburbs. Homes built around the turn of the millennium were often some of the largest, a trend mirrored in the rest of California.
Even in cities where homes were already relatively large, properties expanded even more. The median size of a home built in Atherton, an ultra-wealthy suburb in Silicon Valley, was 'just' 3,100 square feet in the 1950s — one of the largest of any California ZIP code in Zillow's data with at least 50 homes built that decade. Now, that median has more than doubled, exceeding 7,000 square feet.
The historically growing size of homes, and the shrinking seen in recent years, is a trend seen across the U.S. But it's not one that has a ready explanation, especially since some cities — including San Jose — are still seeing homes get bigger.
One factor is the former popularity of ' McMansions.' The large, amenity-rich homes accommodated the desire of homeowners for more space at a time when the country's homeownership rate was reaching record peaks. But after the Great Recession hit, builders made homes somewhat smaller for a time. Demand for more affordable 'starter homes' has also pushed the size of new construction down in some areas, while interest in larger spaces during the pandemic had the opposite effect in others.
Other, more specific factors are also likely at play in the Bay Area, though it's difficult to parse out what's exactly going on without more detailed data, said Issi Romem, a fellow at the UC Berkeley Terner Center for Housing Innovation. He speculated that San Francisco is seeing smaller homes this decade because the city is building more multifamily units, especially condos, which tend to be smaller than single-family homes.
That's also occurring in San Jose and Oakland, Romem added, but those cities may also be seeing a countervailing force, as larger home-building projects replace older buildings with newer, larger structures, a practice that is less common in San Francisco where lot space is more limited.