When it comes to foundation types used in single-family construction across the United States, slab foundations are king.
Some 73% of new single-family projects were built on slab foundations, according to a recent analysis by the National Association of Homebuilders. The Washington, D.C.-based trade group pulled its data from the 2024 U.S. Census Bureau's Survey of Construction, measuring a slim 0.6 percentage point increase from the 2023 slab usage. Still, the gap is widening between slab foundations and other understructures in new builds.
For its survey, the Census Bureau looked at three common foundation options for single-family structures: slab, full or partial basement, and crawl space. Known for affordability, slab foundations are often concrete poured flat on compressed dirt, offering ease and durability. They can, however, crack, minimize storage and complicate repairs for mechanical systems placed underneath them.
Basement foundations, used in 17% of 2024's new single-family homes, offer additional storage and shelter space, but they're pricier and prone to water infiltration, so they can be a risky choice in wet and/or warm climates. Arid climates can also have hardpan soil, making it time-consuming and challenging to excavate for a basement.
Crawl spaces foundations — deployed in a mere 9.2% of new homes last year — best suit homes in quake-prone areas because they elevate a house on blocks, stone or brick. They're not as expensive as basements, and they offer storage. But they can suffer from moisture and require extra insulation and pest maintenance.
Because of their different characteristics, foundation preference varies across the United States based on regional climates. Colder areas, including New England and other Northern states, favored basements, while the country's warmer regions — the rest of the East Coast, the South and the West Coast — relied heavily on slabs. No regions favored crawl spaces, the option that once reigned along the Pacific.
"The trend of increasing slab foundations is a mix of economics, climate suitability, construction efficiency and regional demand," Tyler Maddox, a regional sales manager at North America foundation repair company Groundworks, said via email. "Slab foundations offer both homebuilders and homebuyers substantial savings, speed and simplicity. Climate also plays a significant role, as warmer regions tend to have water problems if their homes are above a crawl space or a basement."
A national preference for concrete slab foundations doesn't show signs of reversing, Maddox noted.
"The upward trend shows no signs of slowing," Maddox said. "With ongoing cost pressure and evolving engineering solutions making slabs more broadly viable, this foundation type is positioned to remain dominant and expand into regions where they’ve historically been less common."