NAHB analysis of the latest Survey of Construction (SOC) shows the gap between slab and full/partial basement foundation adoption rates is growing: The share of new homes built on slabs steadily increased from 46% in 2000 to 65% in 2020, while the share of new homes with basements dropped from 36.8% to 22%.
There are large regional differences in foundation types across the nation. Homes in colder areas, where building codes normally require foundations to be built below the frost line, are predominately constructed with full or partial basements.
The division with the highest share of full/partial basements in new homes is New England (79.8%), followed by the West North Central division (77.2 %), the Middle Atlantic division (69.5%) and the East North Central division (54.3%).
New homes with slab foundations are most common in the West South Central (95.7%), South Atlantic (79.4%), Pacific (67.7%) and Mountain (48.1%) divisions. They are most popular in the West South Central division, where new single-family homes have been primarily constructed on slab foundations over the past 10 years.
A warmer climate makes building on slab more cost effective, compared to full/partial basements. Slab foundations also need the least amount of maintenance in the long run. In the East South Central division, 43% of new homes started in 2020 had a crawl space and 38% were built on slabs.
NAHB Senior Economist Na Zhao provides more analysis in this Eye on Housing post.