NAHB analysis of the Survey of Construction (SOC) shows that 58.9%t of all new single-family started in 2017 were built on slab foundations, followed by 26.1% with a full/partial basement, and 13.9% with a crawl space. The most common foundation types differ by region and largely depend on the local geography and climate conditions.
The foundation types for residential construction are closely related to climate conditions, especially the frost line. Homes in colder areas, where building codes normally require foundations built below the frost depth, are predominately constructed with full or partial basements. The division with the highest share of full/partial basements in new homes is the New England (82.1%), followed by the West North Central (77.8%), and the Middle Atlantic (66.4%). In these divisions, full/partial basement foundations offer additional finished floor areas at a marginal increase of construction cost.
Slab foundation homes are more common in warmer divisions, including the West South Central (97.6%), the South Atlantic (72.7%), and the Pacific (65.9%). The increasing adoption of slab foundations in these divisions is largely due to the lower material and construction cost compared to other types of foundations. Moreover, slab foundation needs the least amount of maintenance in the long run.
Foundations in the East South Central division included 47% crawl space with an increasing trend and 34% slabs with a decreasing trend. Since 2003, the share of new homes built on crawl space foundations increased from the lowest level of 17.6% in 2004 to the highest of 47% in 2017. On the contrary, the share of homes built on slab foundation declined from the highest of 61.0% in 2004 to the lowest of 34.1% in 2017.