Single-Story and Slab Foundations Dominate New Builds

Three-quarters of single-family homes are produced with intent to sell, with the remainder built by owners or as designated rental properties.

By Manuel Gutierrez, Consulting Economist to NKBA

Single-family houses can be compared to each other using a variety of metrics, from aspects of construction to aesthetics and location. This report focuses on construction and building styles.

One key characteristic that differentiates single-family homes is the number of stories. The split is very close between one and two-story homes, although historically two-story houses have predominated. Despite this long historical trend, for the first time last year, single-story homes overtook two-story dwellings as the most popular. A potential reason is that as baby boomers reach retirement age and downsize, they often move to single-story living, whether in the general community or in 55+ developments. Kitchen and bath designers should pay close attention, because this is a boost for universal/aging in place design.

The upper-right panel of Figure 1 shows that 448,000 one-story homes were completed in 2020, 47,000 more than the 401,000 two-story houses. Only 5% of single-family homes had three or more stories.

Another construction metric is a home’s foundation. Some have full or partial basements, others a crawl space, and still others are built on a slab. The most popular is a slab foundation — nearly two-thirds (64%) of the new single-family houses completed last year were built on a slab, for a total of 576,000 single-family houses (Figure 1).

Two-story homes are less likely to be built on a slab, just 55% compared with 70% of all single-family homes.

Among two-story homes, 50% more, or 27%, have a basement compared with only 18% for single-story homes.

More than 22% of homes had either a partial or full basement, representing 202,000 houses. The least popular foundation type is a crawl space, with just 11,000 such houses built last year.

Another construction feature is whether the houses are built on-site or are modular or panelized. The data reveals that the vast majority — 96% last year — of single-family homes were built on site.

Finally, a fourth consideration is a builder’s intent for the house. Three-quarters of the single-family houses are built with the purpose of selling them, and just 6% are constructed with the intent of renting them. The remaining 19% are built by owners themselves, either by hiring a contractor or by acting as his/her own contractor. The number built strictly for sales purposes is somewhat higher for two-story homes, at 80%.

Regionally, there are vast differences in preferred construction types, illustrated in Figure 2.

Houses with a slab foundation are much more common in the Southeast as well as the in the Pacific Southwest. Land availability and flood-risks are likely determining factors for choosing this type of foundation.

Single-story homes are more prevalent in the South. While nationally half of the single-family houses are one story, that figure rises to 60% in the Southern states. Again, this could reflect the desire of many older Americans to head south for retirement.

Conversely, fewer than a quarter of homes built in the Northeast and Mid-Atlantic regions are single-story. Most are two-story homes.

Given that nationally 96% of houses are built on site, there are few differences among the nine regions. The percentages range from a low of 94% in the East North Central to a high of 98% in the Western states.

Nationally, three-quarters of new single-family houses are built for sale, but there are large differences among the nine U.S. regions. They range from a low of 52% in the Mid-Atlantic region, which includes New York, New Jersey and Pennsylvania, to a high of 85% in the South Atlantic, which covers the Eastern states from Virginia and West Virginia down to Florida.

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