The data come from the Survey of Construction (SOC, conducted by the U.S. Census Bureau with partial funding from HUD). Although the SOC has always collected data on 3-story single-family homes, the Census Bureau began publishing information on them only recently. Traditionally, the three categories in Census publications have been one-story, two or more stories, and split-level (a structure with floors on more than one level when the difference in some floor levels is less than one story).
However, split-level construction dropped from over 10 percent of single-family completions in the late 1970s, to less than one half of one percent by 2005. As a result, a few years ago, the Census Bureau began lumping split-level in with two-story homes and reporting a separate category for 3-plus story in its reports on characteristics of new homes completed. The latest of these reports shows 3-plus story homes accounting for about 3 percent of single-family completions in the depths of the housing downturn in 2009, increasing to about 5 percent by 2013. Since 2013, the share has remained relatively constant, with the number of new 3-plus single-family homes growing in proportion to overall completions.
In 2017, just under 800,000 new single-family homes were completed, and 42,000 of these had three or more stories. The Census definition of a story is simply that portion of a home between the floor and ceiling or roof. A basement never counts as a story (even if its floor, ceiling and walls are completely finished).
It is reasonably well known that single-family attached structures, or townhomes, with three or more stories are built as a matter of routine in some parts of the country. A more interesting question is whether or not any new single-family detached homes have 3-plus stories
Published Census reports don’t provide that detail, but detached structures can be tabulated separately using the publicly available SOC data files. Data on 3-plus story homes first became available in the public SOC file for 2016. The basic counts tabulated by NAHB from the 2016 and 2017 files are shown below.
Note that, although the Census Bureau publishes characteristics for homes completed in a given year, NAHB prefers to report data on homes started, primarily because starts are emphasized so heavily in media reports on new construction. As the chart shows, some 3-plus story single-family detached homes are indeed being built. In 2016 and 2017, the number of 3-story single-family homes started was split roughly evenly between townhome and detached structures.
The main difference is that the 18,200 3-plus story single-family detached homes started in 2017 account for only 2.5 percent of all single-family detached starts. In contrast, the 23,000 3-plus story townhomes represent 22.0 percent of single-family townhome starts. Compared to 2016, the number of 3-plus story single-family townhomes was up in 2017, and the number of 3-plus story single-family detached homes was down. The year-to-year differences were relatively small, however, and two years of data are not enough to establish a trend.
The public SOC data file can also be tabulated by the nine Census divisions:
As the map shows, the greatest numbers of 3-story single-family detached homes were built in the South Atlantic Census division in 2017, followed by the Pacific, Mid Atlantic and West South Central. The geographic breakdown for 3-story single-family townhomes is similar, except that new 3-story townhomes are even more heavily concentrated in the South Atlantic division, are somewhat less common in the West South Central, and somewhat more common in the Mountain states.