The size of new single-family homes completed declined last year, dropping to a nationwide average of 2,438 square feet, according to detailed information about the characteristics of new homes completed in 2009 that was released recently by the Census Bureau.

After increasing continually for nearly three decades, the average size of single-family homes completed in the United States peaked at 2,521 square feet in 2007. It was essentially flat in 2008, then dropped in 2009, so that new single-family homes were almost 100 square feet smaller in 2009 than in 2007.

“We also saw a decline in the size of new homes when the economy lapsed into recession in the early 1980s,” said NAHB Chief Economist David Crowe. “The decline of the early 1980s turned out to be temporary, but this time the decline is related to phenomena such as an increased share of first-time home buyers, a desire to keep energy costs down, smaller amounts of equity in existing homes to roll into the next home, tighter credit standards and less focus on the investment component of buying a home. Many of these tendencies are likely to persist and continue affecting the new home market for an extended period.”

In keeping with their slightly smaller size, new single-family homes completed in 2009 had fewer bedrooms than previously. After increasing for almost 20 years, the proportion of single-family homes with four bedrooms or more topped out at 39 percent in 2005; it was 34 percent last year. The proportion of single-family homes with three bedrooms increased from 49 percent to 53 percent between 2005 and 2009.

New single-family homes completed last year also had fewer bathrooms than previously. The proportion of homes with three or more bathrooms was 24 percent last year, a decline from the peak of 28 percent in both 2007 and 2008. The percentage of single-family homes with two bathrooms increased from 35 to 37 last year, and the percentage with 2 1/2 bathrooms was at 31 percent for the third consecutive year. The proportion of single-family homes with 1 or 1 1/2 bathrooms has been below 10 percent for more than a decade.

In 1973, the first year for which the Census Bureau reports characteristics of single-family homes completed, most new single-family homes — 67 percent — had only one story. Twenty-three percent had two or more stories, and 10 percent were split levels.

The proportion of one-story homes declined steadily for more than three decades, dropping to a low of 43 percent in 2006 and 2007. At the same time, the proportion of single-family homes with two or more stories increased, rising from 23 percent in 1973 to a high of 57 percent in 2006 (split-level homes currently account for less than one percent of all single-family homes). Since 2006, the trends have been reversed, as the share of single-family homes with one-story increased to 47 percent last year, while the share with two or more stories dropped to 53 percent.