NEW YORK (CNN/Money) - Cement prices are up as much as 20 percent from year-ago levels, due to shortages brought on by a boom in home construction and import constraints, according to a published report.

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The Wall Street Journal reported Monday that surveys by the Portland Cement Association, an industry group, shows shortages in at least 30 states. Particularly hard hit areas include the Sunbelt, from Florida to California, but there are some reported shortages in the Northeast and upper Midwest as well.

Economists told the paper the larger economy could be affected if there are not improvements in supply constraints soon. Cement-makers say their plants are running close to full capacity. Rapid growth in China has prevented builders from turning to foreign suppliers to make up the difference as they normally due. The growth of demand in China has tied up cargo ships and prompted spikes in freight rates that made transport prohibitively expensive.

The shortages are compounded by U.S. rail backlogs.

Cement, a key component of concrete, is not the only building raw material seeing price hikes. Framing lumber is up 52 percent from year-earlier levels, according to the Journal. But the cement shortages are causing delays in some projects and could force some contractors, especially smaller builders, to lay off staff because they don't have the product necessary to complete jobs.