Led by strong growth in the office and retail segments, commercial property sales hit $401 billion through Oct. 18, outpacing last year’s $359 billion total, according to Real Capital Analytics, a New York based real-estate research firm.

Construction spending on office buildings, shopping centers and other private, nonresidential projects jumped 15.2 percent in August, the Commerce Department said last month.

There are some signs of slowing growth, analysts say, but nothing compared to the residential real estate market, where foreclosures and mortgage defaults are still rising rapidly, mainly from subprime mortgages extended to risky borrowers. Most economists forecast further declines in home sales and prices, making it “the most significant current risk to our economy,” Treasury Secretary Henry Paulson said last week.

The commercial market has not been dragged down by the residential mortgage mess because for the most part, buyers and sellers are more sophisticated, and they have more financial flexibility and resources to ride out credit-market turmoil, experts said.

“It’s a different animal than the nonresidential construction business with the direct relationship between banks and business leaders, not banks and homeowners,” said Bernard Baumohl, managing director of The Economic Outlook Group in Princeton, N.J.

If the broader economy stumbles, the commercial real estate market would be vulnerable to “credit-risk contagion,” Wheaton said. Already, the credit crunch that started in mortgages has spread to other markets, including the commercial market, with some sellers asking for more capital upfront when mortgage-backed assets are financing a transaction.