ByJohn S. McClenahen Bettering economists' expectations and buoyed by low interest rates on home mortgages, the value of all U.S. construction put in place during October was at a seasonally adjusted annual rate of $834.6 billion, 0.2% higher than September's level, reports the U.S. Commerce Department. Single-family units were up 1% from September to $265.9 billion and 6% higher than the previous October's mark. Industrial buildings, offices and other kinds of private nonresidential construction totaled $158.3 billion in October. Nevertheless, "we expect overall construction spending will be a slight negative for fourth-quarter GDP growth," says Gerald D. Cohen, a senior economist at Merrill Lynch & Co., New York.