U.S. manufacturing expanded for the first time in four months, a trade group of purchasing managers said Monday, buoyed by an increase in new orders and more jobs. The Institute for Supply Management said that its index of factory activity rose to 51.5, up from 49.6 in August. Economists say a reading above 50 signals growth. The index had been below that threshold from June through August. The reading â€œwill boost hopes that some of the recent slowdown in economic growth was just a summer phenomenon,â€ Paul Dales, an economist at Capital Economics, said in a note to his clients. According to the report, a measure of new orders rose to 52.3, which was the highest reading since May, suggesting that production will increase in the coming months. Separately, the government reported Monday that builders spent more on home construction in August, but overall construction spending fell. The Commerce Department said that construction spending dropped 0.7 percent, as spending on commercial projects such as office buildings and shopping centers fell. The decline lowered construction spending to a seasonally-adjusted annual rate of $834.4 billion, nearly 2 percent above a 12-year low hit in February 2011 and half of what is considered to be healthy. Spending on residential projects rose 0.9 percent in August, pushing to a seasonally adjusted annual rate of $237.5 billion, the Commerce Department said. Spending on single-family homes increased in August for the fifth straight month, while apartment construction spending rose for the tenth month in a row, the department said.