A builder works on the roof timbers of a new home at a Persimmon Plc construction site for residential housing in Salisbury, U.K., on Wednesday, Sept. 19, 2012. Persimmon, the U.K.'s largest homebuilder by market value, widened its operating margin to 12.2 percent in the first half from 9 percent a year earlier. Photographer: Simon Dawson/Bloomberg via Getty Images