Home building slowed to a near-halt in Palm Beach County and the Treasure Coast in the third quarter. Housing starts fell to their lowest level in at least a decade, and high inventory levels prompted builders to cut activity by as much as 90 percent. Housing research firm Metrostudy said housing starts are at their lowest level since it started keeping records in the 1990s. In Palm Beach County, builders started 245 single-family homes in the third quarter, compared to 488 starts in the second quarter, Metrostudy said. Earlier in the decade, builders routinely broke ground on more than 2,500 homes a quarter.