Local voters approved a property tax increase to pay for a new roof on the Elmwood School by a ratio of better than 3 to 1 in a special election Monday. The 404-112 vote supporting the Proposition 2½ debt-exclusion override came after Special Town Meeting on Nov. 26 had also approved the $1.1 million expenditure. The project will cost the owners of a single-family home with the town’s average assessed value, $474,038, an additional $26.46 during the first year of the 10-year bond. Local officials said the 24-year-old roof on the elementary school has been leaking for the past few years, causing water damage. Work to replace the roof is expected to be done over the summer.