Mark Olsen, chairman of the B.C. Building Trade Unions, says the deal is important for projects such as the multibillion-dollar Site C hydroelectric dam.
There are also a number of planned mining, pipeline, marine terminal and liquefied natural gas projects.
Members of 16 trade unions voted on the deal, which Olsen says will keep the labour climate stable.
Rob Tuzzi, the bargaining council's secretary-treasurer, says companies involved in large construction projects typically look to unions to help them recruit the workers they need.
Olsen says the deal extends current contracts for more than 40,000 workers to the end of next April, and negotiations for contracts beyond that date are to begin later this spring.