PORTLAND, Oregon — When Carpenters Local 1503 member William Smith got a chance to work reconstructing the Portland International Airport’s main terminal, he left another job to take it. That’s because of the project’s centerpiece: A mass timber roof made from Oregon-sourced wood. …Beyond the technical novelties, Smith liked the longevity of the finished product. …Other union workers on the job feel the same. …The terminal roof is part of a five-year $2 billion upgrade that started in 2021. Building and installing the roof is a year-long phase of the terminal work, finishing late this year. Work will then pivot to the terminal’s interior. …Carpenters receive prefabricated wood components that they assemble and move into place, another feature of mass-timber construction. Swinerton worker Nick Phelan, a Carpenters Local 1503 member, says it’s like assembling a giant piece of IKEA furniture.