For the Type VB, 15,000-square-foot addition to Common Ground High School in New Haven, Connecticut, the project team chose a combination of CLT and glulam. CLT panels provide the tension surface (and final ceiling finish) in a revolutionary system of prefabricated stressed skin assemblies that span the upper classrooms and circulation spaces. Vertical CLT panels form bearing and shear walls throughout the building while glulam rafters and heavy timber trusses span a large ground floor multi-purpose space. A treated glulam bridge deck on laminated timber piers provides access from the upper campus. Assisted only by a mobile crane, a five-person assembly crew installed the entire primary structure and enclosure in just four weeks. A primary objective for this project was that the building itself would be an environmental exemplar that integrated new ecological concepts and building technologies in a clearly legible and potentially instructive way. The team chose mass timber for its many benefits, including renewability, sustainability, and carbon sequestration.