Heavy timber hasn’t been used as a major new office building construction material in D.C. for a century, but a shiny glass and brick office building at Capitol Riverfront will get two additional stories constructed of environmentally-friendly mass timber.

The addition, and a usable penthouse, will be built atop the existing 286,000-square-foot 80 M Street building.

Construction hasn’t started yet, but building owner Columbia Property Trust has already lined up a tenant: The American Trucking Association has signed a 16-year lease for 60,000 square feet, or more than half the 105,000 square feet the addition will add.

The association, the largest national trade association for the trucking industry, will make the move from its current Arlington headquarters to its new timber-framed Capitol Riverfront home in 2022.

Columbia Property says 80 M Street will be the first commercial office building in D.C. to feature mass timber new construction.

The construction material will consist of a composite wood product engineered from hard wood grown in the Pacific Northwest. It says mass timber provides structural integrity and fire resistance comparable to steel and concrete, but with lower weight and a lower carbon footprint.

D.C. architectural firm Hickok Cole designed the addition. It will also include 4,000 square feet of outdoor space.