After seeing photographs of striking Lumber 4 office building, my immediate reaction was to look up Lumber 1, 2, and 3. A glimpse of the elegantly scalloped and vivid green facade had me wondering how just much more of this stuff Oslotre had in their locker. And while researching the Norwegian architects and mass timber consultants yielded an impressive array of projects, a numerical sequence of lumbers was conspicuously absent. As it turned out, “Lumber” isn’t a reference to wood design, but rather the building’s neighbourhood in the city of Kristiansand.

Luckily for us English-speakers, the name works on two levels. On the southeast coast of Norway, the six-storey, 3,106-square-metre Lumber 4 office complex is both a neighbourhood icon and a conspicuous showcase for the global possibilities of mass timber design. Built to serve as a commercial hub targeting tenants with a sustainable focus, the building — which forms an extension of a pre-existing office complex — integrates a range of evolving wood technologies into a stylish setting.

Columns and beams made from glued laminated timber (glulam) are complemented by a floor system fabricated with a composite structure of Cross-Laminated Timber (CLT) and concrete. The hybrid, partially prefabricated system allows for a slim, spatially efficient and reasonably sound-absorbing profile that facilitates reasonably long spans and open floor plates, resolving a chronic hindrance of mass timber floors. Meanwhile, the building’s connection to the pre-existing concrete office complex ensures added lateral stability.

Throughout the interiors, a simple exposed spruce structure is paired with wood-wool acoustic panels (mitigating the high noice transfer typical of mass timber buildings) and visible ducts, which were painted a subtle beige to blend in with the organic wood interiors.

Throughout the building, wood provides both an innovative structural tool and an aesthetic identity. The focal point is the scalloped facade, deftly cantilevered above a compact, spatially efficient rounded base. Composed of prefabricated pine elements, the curved walls were painted forest-green. As the building ages, the colour will take on a patina, amplifying a sense of depth already apparent across the facade thanks to the interplay of curved walls and the shadows cast by the straight and slightly extruded eaves of the floor-to-ceiling windows.

The combination of mass timber and prefabricated technologies allowed Lumber 4 to be constructed over a period of just 12 months. According to the designers, it also made for a 53 per cent reduction in upfront carbon costs compared to a typical concrete building of the same scale. For Oslo-based Oslotre, the firm’s holistic role as both architects and interior designers — as well as timber structural engineers — helped ensure an even more streamlined process. Here’s to Lumber 5, 6, and 7.