Rising in the Norwegian town of Brumunddal, Mjøstårnet was, on completion, the world's tallest timber building (85.4 m, 18 storeys). Its importance is less its height than what it proves: that wood can be a serious alternative to steel and concrete in the tall building.

The building's load-bearing system rests on engineered timber. The main columns and diagonal braces are glulam (glued laminated timber) elements — made by gluing thin wood lamellae parallel to the grain — which can be as strong as a steel beam. The floors and wall panels are made of cross-laminated timber (CLT): by gluing layers of wood crosswise on top of one another, large structural boards stable in both directions are obtained. These prefabricated timber parts were made in the factory and quickly assembled on site.

The two known weaknesses of wood — fire and sway — were specifically resolved: thick mass timber was dimensioned so that in a fire the outside chars while the inside stays load-bearing; weight (concrete floors) was added to the upper storeys to prevent excessive sway in the wind. Mjøstårnet thus becomes the pioneering proof of the "return to timber" in architecture, showing that a carbon-storing, renewable material can be load-bearing at skyscraper scale.