The world’s tallest wooden tower
Opened on 15 March, the Mjøstårnet, or the Mjøsa Tower in Brumunddal near Oslo, Norway, is with 85.4 metres currently the world’s tallest wooden building.
While wood was one of the first building materials used by men, its use fell out of favour because of it being known as a fire hazard. However, with the downsides of building materials like bricks, concrete and metal becoming more evident, more and more people are turning back to wood. Not the type of wood that grows on trees, though, but engineered wood that is stronger and less flammable.
Designed by Voll Arkitekter, the 18-storey tower is made from lightweight, prefabricated materials, mainly glulam (glued laminated timber), CLT (cross-laminated timber) and MetsäWood’s Kerto LVL (laminated veneer timber), produced in Finland. Kerto LVL is lightweight, strong, and uniform and has an “outstanding strength-to-weight” ratio.
Both the structure and the façade of the Mjøsa Tower are made of wood. The first ten floors, with offices and hotel facilities, are made of prefabricated wooden elements. The decks on the upper floors, however, where apartments are made of concrete. This is because the amount of swaying increases the higher you get in a building built of wood or concrete. The weight of the concrete makes the swaying slower and not as noticeable. The shafts for the elevators and staircases are made of CLT.
The tower, located next to the eponymous largest lake of Norway, was built according to strict fire safety regulations. Untreated solid wood creates its own fire-resistant surface because the outermost layer chars when exposed to fire, protecting against further fire damage. Massive wooden structures manufactured in large maintain therefore their load-bearing capacity in case of fire.
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By Els Zijlstra
Photos: Voll Arkitekter