Rising on the shore of Lake Mjøsa, the 18-floor Mjösa Tower is a record-breakingly tall, lightweight and streamlined wooden building. The construction of this entirely new kind of building required everyone involved to have the courage to do things differently. These efforts also gave rise to new wood construction design expertise.
Mjösa Tower is located on the shore of Norway’s largest lake, Mjøsa, in the small town of Brumunddal, approximately 140 kilometres from Oslo. The idea for the tower came from the founder of AB Invest, Arthur Buchardt, who owns the building together with his son, Anders Buchardt.
“Mjösa Tower is an excellent display of the potential of wood construction,” summarises wood building specialist Magne Bjertnæs from Sweco. The approximately 11,300-square-metre, 18-floor and 81-metre-tall tower includes housing, offices, a luxury hotel and a restaurant with a roof terrace. Construction began in 2017 and was completed in spring 2019.
“Mjösa was a fascinating and demanding project with strict timetables, as well as a great example of the cooperation between Sweco’s different offices,” Bjertnæs says.
A stable high-rise can be built out of wood
Mjösa Tower uses a glulam column and beam structure as the main bearing. The slabs are made with Moelven’s Trä8 slab system, which enables spans of up to 8 metres in the intermediate floors. This is an ideal system for the types of buildings that have been traditionally built out of steel and prestressed concrete.
“The glulam structure enables open space solutions, while also making the structure rigid enough for tall construction,” Bjertnæs states. Stability is always a challenge with tall buildings. “This project taught us a great deal about the dynamic properties of slender and lightweight wooden buildings.”
Challenges related to stability were also tackled by increasing the weight of the building. The first 10 floors are made entirely of wood, but the intermediate floors of the 8 highest floors are made out of concrete. “The lessons learned and experience gained in this project will undoubtedly reduce the risks affecting different parties in future high-rise projects,” Bjertnæs says.
Mjösa contains 2,600 cubic metres of wood
Mjösa Tower is a model example of efficientyet responsible urban construction. Material efficiency, long life-cycle and easy maintenance were considered in all of the building’s solutions. For example, the building’s load-bearing wooden structures are protected from rain and sunlight behind the wooden facade and glass elements.
A total of approximately 2,685 cubic metres of wood was used in the construction, and the frame structure was constructed insofar as possible at the factory under controlled conditions. The intermediate floors consist of a combination of Moelve’s glulam beams and Kerto® LVL Q panels. ”Kerto LVL is a very strong, lightweight and dimension-accurate material for rapid construction,” summarises Metsä Wood’s Director of Technical Customer Service Jussi Björman.
The approximately 74-metre-tall lift and staircase shafts were made out of Stora Enso’s CLT elements. During construction, it took only about two weeks to finish an entire floor. The total time is 9 months on 18 stories. “Due to the light weight of wooden structural parts, we did not need any heavy machinery, which shortened the construction time by 35–40% compared to on site concrete construction,” says Moelven Limtre AS’s CEO Rune Abrahamsen.
Pictures: Metsä Group