Watch: Mjösa Tower - the worlds tallest wooden building

Designed by Voll Arkitekter and built by Moelven Limtre, bimstore manufacturer, Metsä Wood's Kerto-Q LVL was integral to the projects specification.

The tower houses a mix of homes, offices and hotel rooms, all built using primarily regional materials and sustainably sourced timber. The floor elements were made using glulam and Metsä Wood's Kerto® LVL (laminated veneer lumber), a fast, light, green material produced in Finland.

It’s lightweight, yet strong enough to withstand the challenges that come with an 85.4-metre building. In addition, Kerto LVL is uniform and has an outstanding strength-to-weight ratio – in short, the perfect solution for a structure that’s a pioneer in sustainable urban architecture.

We want to inspire others to build the same way.

The design approach used for the Mjösa Tower is firmly rooted in the Norwegian tradition of using wood in architecture to stand the test of time.

“We want to inspire others to build the same way,” says Øystein Elgsaas, architect and partner at Voll Arkitekter, the agency that designed the Mjösa Tower.

To design a tall building using wood was a positive challenge for Elgsaas. The load-bearing structure is similar to conventional buildings, but the dimensions of the elements are much larger than usual: The wooden columns were 60 × 60 centimetres on average, and the largest ones used in the corners were almost 60 × 150 centimetres.

“We had to find a narrow plan layout, which both provides room for different kinds of spaces and ensures the columns are not too dominant in the interior, but we achieved it,” says Elgsaas. The building won the prize for best mixed architecture at the 2018 New York Design Awards.

Both the “skeleton” and “skin” (i.e. the structure and facade of the Mjösa Tower) are made of wood. The structure consists of glulam columns, beams and diagonal members, which are well-suited to high-rise buildings as the large cross-sections can meet fire safety requirements.

The first ten floors, with offices and hotel facilities, are made of prefabricated wooden elements – and that is where Kerto LVL Q-panels from Metsä Wood provide stiffness. Kerto LVL is combined with glulam.

The decks on the upper floors, with apartments, are made of concrete. The weight of the concrete makes swaying at height slower and not as noticeable. The shafts for the elevators and staircases were made of CLT.

It guaranteed production without any delays.

Kerto LVL Q-panels were easy to process as a component of the prefabricated wooden elements at Moelven Limtre’s factory. Some of the Q-panels were pre-cut and sanded beforehand at one our collaborator’s factories.

“Kerto LVL is a lightweight and very straight material; thus, it guaranteed production without any delays. The quality of the product is very good,” says Rune Abrahamsen, CEO at Moelven Limtre. Cross-laminated Kerto LVL also has a great strength-to-weight ratio.

Lightness was a benefit in the assembly phase as well. As all elements were prefabricated and light to handle, the structure grew by almost one floor every week.

Throughout the process, sections of the building were built within a factory before being moved to site and fixed to one another, proving to be both time and cost efficient. 

The Mjösa Tower has been built according to strict fire safety regulations. The whole building has a sprinkler system. Untreated solid wood creates its own fire-resistant surface because the outermost layer chars when exposed to fire, protecting against further fire damage. To sum up, massive wooden structures manufactured in large dimensions are a good choice as they maintain the load-bearing capacity in case of fire.

In addition, each floor has been built as an individual compartment. The floor elements – including Kerto LVL and glulam – have a 90-minute fire resistance. These elements have been upgraded with brackets so fire cannot get to the hollow areas.