Architecture

Norwegian timber tower will reach new heights

Norwegian timber tower will re...
Once completed, Mjøstårnet will comprise over 11,300 sq m (121,632 sq ft) of floorspace, spread over 18 floors
Once completed, Mjøstårnet will comprise over 11,300 sq m (121,632 sq ft) of floorspace, spread over 18 floors
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Mjøstårnet is due to be completed in March, 2019
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Mjøstårnet is due to be completed in March, 2019
Mjøstårnet will rise to a height of 81 m (265 ft) once complete, probably making it the new world's tallest wooden building
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Mjøstårnet will rise to a height of 81 m (265 ft) once complete, probably making it the new world's tallest wooden building
Once completed, Mjøstårnet will comprise over 11,300 sq m (121,632 sq ft) of floorspace, spread over 18 floors
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Once completed, Mjøstårnet will comprise over 11,300 sq m (121,632 sq ft) of floorspace, spread over 18 floors

Following our coverage of a tall wooden tower that might get built, here's one that is being built. Named Mjøstårnet, it's currently under construction in Norway and will rise to a height of 81 m (265 ft) once complete, making it the new world's tallest wooden building. Kind of. Maybe. That depends on rule changes which may or may not come into force. Either way, the project offers some insight into the challenges of tall timber construction.

As things stand, the world's tallest timber tower will be Vienna's 84 m (275 ft) Ho Ho Tower once it's complete. However, the influential Council on Tall Buildings and Urban Habitat, which keeps track of such things, is set to bring in new rules to the effect that buildings like the Ho Ho, which have a concrete core, be defined as wood-concrete hybrid structures.

Mjøstårnet has no such concrete core, instead relying on glulam beams for structural support, thereby making it the tallest wooden building if the changes do indeed come into place. Whatever happens, the record may not stand for long anyway in this fast-moving area of architecture.

Mjøstårnet will comprise over 11,300 sq m (121,632 sq ft) of floorspace, spread over 18 floors. The building will include residential units, a hotel, restaurant, offices, and common areas, plus a large swimming hall.

For those thinking that it'll be a tinder box, Moelven Limtre, the firm in charge of the project along with Voll Arkitekter and Sweco, indicates that such fears are unfounded and that any fire would die out by itself even if the sprinkler system fails, leaving the building structurally sound.

"The requirement has been that the building must remain standing after an eventual fire has gone out by itself – even if the sprinkler system should fail and without extinguishing," says Moelven Limtre's CEO Rune Abrahamsen. "An independent fire test has documented that the strong glulam structures will continue to support the building after a fire has gone out by itself. We have calculated the location of the glulam beams such that they don't mutually affect each other in the event of a fire. The amount of flammable material at any location will be so small that a fire will die out by itself."

Mjøstårnet will rise to a height of 81 m (265 ft) once complete, probably making it the new world's tallest wooden building
Mjøstårnet will rise to a height of 81 m (265 ft) once complete, probably making it the new world's tallest wooden building

The bigger issue in this project actually seems to be swaying in the wind, and the potential for residents in the upper floors to experience the unpleasant sensation of motion sickness.

"Tall wood buildings sway somewhat more than those built from steel and concrete due to a far lower weight," adds Abrahamsen. "This applies in particular to a narrow building such as Mjøstårnet with a width of just 16 m [52 ft]. For this reason we are using concrete slabs for the top seven floors. Swaying at high winds has been calculated to around 14 cm [5.5-in] at the top. The effects are the same with or without concrete slabs, but the greater weight towards the top means that swaying will be slower, thus preventing 'seasickness' among residents."

Work on the project began in April 2017 and it's expected to be completed in March, 2019.

Sources: Moelven, Voll Arkitekter

6 comments
Sisko
If the building sways more and faster then a non (or not totally) wood building, what is the advantage of making it from wood? Is it just a proof of concept?
Joshua Tulberg
I too would like to know the advantages of building a tower in wood.
Naum Shuv
@Sisko @Joshua Tulberg The advantages are obvious. Zero carbon emissions, for example. Besides, you can hoist prefabricated units, not just ordinary elements with an ordinary crane. Imagine apartments with all plumbing and cables being produced at factories. There was an article about such a wooden prefabricated units on this site. Still I cannot understand the use of these concrete slabs... Can't the architects design some kind of rigid areas in the building, instead of adding more weight?
ljaques
That's some truly impressive glulam beam work, but I have a bad feeling about wooden towers. I'd sure love to see the architect's "building longevity" figures. Wood is great, but I wouldn't ever enter the finished building. Expect to see these towers last less than a generation, or abandoned earlier after a catastrophic failure.
ei3io
Wood is superior to steel and concrete in so many ways while it can still use minimal concrete/steel stair and elevator shafts for rigidity when avoiding heavy diagonal braces. Wood lasts for unlimited centuries if kept dry or wet with no oxygen as in ancient deep piles. Its fireproof capabilities exceed steel and concrete when detailed properly and it locks up carbon when not allowed to rot in the forest. Mass Timber will be big part of the future.
john75
Now THAT is post and beam construction. Wood is just as strong as steel by weight but is much bulkier for a given weight. While it is slightly carbon negative it's able to supplement or supplant steel manufacture which is very energy intensive and concrete which is at least as energy intensive as steel. Wordlwide, concrete production is actually the biggest anthropogenic source of CO2 aside from livestock, even worse than the transportation sector. I'm not sure how well these structures would fare against a jet fuel fire but few if any structures would do well anyway. The climate may ensure that insects will never be a problem but it would be interesting to know if that would be true in a more temperate or even tropical area. Very neat.