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Sky’s the limit for timber skyscrapers

2 March 2018

Views from the ninth floor of Moelven’s 81m Mjøstårnet

Norwegian timber specialist believes timber towers could hit 150m as the technology develops.

The claim to be the tallest timber tower in the world currently belongs to Brock Commons, a 53m-high student residence at the University of British Columbia, in Vancouver, Canada. It will, however, shortly be eclipsed by other structures rising in Europe.

Brock Commons, like other high-rise buildings with timber structural components, in fact uses a hybrid construction methodology. The 18-storey tower uses glulam columns which support CLT floor panels, with steel connectors at the intersections, plus a concrete foundation and two concrete stair cores.

Meanwhile, the two towers of the HoHo building in Vienna will rise to 24 storeys and a height of 84m on completion later this year.

Around three-quarters of the structure is being constructed from timber, with wood-composite floors secured to central concrete cores, and supporting timber columns around the building’s perimeter. External wall modules, made from concrete shells and solid wood panels, form the building’s facade.

In December, Norwegian timber specialist Moelven announced it is building Mjøstårnet, an 81m-tall mixed-use tower in Brumunddal, 100km north of Oslo, though again it is a hybrid.

Director Rune Abrahamsen – also responsible for the residential development Treet in Bergen, which was constructed in 2015 and previously held the world record for the tallest timber building at 51m – believes that timber skyscrapers can go past the 150m mark.

The Mjøstårnet structure will be built using CLT, glulam and laminated veneer lumber. Abrahamsen explains that because Mjøstårnet is a narrow building, with a width of just 16m, Moelven is using concrete slabs for the top seven floors.

“Tall wood buildings sway more than those built from steel and concrete due to a far lower weight, and swaying at high winds has been calculated to be around 14m at the top,” he says.

“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.”

With a larger building footprint, Abrahamsen believes that it will be possible to build timber buildings considerably taller.

“It’s mainly the width that determines how tall we may build a timber building,” he says. “Greater width means the building sways less. A wider building would make it unproblematic to build higher than 100m, and even perhaps 150m.”

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