Close to both the sea and the city, the world’s tallest wooden building rises to a height of 51 metres. A home in “Treet” – the tree – offers airy, high-quality living space based on spruce from deep Norwegian forests.
The Treet residential building in Bergen comprises 14 storeys in wood and is a full four storeys taller than any other wooden building in the world. Not only is it unique, it is also historic.
‘It’s been a global race, with many countries voicing their intention to build a tall wooden building. But Norway got there first, putting Bergen on the map among architects and experts the world over,’ says Rune Abrahamsen, graduate engineer and Norway’s leading specialist in glulam and wooden load-bearing constructions. Employed by Sweco at the time, he was the consultant engineer in the building project and one of the brains behind the innovative building.
It’s not just the size but also the building method that makes the building ground-breaking: Using glulam in combination with modules, as has been done in Treet, is something completely new. The building has been constructed by stacking modules to make the first four storeys, followed by a reinforced storey with glulam structures and a concrete slab on the top as the basis for another four storeys, before another supporting platform on the tenth storey.
‘This is where the innovation lies. We established a building system for wood that functions for great heights. This hasn’t been done for housing purposes previously, so there wasn’t much to lean on,’ says Abrahamsen, pointing out that the challenge is that wood is a light material and can oscillate significantly at height.
The planning group made up of representatives from the main contractor and subcontractors – a dedicated development team – worked with academics at the Norwegian University of Science and Technology (NTNU) to test and calculate the damping factor.
‘A tall wooden building can be compared to a blade of grass. When it’s windy, there is movement, and it would have been uncomfortable living in the top storeys.’
Physical testing and estimates assessed the damping factor for Treet to be 1.9. After the building was constructed, it was measured at an impressive 1.89.
‘It must be said there have been many clever people involved in this work and many high-powered brains behind the various parts of the project,’ says Abrahamsen, who acknowledges he is pleased to have taken part.
‘It was an incredibly exciting process that culminated in a successful project – a building containing a lot of wood in which it is pleasant to live and people can enjoy a good quality of life,’ he sums up.
Large span Rune Abrahamsen is now manager of Moelven Limtre, which also made a significant contribution to the process, both in terms of innovation and deliveries. The 45 metre trusses, partly visible both inside and outside, were produced and assembled by Moelven Limtre AS.
‘These were enormous frame works, delivered with millimetre precision,’ he states.
Abrahamsen believes using wood in buildings affects how people experience the building, and gives it distinctive characteristics.
‘We Scandinavians have long traditions of building with wood. We’re used to wooden houses: they make us feel comfortable, we like the smell and I think many people find them warm. Quite simply, wood changes the whole atmosphere of a building and the indoor climate,’ he says.
Special indoor environment
Entrepreneur Bjørn Myreze has bought one of the 62 flats in Treet. As well as the great location and functional living space, he cites the indoor environment as a particular attraction.
‘The first thing that struck us as we came into the building was the fresh air,’ says Myreze, who explains that they had originally intended to buy a flat on one of the top storeys.
‘Instead, we chose the ground floor. We fell in love with the flat as soon as we walked into it. We’d never imagined it would be possible to live so close to the sea but here we’re almost living on the water, rather like being on a boat,’ he says.
He thinks the fact that the house has been built in wood makes a big difference in how it is perceived.
‘Even outside, the wood is the first thing you are aware of and, with wooden structures and surfaces inside, the whole building seems to breathe. The balance between wood and modern technology has produced a fantastic building that is also environmentally friendly, with a top energy rating of A under Norway’s Energimerke scheme. And you get both sea and city views into the bargain,’ he comments.
More high wooden buildings in prospect
Rune Abrahamsen believes Treet will just be the starting shot when it comes to constructing high wooden buildings.
‘We’re already seeing more and more people moving to the cities, and this trend will only increase in the future. Space in urban areas is in short supply, and one way of using the space better is to build “up”. High wooden buildings in cities are the ultimate answer to meeting the environmental requirements of the future and being able to build sustainably,’ he states, adding that the problems are even more acute in countries with higher population densities.
Treet has provided much valuable experience, and every week Abrahamsen receives enquiries about the building from all over the world – from students, publications and industry insiders wanting more information and a guided tour.
‘I can’t accommodate every request, but there have been a number of guided tours of the building, most recently with a delegation from France,’ he relates.
Being involved in innovative development projects is a high priority for Moelven Limtre.
‘In terms of both hours and expertise, we devote quite a lot of resources and people to being innovative in projects. We want to be out in front all the way, and not just in Norway, but internationally too,’ he states.
A new, ground-breaking landmark building in wood is now ready on the drawing board. Flats in the 18-storey Mjøstårnet building in Brumunddal near Moelven, which will rise to more than 70 metres, are now up for sale.