A trend-spotting London property glossy says that gym-installation is the new topping out in cutting-edge urban building. Well, the Treet building is in place and the first residents are already working out. So the world officially has its new tallest timberbased residential block, in Bergen, Norway.
At the time of interviewing, project architect Per Reigstad of Artec, said the development was just being tidied up, with grounds being landscaped. But the full 14-storey, 49m structure was complete, beating previous timber building record holder, Melbourne’s Forte Tower, by 4-storey’s and 17m.
"By the time of the formal opening, 56 of the 63 apartments were sold, well within the target of developers Bergen and Bob Building society (BOB)," said Mr Reigstad. "Overall we were very happy with the outcome, except perhaps the timeframe of the project, and so clearly are the residents. While some issues still always come up with multi-storey timber building, such as durability, perhaps, and fire safety, Treet’s inhabitants were actively drawn to it: the more wood visible, the better they liked it."
As we’ll see below, he might have added to that final sentence, and the more they’d pay.
What stretched the building schedule was planning and the untried approach of the core timber structure; blending timber frame, CLT and glulam structural frame. The planning process started a decade ago, as Bergen town planners wrestled with a timber building the like of which they’d never seen. The preparations for the building itself began five years ago, and erection from foundations up a relatively inconsequential 1.5 years.
The other key players in the project were Scandinavian engineered timber specialist (CLT and glulam) Moelven, main contractor Sweco, and modular housing designer/ producer Kodumaja of Estonia.
What makes Treet even more groundbreaking than its scale, is the way the various skills and products of these businesses came together in a single structure.
Speaking at the International Softwood Conference in Amsterdam in November, BOB project manager Ole Herbrand Kleppe said this approach could provide an answer for potential height constraints on primarily engineered wood-based buildings, which most recent tallest projects have been.
"This form could possibly be limited by the weight of the material and the resulting compression factor in the timber," he said, explaining that Treet takes an equally sturdy, but very different approach.
It comprises four-storey stacks of timber and engineered wood-based apartment modules. These are then enclosed in a structural glulam frame, which effectively comprises a series of ‘upended bridge trusses’.
Next the fifth-storey comprises a glulamreinforced ‘platform’ floor fixed into the frame. Living in an apartment here, you really experience the wood. Heavy-duty glulam beams and struts jut into rooms, expressing the reinforcing role of this segment of the structure.
"This floor acts as the foundation for the next four storeys of modules, and the 10th storey comprises another platform, supporting floors 11 to 14," said Mr Kleppe. "Apartments on these levels are love them or hate them, but many loved them and they were among the first to sell, along with a great roof-terrace, and the sea-view apartments," said Mr Reigstad. "In fact, one buyer was so keen on the reinforced floors, he took the show flat at once, complete with furniture!"
He added that the design also overcame issues with movement of tall buildings in wind.
"We achieved this partly through the structure, but also by installing heavier service elements in the upper levels," he said.
Other key aspects of the building were also in wood, including the stairwells and lift shafts, which were lowered into place by tower crane in single, 5-storey lengths.
Due to Bergen’s testing northerly sea-front climate, Treet’s exterior is shielded in a mix of glass screening (over balcony fronts) and steel cladding.
Asked whether Artec would take a similar approach again, Mr Reigstad gave a qualified yes. "It was in some ways experimental, so we might use the same overall method, but modified to make it easier," he said. "I’d also like to see this system adopted in climates where the timber can be more expressed externally."
He added that his practice is also keen to use timber in other structures.
"In fact, partly as a spin off or TREET, we’ve put in a bid to build a large-scale, three-block student accommodation block in Bergen."
Mr Kleppe agreed a fine-tuned version of TREET would be potentially quicker and cheaper, with the structure effectively going into mass-production.
The system, he said, could then pose serious commercial competition for multistorey steel and concrete, with the added advantage of its environmental performance It’s inherently energy-efficient and stores large amounts of CO2 in the structure, 2,000 tonnes in Treet’s case.
Meanwhile occupants can pound the treadmill and pump iron nine-storey’s up a timber tower, taking healthy living to a whole new level as exercising in a wood structure is supposedly better for you and your heart. And they can enjoy that experience exclusively until 2017, when Vienna’s bid for the world’s tallest timber building, a 24-storey, 84 m twin-tower is due for completion, with an 18-storey student block at the University of British Columbia to follow not long after. Following Treet, timber living will still be on the rise.
