Fourteen storeys tall with a breath-taking view of the harbour city of Bergen and the surrounding fjord landscape – the “Treet”, which will be completed in November 2015, is an impressive structure. In fact, the 51 metre-high “tree” is the tallest wooden apartment building in the world. It is being built by BOB BBL, which is one of Norway’s largest corporate housing association with its inventory of 22,500 domiciles. Teknos also has a hand in this groundbreaking project with its fire-retardant coatings for both interiors and exteriors.
The Treet is designed with a supporting wooden frame structure made of gluelams and pre-fabricated, stackable building modules. The modules are prefabricated, complete with insulation, flooring and electrical wiring, and stacked on top of each other at intervals of four storeys. Every fifth storey is reinforced with glulam girders to make a platform for the next four storeys of apartments. On top of the platform concrete elements are used to give extra weight, to improve its tructural integrity. Glass facades to the north and south, as well as weatherproof Corten steel to the east and west, reliably protect the wooden structure from moisture.
The building is located on the 4,600 square metre premises at Puddefjord and consists of 14 storeys with 62 apartments between 43 and 66 square metres each. At the ninth floor there is a fitness centre with panorama windows. A rooftop terrace, with a view over the Norwegian harbour metropolis, further increase the property’s value.
The use of prefabricated modules is a major part of the concept. “The high level of prefabrication reduces construction times and is simultaneously more cost-effective and environmentally friendly,” explains BOB project manager, Ole Kleppe. “Modern urban construction means intelligent use of space with sustainable materials, and our project shows that this can definitely be achieved with wooden structures.”
Predominately prefabricated laminated timber elements are used for stairways, stairs, elevator shafts, landings and balcony panels. These were delivered and precisely installed by Moelven Limtre, a market-leading Norwegian
timber specialist. The majority of the elements were produced in Germany by Merk Timber, a subsidiary of Züblin.
Fire safety is a crucial factor in timber buildings. And that holds especially true for the tallest wooden building in the world. Moelven Limtre has long relied on Teknos products and has once again opted for an innovative solution from Teknos for the Treet’s fireretardant coatings. The gluelam construction elements for the road and fjord sides were coated with the fire-retardant coating TEKNOSAFE 2407 directly at the Moelven factory. TEKNOSAFE 2407 foams up when subjected to heat, creating an insulating layer made of microporous carbon foam, which effectively insulates the treated wood against heat. In contrast to borate-based fire protection impregnations, TEKNOSAFE 2407 does not absorb moisture, which makes it less vulnerable to losing its effect from weathering. The elevator shafts and other concealed elements are treated with the fire-retardant coating TEKNOSAFE 2407.
The visible surfaces of the laminated timber elements on the interior are treated with the new
TEKNOSAFE 2467-00 and TEKNOCLEAR AQUA 1331 clear coating. TEKNOSAFE 2467-00
also works as a foaming, insulating layer in the event of fire.
The highly transparent clear coating provides protection from dirt, especially in the heavily frequented stairways.
The interior surfaces were treated on site. Teknos application technicians trained the craftspersons who performed the work at the construction site and equipped them with special instruments to measure the wet film thickness. This is because the certified fire-retardant effect of TEKNOSAFE 2467-00 requires a wet film thickness of 200 μm, while the proper application of the whitepigmented coating ensures an even surface with an attractive wood appearance.
A template for urban living “Treet is a flagship project in which we make use of innovative, intelligent solutions,” says BOB project manager, Ole Kleppe. “It combines Norwegian timber construction tradition with modern Scandinavian design. As a residential building, the Treet offers the benefits of an energy-efficient, passive house with the healthy indoor climate of a wooden structure.”