Perched on the side of Mount Fløyen, 1,000 feet above Bergen, Norway, Tubakuba is a tiny mountain cottage designed to immerse occupants in nature just minutes from the city center. It was completed in the summer of 2014 by the Bergen School of Architecture (BSA), under the supervision of instructor Espen Folgerø, who is also a designer with local firm OPA Form Architects.
Timber is plentiful in Norway, and wood holds much significance, culturally and environmentally. The design team, which conceptualized and pitched the project to the city, wanted guests to intuitively understand that importance along with its beauty, versatility, and ability to sequester carbon. “If you chop down timber at the right point in [a tree’s] growth period, you’re going to store the carbon inside the timber as opposed to it going into the atmosphere,” Folgerø says.
Ninety-five percent of Tubakuba is constructed from wood, pieced together from three types of timber. The interior, including the flooring and two curvilinear benches for sitting and sleeping, is mostly plywood made from Scots pine (Pinus sylvestris) and birch (Betula pubescens). The exterior is clad with European larch (Larix decidua), two walls of which have been charred using the Japanese method shou sugi ban. The charring process, in which planks were stood on end around a small brick furnace, helps to inoculate the wood against pests, fungus, and rot.
Finishing the façade and tunnel required experimentation. The students used pine off-cuts—roughly 13 feet long, 3 inches wide, and 3 to 4 millimeters thick—from a local sawmill. But even at that thickness, the wood was too brittle to bend to their specifications. So the students built a long, rectangular bathtub and, using a series of heating elements reclaimed from residential water boilers, submerged each plank into a 140 F bath for a minimum of 15 minutes, softening the wood the way a chef softens lasagna noodles.
After the entry was complete, the wood was finished with linseed oil for weather protection. The walls of the cabin, which is heated only with a wood-burning stove, also contain a vapor barrier, a 6-inch structural wood frame with wood-fiber insulation, and a wood-fiber windproof plate.
Tubakuba is the BSA's first full-scale project built for an external client, the city of Bergen. The cabin, which is free to the public and doubles as a picnic shelter for hikers and a play structure for a nearby kindergarten, aligns with the social mission of the school, which is to focus on projects that would provide social, economic, and ecological benefits to the city. The cabin, which can be reserved through the local parks district, has almost become too popular, Folgerø says. “I think New Year’s Eve is booked until 2020.”