HasleTre, Norway’s first demountable and reusable wooden commercial building, received the country’s prestigious Wooden Building of the Year 2022 award. The building stands as a pioneering model of sustainable architecture, driven by the urgent need to address the climate emergency and shape a resilient future. Oslotre’s design is rooted in environmental consciousness, adaptability, and innovation. HasleTre meets the functional requirements of a modern office building while reducing its greenhouse gas emissions by 60 percent. The building is certified BREEAM NOR Excellent.

A flexible design

HasleTre is located on the outskirts of Oslo’s city centre. The 3,000-square-meter building spans across five floors, including its basement and roof terraces. Oslotre’s directive was to design an ecologically conscious, versatile, and inventive commercial structure that could be easily adapted, disassembled, and reused.

The building is a mass timber structure with a flexible 5x5 meter grid system. This allows for various plans, such as cellular offices, open workspaces, meeting areas, and smaller rooms. The floor system employs a hollow-core floor covering on the top of the cross-laminated timber (CLT) elements, integrating technical installations while facilitating easy disassembly. This system ensures the flexible adaptation of floor plans, thereby extending the building’s adaptive lifespan.

Designed for disassembly and reuse

Hasletre’s design and construction presented a number of challenges, most notably, the need to balance avant-garde construction techniques, materials, and regulatory compliance. Moreover, Oslotre had to secure widespread support for the concept of disassembly and reuse, their approach necessitating thorough communication to highlight the long-term benefits.

A commitment to disassembly required meticulous planning of the building’s components. The primary and secondary construction is designed using large, standardised production formats and dimensions, with as few perforations as possible to the raw elements. This minimises material waste during production, maximising transport volumes and speeding up assembly. Glued laminated timber (glulam) columns and beams are joined with beech dowels, while CLT walls and slabs are fastened using X-fix connectors. This construction system eliminates the need for steel or aluminium joints, significantly reducing steel usage by over 80 percent throughout the entire building.

Materials

HasleTre’s interior predominantly features exposed wood, cork, and wool elements; wooden nails are used as an alternative to metal screws. By harnessing the hygrothermal properties of these organic materials, the building’s energy consumption is reduced and the comfort and well-being of its users are improved. Natural goat hair and wool carpets contribute to the purification of indoor air and a number of windows are operable.

The project makes substantial use of reused and upcycled materials, including ventilation aggregates, acoustic ceiling plates, sanitary installations, and secondary room flooring. In addition, 60 percent of the furniture is upcycled, while 40 percent is made using biodegradable materials or industrial waste, such as ocean-harvested plastics.

HasleTre’s design prioritises a focus on quality, simplicity, and durability in both its structure and interiors. The considered design also facilitates changing spatial needs, technical requirements, and preferences. Notably, the building was constructed at an unprecedented speed, with the entire project completed in nine months in readiness for its new occupant: Save the Children Norway.