TRÆ High-Rise Building – A Landmark of Timber Innovation and Circular Architecture

Lendager Arkitekter’s pioneering timber high-rise uses upcycled materials, circular construction, and sculptural design to transform Aarhus’ harbor into a sustainable urban landmark.

The TRÆ high-rise stands as a pioneering milestone in contemporary sustainable architecture, celebrated as the world’s first upcycled timber high-rise and Denmark’s tallest timber tower. Rising 78 meters over the evolving harbor district of Aarhus, the building embodies a new architectural paradigm where circular construction, reused materials, and biogenic resources come together to deliver high performance, elegant design, and meaningful social impact.

Emerging within a former industrial zone now undergoing urban regeneration, the project was envisioned as a powerful symbol of ecological and cultural renewal. Its design responds to the site’s rugged character with a material palette that embraces imperfection and celebrates resourcefulness. The goal was ambitious: to prove that large-scale architecture could be built from timber, waste materials, and upcycled components without compromising safety, durability, or economy. This ambition demanded an innovative, collaborative process—one that redefined technical standards and regulatory pathways for timber towers in Denmark.

Navigating the complexities of local codes, fire safety, sea-air exposure, and proximity to industrial zones, the project team conducted full-scale fire tests and experimented with unconventional reused components, such as wind turbine blades adapted into solar-shading elements. This radical approach aligns with the studio’s guiding principle—form follows availability—turning discarded resources into architectural value. The façade reflects this ethos through timber cassettes clad in salvaged aluminum sheets sourced from damaged roofs and post boxes. Their mottled, birch-bark-like texture forms a shimmering surface that shifts with light and weather, transforming irregularity into character.

TRÆ is defined by its three softly sculpted volumes—referencing the Danish word’s triple meaning: tree, timber, and three. These rounded forms optimize daylight, reduce wind pressure, and create an elegant presence on the waterfront. A sinuous pedestrian bridge connects the building directly to the city’s new highline, enhancing public accessibility and weaving the development into the fabric of Aarhus. At ground level, social programming enriches the neighborhood, including a restaurant operating as a community initiative and partnerships that support vulnerable groups through maintenance work and meal distribution.

Structurally, the tower relies on glulam columns and CLT slabs paired with low-carbon concrete cores to ensure robustness and fire resilience. Nearly every visible surface incorporates reused, biobased, or upcycled materials—from reclaimed timber floors and aluminum cladding to acoustic panels made from PET felt, waste textiles, and repurposed windows. Mature trees relocated to the site reinforce the concept of a living, urban forest at the tower’s base. User studies conducted after occupancy reveal strong connections between the natural textures, abundant daylight, and the perception of healthier, more inspiring workplaces. Many highlight the calm, tactile atmosphere created by biogenic and reused materials, seeing the building as both a sustainable solution and an innovative environment that sparks pride and forward-thinking.

Life Cycle Assessment results confirm the building’s impact: a 30–50% reduction in embodied carbon compared to a conventional concrete high-rise. Its three “Living Lab” levels serve as ongoing research platforms exploring upcycled materials, circular construction strategies, and future-ready workplace concepts. By integrating environmental responsibility, technical innovation, and social value, TRÆ sets a new benchmark for high-rise sustainability.

All photographs are works of Rasmus Hjortshøj