A first-of-its-kind hybrid cross-laminated timber system—combining mass timber with natural fibres—is the basis of a new building that promises to use 33% less wood than a traditional timber system.
Known as the Hybrid Flax Pavilion, the wave-like roof is the work of the University of Stuttgart’s Institute of Computational Design (ICD) and Institute of Building Structures and Structural Design (ITKE), combining 24 cross-laminated ‘pure’ timber panels with 20 hybrid panels made from timber and flax fibre.
“The goal of this novel hybrid building system is to achieve expansive column-free space while minimising material usage, thus leveraging the synergy between wood and natural fibre composites,” said Jan Knippers, the head of Stuttgart’s ITKE. In effect, “incorporating flax fibre components to reinforce the thin wooden elements facilitates the use of fast-growing resources for the construction industry.”
Stuttgart is at the forefront of research into new materials and construction methods, with Professor Knippers stressing that the future of timber construction lies in “an integrative approach to scientific research, computational design, digital fabrication, and expert craftsmanship.”
Hemp, jute coco and sisal can also be combined with timber
Wood Central understands that the use of the new fibre panels made it possible to reduce the thickness of CLT panels from 320mm to 120mm (which resulted in one-third less timber in the building system) thanks to a fibre ‘cage’ screwed into the underside of each hybrid timber panel.
And it’s not just flax either; Professor Knippers is confident that different types of natural fibre materials could be used in place of flax:
Here we use flax fibres, a plant that is cultivated in central Europe, but in other parts of the world, it could be hemp, jute, coco, sisal or others.
While the fibre ‘cages’ handle the tension loads, timber manages compression forces and creates a surface for a roof enclosure. “This results in a hybrid system with the strength and stiffness required to support high snow loads encountered in the foothills of the Alps.”
Wood Central understands that multiple layers of flax are reinforced in the panels, with a primary ‘spine’ layer aligned with the main beam direction; a ‘fan’ layer gradually disperses loads to the edge and visually dominant ‘lattice’ layers, creating uniform fibre mesh. In addition, two corner layers boost reinforcement in structurally critical areas.
A 5-axis robot milled the panels, which included chamfered edges that continuously changed angles to match the varying orientations of the fibre connections and holes for facade connections – tapping into academic research and industry know-how to design and manufacture the new system and construct the new building in just 12-months.
“Onsite assembly of the roof elements took just eight days,” Professor Knippers said, adding that the flax fibre was wound with the help of a 6-axis robotic arm, fully equipped with a custom end effector.
World’s First Curved, Wind-Proof CLT Tower Rises in 3 Days
Professor Knippers’s team was behind the nearby Wangen Tower – the world’s first multi-storey structure made from recycled concrete, steel, and self-shaped cross-laminated timber.
Covered by Wood Central in May, the 23-metre-high tower uses large panels of self-shaping cross-laminated timber. Self-shaping timber is created by calculating how timber shrinks and warps as it loses moisture and then drying it in a humidity-controlled chamber—a method that allows the tower’s twisted form to be created from just 12 thin wooden panels without heavy machinery.
