The world’s first doubly-curved cross-laminated timber spiral staircase (to our knowledge), spanning 70′ unsupported throughout its spiral.

We look back on the KF Aerospace Centre for Excellence project. Structural engineers proposed a unique design concept: was it possible to connect the two levels of a museum space with a free-standing spiral CLT stair? This posed significant structural challenges; the spiral shape requires the CLT to both bend and warp, and creates forces in a combination of strong- and weak- axis bending as well as torsion.

The challenge was overcome by using a special application of timber-concrete composite to achieve a stair comprised of doubly curved CLT with a concrete topping throughout the full spiral. Addition of the concrete provides the required mass to control vibrations in the 70ft free span. And creating composite action between the concrete and the CLT significantly increases the overall stiffness of the stair, removing the requirement for any support columns and maintaining a highly aesthetic structure that serves as a welcoming showcase for the KF Centre for Excellence.

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LinkedIn post from StructureCraft