3D-printed formwork for bespoke concrete stairs: from computational design to digital fabrication

Non-standard stairs have an important role in architecture, but their complex details and three-dimensionality pose significant fabrication challenges. One of the preferred materials for custom stairs is concrete, which can be cast in complex shapes, the only limitation in this case being the fabrication of the necessary formworks. This paper reviews the opportunities and challenges of using 3D-printed formwork for fabricating custom concrete stairs with complex geometries (Fig. 1). 3D printing can unlock an entirely new vocabulary of shapes for concrete structures, previously unavailable with traditional formwork systems. Only a minimal amount of 3D-printed plastic is required to deliver a very thin, stable shell. With these formworks, complex topologies can be achieved in concrete elements. Such elements can optimize the structural performance or improve functional aspects, as well as introduce a radically different aesthetic.