15 Clerkenwell Close is a mixed-use residential and workspace building in London designed by Groupwork and Amin Taha with structural engineering by Webb Yates Engineers. Completed in 2017, the six-storey building reinterprets stone as a primary structural system rather than a conventional external finish. The design uses a load-bearing limestone exoskeleton formed from large pre-cut stone blocks, creating a trabeated post-and-lintel structure inspired by historic masonry construction. The stone columns were individually designed and sized according to the loads they carry, reducing unnecessary material use while retaining the natural character of the stone. The limestone was left largely in its quarried finish, exposing natural bedding planes and fossil markings while reducing additional processing. Behind the stone structure, thermally broken concrete floor slabs span between the columns, with overall stability provided by a reinforced concrete core. The project demonstrates how contemporary engineering can revive traditional stone construction principles, reducing reliance on layered façade systems and positioning natural stone as a durable structural material with long service potential.