The Long Reach: Carbon Balance

A collaboration between Groupwork, Webb Yates, and The Stonemasonry Company, the installation takes the form of a 9-metre-high post-tensioned stone frame, supported and braced by three unprocessed timber posts. A 6.5-metre cantilever projects across the plaza, counterbalanced by a large, roughly hewn boulder that makes the forces acting on the structure visible. From the raw boulder to the precisely cut structural elements, the composition demonstrates how stone can be used in different forms with relatively little processing. Different stone types are deployed according to their structural demands, including high-strength Belgian Blue stone in highly stressed elements and Pierre de Bretigny limestone in less heavily stressed areas.

The structural design exploits stone’s high compressive strength while using post-tensioning to address its relatively low tensile capacity. High-strength steel tendons pass through the individual stone elements and are tensioned to compress them together, forming beams and columns capable of resisting bending and transferring loads through the frame. This enables longer spans and more complex arrangements than would typically be possible with traditional masonry construction, while straightforward connections allow the frame to be assembled and disassembled using relatively simple construction methods.

Stone works primarily in compression, while the timber bracing is used in tension, drawing on principles found in traditional timber-and-stone construction. The two materials are combined according to their structural properties, testing how lightly processed natural resources can be used efficiently within a contemporary structural frame. Timber stores approximately 1,000 kgCO₂ per cubic metre, while the quarrying and cutting of the stone produces around 36 kgCO₂, creating the potential for a structural system in which the carbon stored within the timber exceeds the emissions associated with producing the stone.

The project is the latest development in more than a decade of collaboration between the three practices and other specialist partners, exploring the structural potential of stone and its role as a low-carbon building material for the 21st century.

The installation, on display from autumn 2026 until spring 2027, was realised with financial and in-kind support from PICCO Engineering, with construction undertaken by Darteck Construction Group.