![A broad approach to embodied-carbon reduction drove Stonecutter to the lowest levels so far for the City of London. Courtesy V1. A broad approach to embodied-carbon reduction drove Stonecutter to the lowest levels so far for the City of London. Courtesy V1.](https://corporateresponsibility.thorntontomasetti.com/wp-content/uploads/2024/05/stone-cutter-rev2.jpg)
In February 2024, London’s lowest-embodied-carbon (EC) building topped out in the city’s finance and insurance center. The 350,000-square-foot Stonecutter, a mixed-use office and commercial development, aims for net-zero carbon by cutting EC in several ways.
To avoid the need for temporary works and excavation – and archaeological risk – the new basement lies within the volume of the old one. This approach reused existing piles and sidestepped the need for excavation, but required a lightweight structure. Our long-span design doubles the floor area of the previous building while maintaining the same weight and enlarges the bays by 250%. Avoiding groundworks also accelerated construction, providing significant cost savings while supporting a low-EC approach and circular-economy principles.
To further reduce Stonecutter’s carbon footprint, we decarbonized our structural materials specifications. For example, we replaced 60% of cement with slag in concrete where curing time wouldn’t slow the construction program – 45% of the total used. And for another 9% of the project’s concrete we used at least 50% slag. We selected steel sections produced by electric arc furnace (EAF), which emits about one-third the carbon of blast-furnace production. Altogether, our approach yielded an EC footprint of 550 kgCO2e/m2, which places it in the City of London’s “aspirational” class. The 13-story building is also targeting BREEAM Excellent and WELL Gold standards.