Groupwork Completes High-Rise Supported by Stone Exoskeleton
A groundbreaking architectural innovation reduces carbon footprint.
1Innovative Stone Exoskeleton
Petra Heights, a housing development in north London, features a groundbreaking stone exoskeleton. Designed by Groupwork and engineer Webb Yates, the building uses 1,000 tons of volcanic rock instead of concrete and steel. This innovative approach eliminates the need for a concrete core or steel reinforcement, making it a world-first in architectural design.
2Structural Details
The building consists of three blocks ranging from six to ten storeys. The stone exoskeleton carries the entire weight and wind loads, with no additional support structures. Made from Sicilian basalt and Norwegian larvikite, the frame follows a post-and-lintel construction method, similar to their previous project, 15 Clerkenwell Close.
3Carbon Emission Reduction
The use of stone significantly reduces the building's carbon footprint. Stone is a low-carbon alternative to steel and concrete, which account for 16% of global emissions. Petra Heights' carbon footprint is 32% less than a comparable reinforced-concrete structure, with potential savings up to 75% if a stone-and-timber flooring system had been used.
4Material Challenges
Initially, the team aimed to use local rock to minimize transport emissions. However, they struggled to find UK quarries capable of producing large, strong stone pieces. They eventually sourced Sicilian basalt and Norwegian larvikite, manually split and cut by Italian stonemasons using advanced techniques.
5Design and Aesthetics
Groupwork used a chemical wash to oxidize the stone, giving it a rusty color that blends with the area's historic red-brick homes. This technique, traditionally used in restoration projects, unifies the different volcanic rocks used in the building's construction.
6Construction Techniques
The exoskeleton consists of over 1,000 tons of stone, joined with steel dowels, brackets, and epoxy mortar. The building's mass was reduced by chamfering back the top storeys, optimizing the site's awkward shape. The structure's tallest block reaches 30 meters above ground.
7Future Potential
The stone exoskeleton design could be scaled up to build 30-storey skyscrapers, cutting emissions by 80% compared to steel frames. This project serves as a stepping stone for larger architectural changes, demonstrating the potential of stone as a sustainable building material.
8Architectural Impact
Petra Heights represents a significant advancement in sustainable architecture. By replacing concrete and steel with stone, Groupwork and Webb Yates have set a new standard for low-carbon construction. This project highlights the importance of innovative materials in reducing the environmental impact of buildings.