As we've previously reported, The Stone Collective is a cross-industry initiative bringing together quarry operators, stonemasons, architects and engineers to advance the use of structural stone in contemporary construction. 

Last year, the Collective launched what has now become a book series to share practical knowledge, research and real-world case studies that aim to help accelerate the wider adoption of structural stone, providing the industry with a common reference point grounded in collaboration across the supply chain. The first volume was produced in collaboration with Albion Stone, Hutton Stone, Lundhs, Polycor, Paye Stonework & Restoration and The Stonemasonry Company. For the second volume, the team has evolved to include Johnston Quarry Group alongside returning collaborators Hutton Stone, Lundhs, Paye Stonework & Restoration and The Stonemasonry Company. 

With the next installment set to be released on Thursday, we thought we’d whet the appetite with a standout essay from the first volume titled ‘Spoila’. Watch this space for more insights from the new publication!

Spolia: Repurposing Masonry

Spolia (from the Latin: 'spoils'; singular: spolium) is the name given to stone taken from an old structure and repurposed for new construction or decorative purposes. It results from an ancient and widespread practice whereby stone that has been quarried, cut, and used in a built structure is carried away to be used elsewhere. This is an early example of what is now referred to as the circular economy.

Image Credit: Robert Greer

More than half of the total material used to construct a building is attributed to the main structure and envelope. Reusing components from existing, soon-to-be-demolished, or already deconstructed structures significantly reduces the need for manufacturing new components, in turn reducing the carbon cost of the building.

As we start to see the financial cost of carving new stone usurped by the carbon cost associated with its creation, the dismantling and repurposing of stone façades is becoming more common. The technology available to support the process of repurposing masonry has leapt forward, allowing us to provide a greater level of technical certainty.

The development of Light Detection and Ranging (LiDAR) and Ground-Penetrating Radar (GPR) survey accuracy allows for the overall volume of stone within a building to be determined. The existing building acts as a stone quarry, removing the expectation of building with new stone for all repurposing projects. However, an early understanding of the original construction is necessary for such a scheme to be successful.

Image Credit: Robert Greer

The comparable commercial benefit of repurposed stone rather than new stone is bolstered when considering the substantial reduction in carbon emissions, the improved thermal performance of the external fabric, and the elimination of inherent steel frame corrosion risk defects. An optimization strategy undertaken with GPR scanning makes it possible to calculate the external stone thickness of masonry façades, enabling all stones to be thinned down to a consistent depth. Reducing wall thickness provides space for thermal improvements such as cavity construction and insulation or an increase in net lettable area.

When reusing components from a building that have been exposed to weathering, they must be evaluated for suitability. In repurposing projects, the first survey confirms the performance of the stone, and a suite of tests will provide an assessment of the long-term durability and performance in line with current expected test standards.

A coordinated strategy for deconstruction needs to be planned jointly by the demolition contractor and the masonry specialist. This ensures that the timing of each step aligns and that the strategy for removing masonry can be synchronized with the demolition requirements, including the lifting and logistical aspects.

It is widely understood that products should be used for as long as they remain functional and reused or repurposed to the greatest extent possible when they reach the end of their service life. Masonry is designed to be durable and long-lasting and can be removed when a building is renovated or demolished, allowing for repurposing. Spolia is a key component in recognizing the importance and value of reclaiming materials to challenge waste and create a robust and climate-conscious circular economy.