26 CONTEXT 185 : SEPTEMBER 2025 SOKI RHEE-DUVERNE and JIM HART A carbon case for indigenous slate The fact that UK slate can offer clear embodied carbon advantages, primarily due to lower transport emissions, will influence the choice of roofing material for historic buildings. Natural slate has long been the roofing material of choice for many of the UK’s historic buildings, prized for its longevity, weather resistance and continuity with local building traditions. Yet the domestic slate industry has experienced a dramatic decline since the 19th century, with most slate used in the UK today now imported, primarily from Spain. This downturn has been driven by competition from cheaper imports, the closure of local quarries, loss of craft skills, changing construction practices favouring lighter and lower-cost modern alternatives, and regulatory challenges that limit the reopening or expansion of extraction sites. While the idea of conserving historic fabric using traditional materials is well established, the environmental case for those materials has become increasingly important. As awareness grows around the climate impacts of construction, embodied carbon (the emissions associated with extracting, processing, transporting and disposing of building materials) has become a key consideration, particularly in the retrofit and repair of existing buildings. In response, Historic England and Historic Environment Scotland commissioned a study to examine the embodied carbon of roofing slate, with the primary aim of supporting the case for using indigenous slate for repair of historic buildings. The motivation was that if UK slate could be shown to offer environmental as well as heritage benefits, this could strengthen demand and help sustain a struggling but culturally important industry. The study set out to explore how UK slate compared to imported slate and alternatives to indigenous slate in terms of embodied carbon. It looked at both production and transport emissions, and factors such as lifespan, reuse potential and installation practices. Domestic production of slate has declined significantly from 450,000 tonnes in the 1890s to less than a tenth of that in recent years. Today, most roofing slate used in the UK is imported, predominantly from Spain, which accounts for around 70 per cent, followed by Brazil and China. Methodology and data The study adopted a cradle-to-site perspective, covering production (extraction and manufacturing, often referred to as cradle to gate) followed by transport to the site where the slate is ultimately used, but excluded construction, use and end-of-life stages. While a full life-cycle assessment would offer a more complete view, Kirkby quarry, Kirkby-in-Furness, Burlington Stone Limited, Cumbria (Photo: Historic England)
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