Ireland has had a rich history of stone construction, with some of the most impressive surviving limestone structures in the world, dating as far back as 4000 BC. From the many fine examples of corbelled round towers, to the dry-stone walls of the Aran islands, stone structures in Ireland span from the monumental to the ordinary. Prior to the introduction of cement and concrete, it had been one of the most popular and valued materials to build with. One historian described how in Irish antiquity it was "regarded as the best material of all. In general, all other materials were considered far inferior to stone and lime mortar" [1].

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The status and power stonemasons wielded in Irish society was encapsulated in an old Irish proverb: "Captaen ar an gquarter, nó saor cloiche ar an stáitse", equating to "a captain on the stern, or a stonemason on the scaffolding" [2]. With the introduction of concrete as a cheap and readily-available alternative, structural stone has become less widespread. Today our preference for stone is typically for rainscreen cladding, external paving, or as a luxury feature in building interiors.

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The energy required to process stone for construction is far less than steel and concrete as there is no heating required. Other materials require a significant amount of energy in their extraction, processing and transportation. Cement, for example, uses carbon-intensive clinker, which releases large amounts of CO2 in the kiln-heating process. It has been ascertained that making stone can be about half the carbon footprint of concrete [3]. Furthermore, limestone, sandstone, marble and granite are all readily available in Ireland, there are approximately 209 large commercial quarries operating throughout the country [4]. 15% of these quarries supply large pieces suitable for structural use.

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The Irish government has recognised the need for low-carbon construction materials; Ireland’s Climate Action Plan 2023 aims to decrease embodied carbon in Irish construction materials by a minimum of 30% [5]. The sheer ambition of this goal is staggering when one considers the deadline: 2030, a mere seven years away. For context, currently just 25% of our new buildings in Ireland are built from timber, while most of our construction still elicits carbon-intensive block, steel or concrete [6].

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We need only look to projects like the restoration of Longford’s St Mel’s Cathedral, completed in 2014, to see how we can quarry in large quantities of stone in Ireland today. After devastation from a fire, the restoration this Cathedral is an homage to stone and traditional craftmanship. At least five different species were used in the rebuild, including Bath stone, Carrara marble from Rome, Jura and Dolomite limestone for flooring. The dark-grey limestone that formed the central colonnades was sourced and supplied from a quarry in Co. Carlow, demonstrating the capacity of Irish quarries to provide structural limestone in significant quantities [7].

Stone structures are being explored and used in surprising new ways; the Clerkenwell mixed-use building in London by Groupwork utilises a limestone exoskeleton that supports the building. The coarse limestone columns reduce in size and weight on each upper level, lightening the resultant structural load on the limestone. This solution provides cost-efficiency by shedding the need for a rainscreen cladding, the rough surface limestone performs as cladding and structure all at once. Following this success, Groupwork are now constructing a ten-storey tall residential building with a basalt structure. This would be a notable demonstration of lower-carbon material like basalt as a solution to the challenging technical requirements for medium-rise residential buildings.

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We are seeing a revival in mainland Europe and the UK of the use of stone as an alternative to carbon-intensive steel and concrete. Ireland has the resources to provide structural stone, if clients and architects begin to specify it and collaborate with the supply chain to promote its usage. Projects like St Mel’s Cathedral restoration demonstrate the potential successes of such a collaboration and the opportunity for us to revive the craft of the stonemason into the future.