Imagine a building material that is beautiful, strong, plentiful, durable and fireproof, whose use requires low levels of energy and low emissions of greenhouse gases. It is one of the most ancient known to humanity, the stuff of dolmens and temples and cathedrals and Cotswolds cottages, but also one whose sustainability makes it well-suited to the future. Such a material, according to a growing body of opinion in the world of construction, is among us. It’s called stone.
Last week I sat in the roof garden of a hefty pile of masonry in central London, talking to three advocates of this magnificent substance: engineer Steve Webb, Pierre Bidaud of the Rutland-based Stonemasonry Company and architect Amin Taha. My initial request, driven by a journalistic preference for highlighting individuals, had been to meet Taha alone, but he pointed out that their work is a collaboration of different disciplines. The building on top of which we met is their joint creation: the six-storey, five-year-old Clerkenwell block where Taha has his office and his home.
Their point is that stone has been supplanted in the industrial era by steel, concrete and mass-produced bricks, and is used (if at all) mostly as a thin cosmetic facing, while the hard work of holding up a building is done by the upstart alternatives. They argue that solid stone can once again form the walls and structure of building, with benefits for the environment and for the beauty of architecture. Any form of the material – limestone, sandstone, basalt, granite – can, depending on its properties, be used.
Webb explains how the strength of stone compares well with steel and concrete, yet its environmental impact is far lower. The latter require several different energy-consuming activities, including extraction, smelting, transport, processing and installation. Stone only needs to be cut out from a quarry, taken to a site and put in place. Where the many ingredients of steel and concrete require multiple holes to be dug in the ground, not to mention such things as blast furnaces and rolling mills, the stonework for a given project only needs one.
The planet, as Taha points out, is made mostly of stone. “We are sitting on the cold dry skin of boiling magma,” as he puts it, so we are in no danger of running out. For the same reason, stone should almost always be locally available, which keeps the environmental costs of transport down. The material is long-lasting and recyclable. “Any stone building is a quarry,” says Bidaud. “It can be dismantled.”
At the same time, 21st-century engineering allows stone to be used more effectively than ever before. The material is naturally strong in compression – that is, when loads are pushed down on it – which means it is good for walls, columns and arches, but less so if it is stretched or bent, as in beams or floor slabs. It is now possible to combine stone with a (sparing) use of steel such that it can perform like reinforced concrete.
Webb, Bidaud and Taha are putting their ideas into practice, together and with others. Next year, a 10-storey residential tower is due for completion on Finchley Road in north London (by Taha’s practice Groupwork and Webb’s firm Webb Yates Engineers), whose load-bearing stone structure will make it one of the most remarkable buildings in modern Britain. The three are collaborating on a grand new private house whose masonry vaults look almost medieval in their craftsmanship.
They also cite works by others, such as an eight-storey, all-stone social housing building in Geneva by local architects Atelier Archiplein, and the Salvador Espriu project on the edge of Palma, Mallorca, whose graceful stone ceilings bely the fact that these are affordable homes built by a government housing institute called Ibavi.
These are important examples, as the greatest obstacle to the widespread use of stone is its perceived and actual expense. It’s seen as a luxury item, something for the homes of the one-per-centers. Its use in other countries on relatively low-cost projects shows that it can also be a material for everyday purposes.
Webb, Bidaud and Taha argue that stone doesn’t have to be costly. Taha, for example, has demonstrated that you can cut stone into bricks at the same cost or cheaper than the more usual fired-clay kind, with less than one fortieth of the carbon emissions, which has led to 10 quarries offering them as a commercial product. The problem is rather “forces of habit in the building industry”, where “big beast contractors” have invested in concrete and steel and rely on familiar suppliers of these materials. It “takes time for the whole industry to swivel”, they say.
Meanwhile, architects, contractors and engineers persist in the old ways. Two billion bricks of the traditional, energy-hungry, carbon-intensive kind are bought in this country every year. Steel and concrete remain the standard options for a wide range of building tasks. Webb is scathing about professional inertia on the subject, about architects “who protest about climate emergency, cycle to work and eat locally grown tomatoes” but don’t examine their own decisions about construction techniques.
You can get a glimpse of the highly appealing alternatives in a display at the Design Museum in London, How to Build a Low-Carbon Home, where the work of Taha, Webb and Bidaud is on show (until March 2024) alongside structures in wood and straw. Here, and in the other projects they design and celebrate, they offer a compelling vision of a constructional world that is delightful as well as sustainable.
Who could look at the solid stone structure of, for example, the Mallorcan social housing, where the forces of nature and the work of humans is evident in the fabric, and prefer the processed surfaces and plasticised finishes of their British equivalents? And the great thing about stone is that, having been used for millennia, it’s well tested. It’s conceivable, indeed, that the era of concrete will prove only an interlude in the far longer history of stone. Such a shift won’t happen easily, but it’s an outcome worth striving for.
