“Our planet is partly made of boiling magma and we’re standing on its dry crust,” says London-based architect and stone evangelist Amin Taha. “It’s available almost everywhere and we’re not going to run out of it any time soon.” Strong, fireproof, beautiful, and low in embodied carbon, stone is an ancient building material, used for everything from dolmens to cathedrals. Taha is one of a crew of architects and engineers who are committed to showing its structural potential while embracing modern technology to make it a viable alternative to the carbon hungry products of the industrial era.
Taha chose volcanic rock from Sicily and Norway to build the load-bearing stone exoskeleton of a trio of towers with raked profiles in London. The tallest of these residential structures reaches ten stories. “We’ve used basalt, which has very high heat resistance and compressive strength,” says Taha. “It meant we could use a lot less of the material than if we had used limestone, saving the client money and lowering transport emissions.
On our quarry tour we discovered that the giant slabs coming out of the ground weren’t the homogenous tones and textures you see on the small samples that arrive in your office,” he says. “They have fossils and bands of green and orange in them.” Taha was drawn to the pieces with a rich patina. “We wanted to reveal the spirit of the material in the building’s superstructure,” Taha adds.
Woodstock House, a private home in Belgium, uses materials from within a 30km radius and forgoes concrete altogether. Its structural stone walls are made from sandstone with varied tones ranging from green and grey to ochre and brown. These support the timber decks of this ship-like home that is both low in embodied carbon and deeply in tune with its surroundings, the stone withstanding the swelling waters of the adjacent river.
Stone House in the Indian city of Jaipur is built with the same local salmon-pink sandstone as historic landmarks, such as the 1799 Hawa Mahal in the city. To echo the 18-inch-thick walls of historic structural stone houses but reduce material consumption while creating an effective thermal break, two six-inch walls with a six-inch cavity, bonding them together with gun metal ties for earthquake-resistance were built.
On Spain’s Balearic Islands, the government’s local housing agency has been reviving the tradition of building with a sandstone formed in the Pleistocene by the compression of sea-sand and seashells. This reduces carbon emissions by 60 per cent compared to concrete, while its porosity regulates humidity and temperature, in conjunction with cross-ventilation and Neptune grass insulation.
To accelerate the uptake of stone and simplify construction processes, Amin Taha believes stone bricks are the key. Kiln-fired clay brick production generates some 500 million tons of CO2 emissions across the globe, but stone bricks require minimal processing, and, unlike the ingredients of their clay counterparts, they can all come from the same quarry. Amin Taha estimates that stone bricks produce up to 98 per cent less carbon emissions than fired clay bricks and—when cut from discarded stone, that figure could be even higher. There are practical considerations, too. “You can immediately hand those to a bricklayer—they don’t require specialist training to use,” he says.
The Stone Demonstrator, a three-story prototype, shows off the possibilities of stone bricks and pre-tensioned beams and columns, which still stands on the Earls Court Development Site in London. “We didn’t want to design a spectacle,” says Taha. “It’s a dumbed down library of options that leaves nothing to the imagination.”
But what of the stone spoils of demolished buildings? On a hilltop overlooking Windsor Castle in England, stone and bricks salvaged from the rubble of an 18th-century mansion were used to build a contemporary home called Phoenix House that connects with an existing stone colonnade—the only remnant of the former house still standing. Rough stones with broken edges will be mixed with clean cut pieces. “The stones have seen many life cycles, and we’re interested in finding an architectural language in their reuse,” explains the architect.
When Phoenix House becomes a ruin once more in future centuries, these columns should remain intact, ready for a future reimagining of the country house. The design—which also incorporates timber from storm felled trees on the site—shows how natural materials, contemporary technology, and circular thinking are the cornerstones of decarbonizing the built environment.
You can read the original article at metropolismag.com
The line that jumped out at me was Taha saying you can hand a stone brick straight to a bricklayer because it needs no specialist training. That is true about the brick, and it is the part of the plan that worries me, because the bricklayer is the input that is actually short. We run a job board for traveling trades workers, and masonry is one of the trades where an outfit will fly hands in from three states away rather than wait on the local hall. If stone bricks catch on the way he wants them to, the material stops being the bottleneck and the wall goes up exactly as fast as somebody can lay it. We publish what bricklayers and stone masons are being posted at right now off live job ads, and what it says is that the training question is the easy half.