Rock of Ages

Might stone be the next frontier of sustainable architecture? Lloyd Alter profiles an ambitious trio — comprising an architect, an engineer and a master mason — that argues the ancient structural material could be better for the environment than mass timber.

Architects have forgotten how to build with stone. Even the titans of the past hundred years — Edwin Lutyens, James Stirling and Norman Foster — didn’t know how to take advantage of it. Lutyens slapped it onto a steel frame (as most North American architects did), Stirling hung it on concrete, and “Foster used sandstone pieces, patiently selected and fabricated off-site, then intricately connected to a structural concrete core,” stonemason Pierre Bidaud says. “A tight embrace of two structural materials leaving a legacy of wasted material and intensive fossil fuel use.” 

For the past century, if architects used stone at all, it was as a veneer. But now, Bidaud, of The Stone Collective, structural engineer Steve Webb of Webb Yates Engineers, and Amin Taha of Groupwork (henceforth referred to as “the collaborative”) are rediscovering stone as a structural material. Joining forces to make stone do impossible tricks, including replacing concrete in buildings, they are also reinventing design practice. 

We must end concrete’s reign as the main structural material of architecture: Almost a kilogram of carbon dioxide is emitted for every kilogram of cement produced, about 60 per cent from the unavoidable chemical process of calcining limestone and 40 per cent from the direct energy use of fossil fuels. A recent study warns the carbon footprint of the construction sector will double by 2050, using up our remaining carbon budget if we are going to keep global heating under 2°C. Keagan Rankin and Shoshanna Saxe of the University of Toronto have concluded that “cities must reduce their construction emissions below 10 per cent of current levels no later than the next two to four decades.” 

The concrete industry is making great strides in reducing its carbon footprint, but Webb questions whether the material is even necessary, pointing out the silliness of mining limestone, grinding it up and cooking it at 1450°C only to mix it with more stone and water to turn it back into…stone. “Not only is it perverse to do this, but the carbon footprint of concrete is 250 per cent higher than stone for a material with only 25 per cent of the strength.” There are other low-carbon building technologies that challenge concrete and steel, such as mass timber, but Webb claims that a post-tensioned stone slab has lower embodied carbon than cross-laminated timber. Webb and Bidaud are pre-tensioning stone, achieving 12-metre spans out of small blocks threaded together with 16 millimetre pre-stressed cables. Stone is stiffer and stronger than concrete on day one of installation, and the slabs can be thinner and lighter. It doesn’t shrink or creep as it dries; it dried millions of years ago. 

Recently, Bidaud, Taha and Webb collaborated on “The New Stone Age: Towards an Ethical Architecture,” an exhibition on view at the Daniels Faculty of Architecture, Landscape and Design in Toronto, which illustrates stunning contemporary stone architecture from around the world while noting that “for millennia, stone has been the most enduring structural material in architecture.” Stone was demoted from load bearing to mere cladding as riveted steel frames allowed buildings to be taller and thinner, aided by wind bracing techniques borrowed from rail bridges. Windows could also be much larger (a big plus before electric light was common and cheap) and foundations could be much smaller. Frame-and-skin architecture took over. The collaborative notes that “within two or three generations, centuries of accumulated expertise largely vanished from practice…Architectural education turned toward concrete design and steel detailing; engineering codes evolved around tensile systems rather than compressive craft.” 

There are many good reasons to rediscover that lost expertise, and to update it with modern technologies and engineering: 

• Stone has up to 96.5 per cent lower upfront or embodied carbon than steel. The collaborative says that combining a self-supporting stone facade with a mass timber floor can yield a 112 per cent reduction (including sequestration, assuming tree regrowth). 
  
  
• Stone rarely ends up in the dump; historically, it has been reused as “spolia.” The Arch of Constantine is made from bits of Trajan’s and Hadrian’s monuments. Stone is among the most easily re-used building materials. 
  
  
• Techniques such as post-tensioning with cables enable the use of smaller stone pieces. Combining stone with mass-timber beams in composite structures enables longer spans. 
  
  
• While the “accumulated expertise” of previous generations has been lost, new technology has stepped up. CNC-driven saws and routers cut stone without much more effort than cutting wood. Non-destructive testing (NDT) machines like ground-penetrating radar and infrared thermography can look inside the stone for flaws and fractures. Sophisticated metal connectors can join stone pieces and provide bracing as required. 
  
  
• Many quarries in the UK are adding equipment to cut stone into standard brick dimensions so that it can be laid up with existing trades. This would be particularly useful in places like Ontario, where much of the stone is fractured. 
  
  
• While many consider quarries unsightly, stone has a surprisingly small geographic footprint. Webb reminds us that concrete is made from quarried limestone and aggregate, and forestry takes up a lot of room. “The volume of rock available to us is infinite in comparison to construction demand,” Webb notes. “If everyone on the planet spontaneously rebuilt their homes in stone construction, it is a volume equivalent to a 40-kilometre-square quarry 20 metres deep — a pinprick in the earth’s crust.” 

Working with stone is not without its challenges. The conventional wisdom is that it is expensive — unsurprising, given that it has mostly been carefully chosen for its appearance rather than its utility. Bidaud says that structural stone doesn’t have to be so pretty: “Using the unselected, unloved stone means the cost can rapidly fall.” Besides, he continues, “stone can now harness the power of the CNC machine to further bring costs down. We now have all efficient machines, from quarrying to installation. Again, adapting new regulations to bio- and geo-sourced material is key. Architects and engineers need to reconnect with the intimacy of stone.” Webb enumerates the three main challenges for architects, trades and authorities interested in exploring stone’s potential as: writing codes of practice, grading stone for safety, and establishing a diversified and reliable supply chain. 

These are universal problems. Unlike wood or steel, there is no established grading system. To satisfy plan examiners and engineering reviews, stone buildings are often overdesigned. Many people simply don’t appreciate the aesthetics of the “unloved” stone that Bidaud embraces: In fact, a local councillor sought to demolish 15 Clerkenwell Close (image top of article), Amin Taha’s own pioneering six-storey building made with raw quarried limestone, because he considered it ugly. And as for the supply chain, quarries should be close to where the stone is used; one study determined that much of the carbon savings are lost if it travels more than 200 kilometres. 

However, most cities are close to sources of stone; for example, much of Toronto was built out of limestone from Queenston, Ontario, on the Niagara Peninsula. The quarry is still in operation, although not in terms of large-scale extraction anymore, and the current owner wants to turn it into a subdivision and golf course. There were other quarries in Georgetown (sandstone), Minden (granite) and Cornwall (limestone). Quebec has more than 20 active quarries producing various kinds of granite. All of these could produce more if there were demand. 

The challenges faced in working with stone today are not dissimilar to those faced by proponents of cross-laminated timber a decade ago. Ten years from now, we might well be into Taha, Webb and Bidaud’s “new stone age.” As they conclude in the exhibition, “Through collaborative work among architects, students, engineers, material scientists, and code authorities, pre-tensioned stone could become a mainstream, low-carbon structural system. In doing so, the construction industry would not only revive one of humanity’s oldest materials but also help us all to build a more sustainable future.”

Triple Dutch

Byborre is betting that its way of making interior textiles — digitally, on-demand and 3D-knitted — can shake up the notoriously water-intensive industry

Everywhere all at once: At the same time we first heard of Byborre, the Amsterdam-based textile innovation studio’s name was popping up in a bevy of interesting collaborations. Its stretchy, strikingly dimensional, double-sided 3D-knitted textiles have lately found applications in new pieces by Hollis+Morris, Stephen Burks and Form Us With Love (our profile subjects on page 64). Yet this is no overnight success: It’s 10 years in the making. In 2015, after discovering they could introduce coloured yarns into mattress ticking machines, co-founders Borre Akkersdijk and Arnoud Haverlag developed software to translate a pixel into a needlepoint. When their product proved too robust for the fast-moving fashion industry, it was time to find another market. 

“This is when I came in,” says Mijke van Ballegooijen, who now serves as CEO of Byborre. “We basically transformed the entire organization and adjusted our business model to fit the interiors industry.” Today, a designer can create a completely bespoke pattern for a hospitality or workplace project, or they can add their signature touch to one of Byborre’s existing cotton, wool or polyester textiles (with or without a fill layer). Generating product on demand for collaborations is part of the company’s bid to make textile manufacturing more sustainable.

To that same end, Byborre has added Sinterama Newlife, made with recycled plastic bottles, to its repertoire; it’s also exploring bio yarns that can yield high scores on Martindale performance tests. All of this is made transparent through the Textile Passport, which outlines everything from the water and energy that’s gone into a textile to the chemical makeup of its dyes. As part of a European Union project, the brand is also testing biomolecular tracing that will allow it to pinpoint the exact source of its wool, down to the farm and the shorn sheep. 

Van Ballegooijen sees Byborre evolving into a fully digitalized textile company so that its knit files can be sent to any mattress ticking factory in the world to fulfill orders. More important, she says, its mission is to replace all conventional textiles with more responsible textiles — by inspiring others to do what it’s doing. “We will have a structural change in the system when all textile companies join us.” — E.P. 

Local Lore

Ever since Formafantasma released the basalt wonders of its De Natura Fossilium collection of 2014, the byproducts of volcanic eruptions — lava, ash, stone — have emerged as readily available natural materials. It goes to show that hyperlocal resources can be fodder for entirely new product explorations. And the next craze might be around regionally specific forms of algae and seaweed, which are the basis of a wonderful paint collection out of Iceland. When was the last time you were excited to watch paint dry? — E.P. 

Recycled lava slab offcuts find new life in SensiEtna, a tile collection by Matteo Thun and Benedetto Fasciana for Florim in a palette that celebrates every stage of volcanic rock formation. Its recycled glass surface comes in three textures: bugnato, crosta and rigatino.

Etna’s not the only Sicilian landmark that spews lava. Alberto and Francesco Meda’s volcanic stone lamps for Foscarini — Alicudi, Filicudi and Panarea — are named after three of the Aeolian Islands. Their delicate forms come in thicknesses of eight to 10 millimetres.

Dýpi, an Icelandic startup, has devised a paint made with mineral-rich calcareous algae, which grows over millions of years in the nation’s fjords. Free of microplastics, it promises a low-carbon alternative to conventional products.