It's Time for a Stone Construction Renaissance

After writing yet another post about the carbon footprint of concrete, a reader asked why we don't use stone anymore: "Is it time to revert or am I missing some fundamental issue?" The truth is a number of architects and engineers are suggesting that we should use more stone and less concrete. In fact, Parisian architecture firm Barrault Pressacco built a social housing project out of stone recently, noting that it is local and low impact:

"Stone is abundant in France and notably in the vicinity of Paris. Its use is virtuous environmentally and highly contextual, drawing on local resources and engaging the regional economy. Territory, city and architecture are thus brought together by this ancestral material. The energy necessary to extract, cut, and lay stone is limited in comparison to other materials. It undergoes little transformation and its intrinsic properties are conserved in the process. Having been a geological layer, stone becomes a resource, imbued with new purpose and meaning."

Structural engineer Steve Webb of London-based Webb Yates Engineers suggested that stone is the future of construction, even better than wood. He claimed in a recent article that stone "is being replenished all the time through plate tectonics in unimaginable volumes" and "it is inexhaustible, a replenishable natural resource created by geothermal energy. "

"Almost all construction materials are extracted like stone. Timber, one of the few which isn’t, is considered a sustainable material with good reason, but growing it occupies a lot of space with monocultural forests for long periods of time. A tree takes 25 years to grow 1.5m³ of material. If we quarry the stone under the tree we get 500m³ of stone in a month. Although quarrying is highly intrusive and disruptive while it is being carried out, fully exploited quarries can be returned to nature, backfilled with unwanted spoil or reused for other purposes."

Webb noted stone has a significantly lower carbon footprint than the steel and concrete that replaced it in construction.

"The energy required to make cement and steel is used in extraction, processing and transportation. The processing is the fiery business of changing limestone into cement or iron ore into steel. In the case of stone, the energy is only required for extraction and transportation, with no fiery processes at all. Making stone has about half the carbon footprint of concrete and stone is often more than 2½ times stronger; in the case of some dolerites, stone is as strong as steel in compression."

Webb also described how French architects used a lot stone after the Second World War because coal and concrete were in short supply, and developed new technologies to cut it quickly with great accuracy. "The architect Fernand Pouillon pioneered a stone building system on a number of schemes in both southern France and Algeria," wrote Webb. "They are astonishing, modern buildings ennobled by their structural honesty and use of natural materials."

I had never heard of Pouillon and looked him up, finding I had photographed some of his buildings when I was in Marseille, France thinking they were pretty astonishing without knowing their history.

Webb noted stone was historically broken by drilling, wedging, and splitting, and later—as shown by Howard Roark in the Fountainhead—broken with jackhammers. Today, it is cut with computerized diamond saws. Webb sees a future for a lot more of it. "After repeated flooding and other extreme weather events, voters of the future will demand action on carbon," wrote Webb. "Punitive carbon taxes will force up the cost of steel and cement, making them unaffordable." Instead, we will use stone, which "will unleash a new architecture that we can hardly imagine today."

When I first read Webb's article, I thought he might be overstating the case, particularly since I keep promoting minimal use of lightweight materials. It all goes back to the bicycle trip I took across Canada before I entered architecture school, writing in an earlier post that "I have never forgotten that everything weighs something and every ounce matters; in architecture I always tended toward light and portable and minimal."

I have quoted William Braham of the University of Pennsylvania, who wrote in a 2009 article "How Much Does Your Household Weigh?": "The question should be asked about today’s buildings — for environmental reasons, since each additional pound of material requires more energy and resources to manufacture, transport and assemble."

But Webb is not alone in his respect for stone. In 2013, Brent Ehrlich wrote a piece in Building Green—titled "Stone, the Original Green Building Material—where he quoted architects with serious environmental credentials.

“I think we have done a disservice to stone,” says Jason F. McLennan, [then] CEO of the International Living Future Institute. Stone is as elemental a building material as we have, McLennan says. In its simplest form, stone is cut from the Earth, tooled, and installed. That’s it. “There is no ‘perfect’ material, but stone is as close to perfect as we can get,” he said. Many new green materials or products, on the other hand, are manufactured, often using petrochemicals and components transported around the globe. “There are a whole host of issues with these products, and we sometimes overlook products like stone that are staring us in the face.” 

Seeing the big holes in the ground that were once stone quarries, I have always thought that quarrying was equivalent to mining. But it is evidently more benign: It takes 143 pounds of rock to produce a pound of copper.

With quarrying, it is almost pound for pound. As a consultant, Jason F. McLennan toured several quarries run by Cold Spring Granite and concluded, “If you compare them to an even modest forestry operation, the habitat impacts are a fraction of what they are with logging and milling wood.”

McLennan, whose ILF Institute developed the Living Building Challenge, knows his materials. So does Steve Webb. This is all heavy stuff, but perhaps it is time for a stone construction renaissance.