Putting a Cork in It: In Construction, That Is

Cork isn’t just for bottles. Just look to Marcel Proust, who finished writing À la recherche du temps perdu in his famous cork-lined bedroom.

Insulating, sound-proof, lightweight, good-looking: the bark of the evergreen oak Quercus suber has been used for millennia as a construction material. This hasn’t stopped in the digital age, for cork’s a renewable resource. The bark can be harvested every nine years from a tree that can grow for two hundred years. (The years between harvest allow the bark to rejuvenate to the thickness required for cork stoppers.)

“Cork has very low heat transfer, due to its large air content and small cell size, and high surface friction, resisting movement. It is hydrophobic and rather impermeable to water; relatively inert and surprisingly resilient and resistant to surface wear. It is also elastic and has reasonable compressive strength, with some capacity to take compressive loads.”

So write Oliver Wilton and Matthew Barnett Howland in their survey of the history of cork construction. Thirty-eight hundred years ago on Sardinia, people were already using the bark “as chinking (flexible sealant in the stone walls) and in crumbed form mixed with clay to provide an insulating lining for walls and floors.”

Over the centuries since, Mediterranean cultures have used it for roof coverings, wall making, internal linings (wall, window, and door), and shutter cladding. It’s also been carved for interior and exterior ornamental purposes.

In the nineteenth century, the wine industry supercharged the demand for cork production. The making of cork bottle-stoppers, however, produces a lot of waste. It was this scrap cork, by-product from the stopper industry, that was exploited in the industrialized age. Granulated cork mixed with binders was turned into tiles, bricks, boards, and other products. Mixed with clays, cork made great insulation. In 1863, Englishman Frederick Walton patented linoleum, “a canvas backing sheet coated with a mix of cork flour, minerals, and oxidized linseed oil.” Before being replace by vinyl a century later, linoleum covered floors around the world.

In 1891, another cork product discovered by accident was patented. When cork granules are burned, they don’t break down into heat, smoke, and ash like wood does; they actually expand and solidify. The result is a lightweight, rigid material known as expanded or consolidated cork. Unlike other cork construction products, no chemicals are needed to bind the cork together. Expanded cork made for great insulation, especially in the cold storage industry. Wilton and Howland note that expanded cork is still useful as a “remarkable engineered non-composite biomaterial.”

When the White House interior was reconstructed between 1949 and 1952, cork was used for insulation and sound-proofing purposes. The Armstrong Cork Company advertised its linoleum floors in the 1950s for corporate offices (“Antidote for business tension”) and home (“just right for the bedroom floor”).

Hand-harvested cork, about as traditional a material as could be, was readily adopted by Modernists along with steel, concrete, and glass. Architects including Le Corbusier, Walter Gropius, Alvar Aalto, and Frank Lloyd Wright all incorporated cork into their work. One of the most famous structures of the last century, Wright’s Fallingwater (1937), had its six bathrooms lined with cork. The “floor tiles were hand waxed, to boost their natural water repellence, with the wall tiles left with the natural finish.”

After World War II, the plastics revolution threatened to supplant cork and other biological products. Cork held on, with, for instance, a cork/polyurethane composite used to solve “thermal, acoustic or anti-vibration” issues in construction.

Now, in the twenty-first century, with the shine long since off plastics, cork is resurgent again because it’s plant-based, sustainable, and carbon negative (sequestering more CO₂ than its production emits). A renewed interest in cork also helps “sustain Mediterranean cork oak landscapes, appreciated in the region for their cultural value for centuries and now becoming internationally recognized.”

So what does contemporary cork construction look like? Here’s an entire building made from cork. Here are fourteen other contemporary structures incorporating cork. And, from the Architects Climate Action Network, a presentation on building with cork.

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