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François Coignet’s Reinforced Concrete House

In a quiet suburb, north of Paris, by the River Seine, stands a derelict four-story building. Its windows and doors are broken, some are barred by bricks, and large patches of plaster have fallen off the walls. It is apparent that nobody has lived here for quite sometime. Creepers cover the outer walls, and small branches and shrubs pour out from inside the house through the upper windows. Despite the barbed wire fencing, the property has been vandalized as evident from the graffiti covering the walls. It’s shame that the house is in such a deplorable condition, because this is no ordinary house. It’s a historic monument—the world’s first house built using reinforced concrete.

Maison de François Coignet

Photo credit: Eric Bajart/Wikimedia

Concrete has been around for a long time. The ancient Romans used concrete to build vaulted roofs, arches and great domes. The Pantheon in Rome, built in the 1st century, is the largest un-reinforced concrete dome in the world, and it’s still standing after more than two thousand years. Many Roman structures that survive to this day were built with concrete, or had a concrete foundation. Roman aqueducts and bridges, such as the magnificent Pont du Gard in southern France, have masonry cladding on a concrete core. The iconic Colosseum is largely made of concrete.

After the Roman Empire collapsed, the secret of making good concrete was all but forgotten, until the mid-18th century when the use of concrete returned. Modern breakthrough for concrete came in 1824, when a humble English bricklayer named Joseph Aspdin invented Portland cement.

Cement is the material that binds the aggregate (gravel and sand) together in concrete, and Portland cement was vastly superior than any existing product. Concrete produced by Portland cement is easily workable yet so hard and durable that it could replace even the finest and most prestigious building stone found in the British Isle of Portland—which is why Aspdin called it Portland cement.

Typical concrete mixes have large compressive strength. Build a tall concrete tower and the foundation wouldn’t crack under the weight of all the concrete, brick and stone above. But apply any appreciable tension, such as bending due to strong winds or an earthquake, and the tower will crumble.

Joseph Monier

Joseph Monier

Joseph Monier, a French gardener, was among many who noticed this. At age 23, he began working at the famous Tuileries Gardens in Paris, where he was responsible for the orangery. Joseph Monier used concrete to make large pots for the orange trees, but when moving these pots between the summertime open air and the wintertime greenhouses, the pots cracked and broke. In order to strengthen the concrete containers, he reinforced them with embedded iron meshes. The conventional wisdom of the 19th century held that the iron mesh would expand and contract as the temperature varied and this flexing would crack the concrete sooner. But Monier proved otherwise. Joseph Monier would become one of the biggest promoters of reinforced concrete. He exhibited his invention at the Paris Exposition of 1867, and took out a patent the same year.

François Coignet

François Coignet

Another French inventor, François Coignet, began experimenting with reinforced concrete around the same time Joseph Monier was playing with flower pots. François Coignet was an industrialist who owned a chemical plant in Lyon along with his brother. He moved to Saint-Denis, a neighborhood in Paris in 1851, and opened a cement factory. As a publicity stunt and to promote his cement business, Coignet decided to build a concrete house opposite his factory. This four-story house built in 1853 was the first iron reinforced concrete structure anywhere. The walls of the house was made using prefabricated, reinforced concrete blocks, while the floors were made of timber encased in concrete. The roof was made of iron joist encased in concrete.

Maison de François Coignet

Photo credit: MOSSOT/Wikimedia

Following the success of his first concrete house, Coignet took out a British patent and became a renowned building contractor. One of Coignet’s largest projects was the construction of the 87-mile aqueduct of the Vanne, with arches some of which are over 100 foot high. He also built a sea wall at Saint-Jean-de-Luz, and provided prefabricated concrete elements for the construction of a church at Le Vesinet. This church has a 130-foot spire made of concrete.

The concrete house in Saint-Denis was declared a historical monument in 1998, but it is anything but protected. For years the house was occupied by squatters and was a den of illegal activities. It is estimated that rehabilitating the house would cost 2 million euros.

Maison de François Coignet

Photo credit: lamaisoncoignet.com

Maison de François Coignet

Photo credit: lamaisoncoignet.com

Maison de François Coignet

Photo credit: lamaisoncoignet.com

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