Aerial view of the Eiffel Tower

How long can the Tower last?

Wednesday 7 August 2019

Modified the 14/08/19

The Eiffel Tower is so much a part of the Parisian landscape that it would be hard to imagine Paris without it. But will it last forever? By Bertrand Lemoine.

The oldest constructions of humanity such as the Egyptian pyramids have existed for just slightly over 4,000 years. But the iron that the Eiffel Tower is completely made of is different from the stone of the pyramids. The enemy of iron is corrosion, caused by water and air that gradually oxidize iron exposed to open air. The layer of paint that protects the metal of the Tower is very effective, but it must be periodically replaced. In fact, the Tower has been repainted for over 130 years, about once every 7 years. So if it is repainted, the Eiffel Tower can last... forever. 

Micro movements due to the sun and wind

Another phenomenon that can weaken the Tower in the very long term is its micro movements. The wind also makes it slightly vibrate, and the sun causes the sections exposed to its rays to expand. During its daytime course, the sun successively heats the eastern, southern, and western sides of the Eiffel Tower, whose sides alternately expand due to the heat. During the nighttime, they return to their initial state. Due to this expansion, over a 24-hour period, the top of the tower thus traces a roughly circular curve with a diameter of approximately 6 inches (15 centimeters). 

These small movements lead to metal fatigue that weakens the structure in the long run. This is similar to folding an iron wire over and over, which ultimately winds up breaking. We could thus imagine that it would take about a thousand years for take the Tower down. But in the meantime, perhaps all of the components of the Tower will be replaced one by one, without affecting its shape or distorting its details. So long live the Eiffel Tower!
 

The full importance of painting the Tower should be realized, it is the essential element in the conservation of metal works and the more meticulous the paint job, the longer the Tower shall endure.
Gustave Eiffel

Bertrand Lemoine is an architect, engineer and historian. He was a research director at the CNRS and general manager of the Atelier International du Grand Paris. He is an internationally recognized specialist in the history and current events of architecture, construction, the city and heritage in the 19th and 20th centuries, particularly in Paris, Greater Paris and the Eiffel Tower. He is the author of forty-three books and several hundred articles on these subjects. He is currently a consultant on architectural, urban, digital and energy issues.

Photo Bertrand Lemoine

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