The construction

The assembly of the supports began on July 1, 1887 and was completed twenty-two months later.

All the elements were prepared in Eiffel’s factory located at Levallois-Perret on the outskirts of Paris. Each of the 18,000 pieces used to construct the Tower were specifically designed and calculated, traced out to an accuracy of a tenth of a millimetre and then put together forming new pieces around five metres each. A team of constructors, who had worked on the great metal viaduct projects, were responsible for the 150 to 300 workers on site assembling this gigantic erector set.

All the metal pieces of the tower are held together by rivets, a well-refined method of construction at the time the Tower was constructed. First the pieces were assembled in the factory using bolts, later to be replaced one by one with thermally assembled rivets, which contracted during cooling thus ensuring a very tight fit. A team of four men was needed for each rivet assembled: one to heat it up, another to hold it in place, a third to shape the head and a fourth to beat it with a sledgehammer. Only a third of the 2,500,000 rivets used in the construction of the Tower were inserted directly on site.

The uprights rest on concrete foundations installed a few metres below ground-level on top of a layer of compacted gravel. Each corner edge rests on its own supporting block, applying to it a pressure of 3 to 4 kilograms per square centimetre, and each block is joined to the others by walls.

On the Seine side of the construction, the builders used watertight metal caissons and injected compressed air, so that they were able to work below the level of the water.