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.

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 assembly of the first level was achieved by the use of twelve temporary wooden scaffolds, 30 metres high, and four larger scaffolds of 40 metres each. "Sand boxes" and hydraulic jacks - replaced after use by permanent wedges - allowed the metal girders to be positioned to an accuracy of one millimetre.

On December 7, 1887, the joining of the major girders up to the first level was completed.

The pieces were hauled up by steam cranes, which themselves climbed up the Tower as they went along using the runners to be used for the Tower's lifts.

"A thick cloud of tar and coal smoke seized the throat, and we were deafened by the din of metal screaming beneath the hammer. Over there they were still working on the bolts: workmen with their iron bludgeons, perched on a ledge just a few centimetres wide, took turns at striking the bolts (these in fact were the rivets). One could have taken them for blacksmiths contentedly beating out a rhythm on an anvil in some village forge, except that these smiths were not striking up and down vertically, but horizontally, and as with each blow came a shower of sparks, these black figures, appearing larger than life against the background of the open sky, looked as if they were reaping lightning bolts in the clouds."

The original machines in the West and East piers (up to the first floor only) were provided by the French company Roux Combaluzier Lepape, using hydraulically powered double looped chains and rollers in side guides. Their poor performance led to their removal. They were replaced in 1897 and 1899 by the Fives-Lille machinery, relying on hydraulic accumulators, 16-meter long main pistons, cable loops and manual controls. They were a success, steadfastly lifting the tourists up to the second floor until the late eighties. They were then upgraded to conform to the present day regulations: the old machinery still provides the counterweight power for the dead weights, while the variable parts of the loads were driven by modern high pressure oil pumps and motors controlled by computers.

The original American elevators by Otis in the North and South piers took visitors up to the second floor in a double-decker cabin, using hydraulically powered cables. They were no match for the Fives-Lille units and were scrapped respectively in 1900 from the South pillar and shortly after 1912 from the North pillar, after a failed attempt to re-power it with an electric motor. The increasing amount of visitors during the late fifties led to the installation of large capacity machinery in the North pier in 1965. Manufactured by Schneider Creusot Loire and using the best engineering and electrical machineries available, it was upgraded in 1995 with new cabins and computer controls.

The South pier was rigged anew in 1983 with a small electrically driven elevator by Otis to take customers up to the Jules Verne Restaurant. In 1989, a four-ton service elevator was added (also by Otis) helping to relieve the main elevators of excessive trips up and down.

Built and engineered by Mr Edoux, it consisted of one huge cabin for 110 passengers or a maximum weight of 8 tons and was propped up midway between the second and third levels on the pistons of two vertical hydraulic jacks, 81 metres long. The counterbalancing cabin was latched onto a set of cables linking to the master cabin over the top sheaves. The trip was a seesaw affair during which visitors had to change cabins halfway up by walking along a narrow gangway with a rather impressive vertical downwards view.

The major drawback of this machine was the volume of liquid and proportional antifreeze additives necessary; it was closed to the public every year from November to March. After 93 years of wear and tear, it was replaced in 1982 with two electrically powered sets of two counterbalanced cabins, running all year round.

This also enabled to restructure the criss-cross beams between the second and third floor, allowing for two separate emergency staircases to replace the dangerous winding units that were there from the structure’s origin.