In February 1854, the worksite restarted. An entrepreneur from Argenteuil, Pierre François Joly, one of the pioneers in metal construction, was associated with the structural and load calculations for the assembly. He also supplied the iron components. The cast iron components, particularly the immense columns 10 metres high, were cast in the foundry at Mazières, near Bourges, as well as in the Muel, Whal et Cie establishments in the Meuse, before being brought to Paris.
The weight of the materials used was considerable: for just the eastern sector, no less than 1,500 tonnes of cast iron and metal were used. The first work was performed quickly: the first two buildings were inaugurated in October 1857 and the entire eastern sector (representing six buildings) was completed a year later. Four other buildings were erected more slowly, between 1858 and 1874. The complex was only completed in the period between the wars, with the construction of the last two, those surrounding the wheat market.
In his Monograph on the central covered markets of Paris (1863), Baltard mentioned "the pronounced enthusiasm for buildings in metal [dominating] the public taste", which explained the immense popular success of the central markets. Furthermore, Baltard's construction was an entirely innovative metal structure: the exterior envelope of the buildings was composed of a metal frame based on a sub-structure made of brick and a base of brown Vosges stone, giving an unprecedented decorative effect.
To avoid the use of tie-bolts that he considered unreliable and unsightly, Baltard made the structure rigid with large triangular metal brackets. A fine designer, concerned with ornamental questions, he gave them an elegant decor. Professional magazines and major newspapers of the period, such as L'Illustration and L'Univers illustré, all mentioned the wonder aroused by the aesthetic qualities of this metal structure, amplified by the light diffused by the huge lateral bays.