When Napoleon Bonaparte decided to renovate the Basilica of Saint-Denis in order to convert it as a vault for his family, he did not know that it would take more than 60 years to end this work. Three generations of architects will take part into this renovation, each of them having their own ideas for the work to achieve. The basilica wears the different styles of the three architects. The first one to be designated by the Emperor to start this colossal project was Jacques-Guillaume Legrand.
After doing his studies at the Louis-le-Grand school, Jacques-Guillaume Legrand (1743 – 1808) enrolls at the Ecole des Ponts-et-Chaussées. In parallel, he attends some Jacques-François Blondel classes at the Royale Academy of Architecture, where he met Jacques Molinos. Since then, they started to work together. After Blondel’s death, Legrand attends Charles-Louis Clérisseau painting classes who's daughter he married once he came back from Italy in 1789.
Their instructive journey, where they did some complementary research on architecture, had to be shortened and Jacques-Guillaume Legrand came back to France to marry his wife Marie-Joséphine Clérisseau and to take part into architectural works for 20 years.
Still professionaly inseparable, Molinos and Legrand reoganized, constructed and renovated several buildings together, such as the city hall of Auteuil in a shape of the Grec temple in 1792.
The Secretary of the Interior left the renovation of several Parisian monuments to Legrand, while the prefect of the departement named him as chief inspector of the department works. In 1805, he is named to restore the old abbatial of Saint-Denis.
The first and urgent work to do at the abbatial is to repair the adorments and to take off the roof composed of lead. Starting on March 29th 1794, work was completed two weeks after. Because there is not anymore roof, the building cannot welcome any visitors and people started to talk about a possible destruction, to sell it in several pieces or to use it as a store. Around the 29th of October 1794, the transport of the recumbent effigies to the Petits-Augustin warehouse in Paris, headed by Alexandre Lenoir, started.
Guillaume-Jacques Legrand started the building of a new roof made of slate in March 1805.
Around October 1805, Legrand started the renovation of the stained-glass windows which costed a lot of money it terms of materials and employees. Then, he continues with the decoration of the future funerary vault. At this moment, he discovered two hallways in the Carolingian crypt.
After two years of hard working at the Saint-Denis Church and to bring back the tombs of the kings, Legrand decided to settle on the construction site to finish his work.
Because of the amount of work from the different projects that he could not refuse to take, his health sarted to weaken. He died from a severe depression in Saint-Denis, on November 10th in 1808, stopping him to finish his work in the basilica. The architect Jacques Cellérier successed him.