A stone’s throw from the department stores, the Palais Garnier has been enthroned since 1875, the heart of the Paris Opera, with its gold and bronze statues, its sculptures, its… scaffolding! It has been standing on the main facade for a few days and hides one of the capital’s architectural jewels from everyone’s eyes. “Restoration is an eternal restart,” breathes Pierre Prunet, chief architect of Historic Monuments, and responsible for the construction site of the southern facade of the Opéra Garnier. And the Paris Opera is like an ocean liner: when you start on one side, it gets old on the other”.
While this emblematic building of Paris is gradually disappearing under a gigantic vertical and metallic labyrinth, soon covered by an “advertising tarpaulin”, which will finance the approximately 7 million euros of restoration and cleaning, 20 minutes wondered about these permanent construction sites which make it possible to preserve the most beautiful buildings of the capital.
“The last restoration of the south facade took place in 1999-2000, recalls Isabelle Morin-Loutrel, curator of historical monuments, in charge of the 9th arrondissement where the Paris Opera is located. But normally, for a facade, the average is more than twenty years between two phases of work. It is not impossible to see a period of 50 years or more, when the stone is not weakened or in a less polluted context”. Is there then a fatality for these old buildings to remain dirty? Or at least more often under construction than exposed to the amazed gaze of tourists and onlookers?
At the Paris City Hall, Karen Taïeb, elected deputy in charge of heritage since 2018, particularly questions lead pollution, mainly due to automobile traffic, and to this particularly toxic element contained in gasoline until the years 2000. “This atmospheric pollution linked to fossil fuels and other combustions has greatly blackened the buildings of the capital, both outside and inside. What has escaped from the exhaust pipes for years has deposited dirt on the buildings, which is gradually cleaned up with the restorations”.
The specificity of the Opéra Garnier
“Be careful, on this specific site of the Paris Opera, it is not just a cleaning”, warns Isabelle Morin-Loutrel. During the 17 months that these immense works must last, the building will also be subject to consolidation, even replacement of its stones. “There is not so much roofing work but the facades are deteriorating a lot with stones that move, which are weakened and generate settlements or flaking”, adds the curator.
For her, the building erected by Charles Garnier, inaugurated in 1875 and classified as a historic monument in 1923, suffers from its original construction, “which cost much more than what was expected”. It partly calls into question the use of materials low-cost during construction, to compensate “for a surge in prices and the lengthening of the work due to a prolonged stoppage due to the war of 1870”. And Isabelle Morin-Loutrel to add: “In comparison, Notre-Dame de Paris has aged really well”.
As Pierre Prunet points out, this large-scale project was decided upon after “a diligent diagnosis because pieces of stone had fallen. The facade was initially secured with nets”. A phenomenon observed particularly in the capital because of the very large number of monuments to be preserved. “The restoration schedule is decided above all on an emergency basis, depending on the state of the structures and not for purely aesthetic reasons,” admits Karen Taïeb.
This work is therefore taking place 23 years after the last facelift of this main facade, a steady pace since its classification but specific to this building, with work in 1931, 1954, 1975, and therefore 2000. “The Opera is probably the building that has the most problems and has the shortest lead times between each restoration,” says Isabelle Morin-Loutrel. This is confirmed by the chief architect of Historic Monuments, who is more philosophical. “We are restoring for as long as possible, but this main facade of the Opera is undoubtedly one of the most complex of 19th century architecture in Paris, by its richness of materials, its decorations and which, moreover, is extremely exposed.
Pollution and incompatibility of stones
Indeed, the main facade of the Opéra Garnier, located at a particularly busy crossroads, surrounded by car lanes, faces the full brunt of the vagaries of the climate. “It is in full wind, oriented due south, southwest. It receives violent sunshine and is exposed to frost, without forgetting that at 30 meters in height, the temperature is not the same as on the ground”, lists Pierre Prunet. Added to this intrinsic pollution in Paris is the aging of the materials used. “As when you cut a tree trunk or extract a forged ore, a stone as soon as it comes out of the quarry, it ages”, explains the architect. Same problem for wood and metal, he adds, adding that regular maintenance can extend the time between each restoration.
Isabelle Morin-Loutrel also specifies that the stones are not all compatible: “like in a fruit basket where some rot on contact with others, the stones age less well if they are attached to others”. An observation also made by Karen Taïeb, who adds: “In the 1950s, we used a lot of concrete. We thought it was the ideal solution to fill the cracks. Aesthetically, it was perfect but it aggravated certain structural problems of these buildings”.
Today, we know better the physico-chemical relationships between the materials, that is to say that we noticed that the facades of the Opera had, for example, been mounted with plaster mortars. They are fragile because the plaster captures the water and dissolves. After Garnier, through restoration campaigns, the joints were redone with cement, and cement and plaster do not work well together. From now on, we restore with compatible mortars to avoid this kind of reaction”, explains Pierre Prunet.
Thus, with the progress of cleaning and restoration techniques, certain previous projects are called into question, even if in the case of the Opéra Garnier, Pierre Prunet tempers. “The restoration of 20 years ago was done in a relatively rigorous way. Notre-Dame-de-Paris, whose restoration by Viollet-le-Duc is contemporary, since it was completed in 1863, also uses plaster to reficher stones. However, there are similar degradations of the facings, a century and a half later”.
Significant progress over the past 20 years
Regarding the cleaning and restoration of these emblematic buildings, the two experts note a clear progress. Pierre Prunet mentions in particular the treatment of lead, already mentioned by the deputy mayor of Paris, in charge of heritage. “Lead on buildings is also a source of risk for the companions and employees who work on these sites,” explains the architect. This preventive approach did not exist today. There will now be a specific treatment that integrates cleaning and decontamination”.
“Before launching a restoration project, several years of study and diagnosis are needed,” explains Karen Taïeb. “I am working on the renovation project for the Fontaine des Innocents, in the 1st arrondissement. The first reflections and preparatory work began at the end of 2018 for a restoration which will begin in July and end a year later just before the Olympics. »
“Having a city with all its own buildings at the same time is impossible”, still slices Karen Taïeb. Moreover, as confided by the curator of historical monuments, Isabelle Morin-Loutrel, “we have always restored buildings in Paris. The historical monuments were born in 1837, first with a single inspector, then a commission, then more substantial services”. To arrive today, to try to preserve as much as possible the existing one and “to transform as little as possible at the time of the restoration”. “And continue to make Paris the most beautiful city in the world for a long time to come,” concludes Karen Taïeb.