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A new icon in Paris

6 min
An Exceptional Building
An exceptional building erected by Bouygues Construction in a design-build project was inaugurated on 19 October, 2016, in Paris. It is a blend of tradition and modernity.
Dressed in a black cassock, with a gilt cross hanging from his neck, Father Maxime Politov pauses before the door of Cathédrale de la Sainte-Trinité in Paris. “The church is oriented east-west. It faces east and the rising sun, the symbol of the risen Christ,” says the vicar general of the Diocese of Chersonese1 with a trace of a Slavic accent.

Located in the heart of the seventh arrondissement, the complex of religious buildings is designed as a neighbourhood in itself. In addition to the church, it comprises a cultural centre, a parish centre, and a school, with an alley running through it between Quai Branly and Avenue Rapp. The 4,240-m², on which the offices of the French weather bureau formerly stood, was purchased by the Russian Federation from the French state in 2010 for €73 million.
This project is the most
exceptional of my career.
Jérome Ansaldi
Director of Production at Bouygues Bâtiment Ile-de-France Construction Privée.

The neighbourhood is rather exceptional, with security a crucial issue that had to be taken into account. Adjacent to the site is Palais de l’Alma, which, in addition to postal administration offices, houses apartments occupied by members of the French president’s staff. After two years of construction work, some hurdles in obtaining the final building permit, and numerous trips back and forth between Paris and Moscow, everyone felt the same joy of having taken part in an adventure that was historic both technically and from a human standpoint.
« The religious and cultural dimensions of this project are immense. It is the most exceptional of my career,” says Jérôme Ansaldi, Director of Production at Bouygues Bâtiment Ile-de-France Construction Privée. “And the fact that it was totally paid for the day it was accepted shows the solid relationship of trust we forged with the customer.”
Goodbye to the traditional wood-frame roof covered with hammered copper and gold. The cathedral’s domes, so typical of Russian Orthodox architecture in shape, are totally twenty-first century in their construction. The architect Jean-Michel Wilmotte wanted them to be smooth, with no visible joints. “We had the idea of calling on Multiplast, a company based in Vannes that builds boat hulls out of composite materials,” recalls Ghislain Martineau, a Deputy Head of Works at Bouygues Bâtiment Ile-de-France Construction Privée and also its representative in the design/build consortium. Although Multiplast’s only experience in building construction was making small, fake domes for Disneyland Paris, it rose to the challenge.

Each “bulb” consists of several “petals” made by pouring fibreglass and epoxy resin into special moulds, with a cone at the top to support a cross. The largest dome measures 11.5 meters in height, and the four smaller ones six meters. As for their colour, Paris City Hall asked that they not be too bright. Wilmotte therefore came up with a gold and palladium alloy that has a dull lustre. The colour, called “moon gold,” varies in tone depending on the light striking it. Some 90,000 extremely thin (0.35 microns) sheets of gold leaf measuring eight by eight centimetres – and, amazingly, weighing a total of just just two and a half kilos of gold– were applied by hand.
Did you know ?
A semi-circular auditorium with 209 seats (including ten for people with reduced mobility) is located on the ground floor of the parish centre. It will serve as a venue for conferences, concerts, film showings and other such events. The structure of the auditorium is suspended – a true technical feat.

To ensure excellent acoustics, the interior walls are lined with micro-perforated wood panels, and the seats are upholstered with fabric The control room is separated from the auditorium by a wall of ultra-resistant Dacryl.
“The domes were made from a composite material, using a completely new process that offered multiple advantages,”, notes Etienne Dumas, Works director at Bouygues Bâtiment Ile-de-France Construction Privée. These included the ability to precisely follow the architectural plans and to make the domes considerably lighter (the largest weighs just eight tonnes, compared with forty-two tonnes if it had been built with traditional materials). It also meant the gilding could be done in the workshops of the company supplying the gilding, Atelier Gohard, rather than on site, as is usually the case. The gilder was thus protected from inclement weather, which can have a serious impact on the work schedule. A cross stands atop each of the five domes, which symbolize Christ and the four Evangelists. They too were gilded in France, though they were made in Russia, as were the ten bells, which hang in the cultural centre building, and which, in accordance with Orthodox tradition, have no name and...are not tuned.
« Take your time, you are building for eternity. » These words spoken by Monsignor Nestor, Bishop of Chersonese, to the teams from Bouygues Bâtiment Ile-de-France, cast a revealing light on the architectural methods and choice of materials. The glass and white stone façades of the Cultural and Spiritual Center buildings glow in the autumn sunlight. To obtain this surface of alternating materials, no fewer than 12,000 modules with varying profiles were made, including 72 unique ones for the cathedral and 25 for the three other buildings.

“Each layer of stone in the church has a specific profile,” explains Thomas Rousseau, a Head of Works at Bouygues Bâtiment Ile- de-France Construction Privée. “That required making 72 different stone courses. Each stone, which is unique, was cut and then wrapped up in a precise order. This large-scale construction process was rigorously organized. We had to create as many grinders as there were profiles of stone.”

About fifteen workers spent ten months cutting the 1,600 m3 of white Massangis stone quarried in the Burgundy region. Another unique characteristic of the church façade: at every fourth or fifth row of stone, an angle was formed with a bent glass sheet and covered with gold leaf. This difficult task was performed by an artisan glassblower at the Emmanuel Barrois workshops.
Large dome
8.2 tonnes; 11.5 metres
3.3 metres
Small Domes
2 tonnes; 6.11 metres
2.3 metres
90 000
sheets of gold leaf weighing 2 kilos
1,600 m³
of Massangis stone from Burgundy

Inside, the cathedral’s walls are still a stark white rather than covered with ornate Orthodox decoration. It will be another two or three years before the frescos that will adorn them can be admired. However, this art, which contains natural pigments like those used in the fourteenth century, cannot be painted on smooth surfaces. The 17-meter-high walls, which were built with a single pour of concrete (a real feat), had to be covered with brick. Then specially trained French workers applied between nine and thirteen coats of a traditional Russian plaster on the brick to obtain an irregular surface that would add relief to the future frescos and render them livelier.

On December 4, with incense filling the air, Kirill the First, Patriarch of Moscow, consecrated the cathedral. Five new golden flames now glow in the Paris sky.

1. The Diocese of Korsun serves the parishes of the Moscow Patriarchate in France, Spain, Switzerland, and Portugal.
Alternating layers of white Massangis stone
and glass on the façades
of the Russian Spiritual and Cultural Center.
The « moon gold » color of the domes was obtained
by forming an alloy of gold and palladium.
The interior of the cathedral.
Within two or three years, the walls
will be covered with frescoes.
The interior of the cathedral.