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Restoring a Piece of History PUBLIC ACCESS

Modern Materials Recapture the Splendor of a 17th-century French Landmark.

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Mechanical Engineering 121(04), 62-66 (Apr 01, 1999) (5 pages) doi:10.1115/1.1999-APR-5

This article discusses that the French have traditionally maintained the appearance of their historic buildings by using the same materials and techniques used by the artisans who originally constructed them. While this strategy guaranteed the architectural integrity of the structures, it also limited the use of the buildings after their restoration, because historic materials are often unable to withstand the stresses of 20th century use and cannot meet modern building codes. Monuments Historiques reasoned that using modern materials would speed up restoration, adapt a building to modern uses, and still preserve its historic appearance. They demonstrated the feasibility of this marriage of 20th-century materials and 17th-century building styles with the restoration of the Brittany Parliament in Rennes after it had been gutted by fire. Investigators assessing the damage said that 50 percent of the soft stone would have to be replaced, as well as 70 percent of the stone in the building’s southeast pavilion.

In February 1994, a fire tore through the 17th-century Parliament building in Rennes, the capital of the French province of Brittany. The tragedy presented a golden opportunity for officials at Monuments Historiques, the landmarks department" of the French Ministry of Culture, to use advanced materials in traditional architectural decoration to repair the edifice. This represents a shift in French policy for preserving monuments from the ravages of time or accident.

The French have traditionally maintained the appearance of their historic buildings by using the same materials and techniques used by the artisans who originally constructed them. While this strategy guaranteed the architectural integrity of the structures, it also limited the use of the buildings after their restoration, because historic materials are often unable to withstand the stresses of 20th-century us e and cannot meet modern building codes. In addition, repair work is commonly delayed until the specified brick, lumber, or stone can be found in sufficient quantity to begin restoration.

Monuments Historiques reasoned that using modern materials would speedup restoration, adapt a building to modern uses, and still preserve its historic appearance. They demonstrated the feasibility of this marriage of 20th-century materials and 17th-century building styles with the restoration of the Brittany Parliament in Rennes after it had been gutted by fire.

The construction of the Parliament building is intertwined with the history of the region it serves. Rennes is situated at the juncture of the Ile and Vilaine Rivers. The Rance River runs nearby. The construction of the Parliament building was of national importance, because King Henri IV issued a royal order introducing a tax on wine to fund the project in 1609.

Architect Germain Gaultier (1571-1624) constructed canals in the Vilaine River to make it navigable from Rennes to the village of Messac, 30 kilo meters away. This enabled barges to trans-port sinter, a soft stone mined from Loire Valley quarries, most of the way to the construction site.

Gaultier partnered with Thomas Poussin in 1614 in proposing the plans for the new Parliament, but then as now, the mills of bureaucracy ground slowly. Before being approved, the plans were reviewed by Salomon de Brosse, the royal court's architect, who designed the Palais du Luxembourg in Paris. Among the changes the court architect insisted upon were that the Parliament's facade, inspired by Bramante's House of Raphael in Rome, be modified to combine Renaissance and Baroque styles. The first stone of the Parliament was laid on Sept. 15, 1618, and the last on Jan. 11, 1655. The decorative work continued through 1706.

The two firefighters perched atop the ladder at the west facade were among those who battled the blaze at the Brittany Parliament.

The paneled ceiling of the "Room of Lost Steps" was totally consumed, posing a particularly exacting challenge to the architects restoring the Parliament in Rennes.

Grahic Jump LocationThe paneled ceiling of the "Room of Lost Steps" was totally consumed, posing a particularly exacting challenge to the architects restoring the Parliament in Rennes.

The Parliament building was no stranger to fire prior to the 1994 conflagration. On Dec. 29, 1720, a major blaze ravaged Rennes and damaged the Parliament roof. A second fire broke out in the building's west wing in 1836, destroying a portion of the chapel and the paintings in the parliamentary president's offices.

The authorities began repairs in 1838. They rep laced much of the west wing's flooring, installed windows in the galleries, and undertook modifications to eventually build offices in the arched halls on the ground floor. In 1881, J.M. Laloy, architect for the department, or French political region, began refurbishing the Parliament according to its original design. For example, when all the roofing was repaired between 1884 and 1887, he replaced the chimneys, and added gargoyles and a crest in gilded lead.

Over the years, the Brittany Parliament became an integral part of the city's life, most importantly serving as headquarters for the region's appellate court, which also presides over the assize courts.

On Feb. 4, 1994, at 12:29 a.m., someone who spotted flames in the Parliament alerted the Rennes Fire Department. Within a half-hour, 50 firefighters were battling the blaze. By 4 a.m., more than 150 men from neighboring cities, including Saint-Malo, Redon, l'Hermitage, and Montauban, backed by 16 fire engines, finally contained the fire. Many of the firemen remained on duty for a week to fully extinguish burning coals.

The intensity of the blaze quickly depleted the firemen's water reserves and forced them to pump water from the Vilaine River. Ironically, although this extinguished the flames, it further imperiled the building, because the agricultural region uses fertilizers, and the local surface and groundwater are high in nitrates. When the site was closed for two years until initial funding for repair was in place, nitrates in the water let mold form on the soft stone. The mold defaced the stone and weakened it structurally.

Investigators assessing the damage said that 50 percent of the soft stone would have to be replaced, as well as 7O percent of the stone in the building's southeast pavilion.

As had been done in the 19th century, the Ministry of Justice called for the building to be restructured to house the Appeals Court and the Magistrates Court. The only way to accomplish this was to reclaim more space under the roof, while maintaining the edifice's original appearance and proportions. This is when the Monuments Historiques made its major departure from. conventional restoration policy by recreating a historic building with modern materials.

Firemen gingerly remove Nicolas Coupet's painting on wood, titled "France Protects Justice." from the scarred Brittany Parliament following a fire in 1994.

Grahic Jump LocationFiremen gingerly remove Nicolas Coupet's painting on wood, titled "France Protects Justice." from the scarred Brittany Parliament following a fire in 1994.

The first step in bringing the Brittany Parliament out of the ashes was to precisely assess the extent of the damage and the soundness of the remaining structure. Centre Experimental de Recherches et Etudes de Batiment et Travaux Publics, the French building inspection authority, conducted the investigation. To that end, technicians took stone, mortar, and metal samples and analyzed their composition in laboratories.

The agency found that the building's facade sustained damage not only from the fire itself, but from falling rubble and heat-induced buckling of interior metal structures. The metal components date from renovation work performed 100 years earlier, when many of the floors were replaced. Most of the metal was "puddled" iron; that is, pig iron converted into pure iron by heating and agitating it in an oxidizing atmosphere. The buckling of the structures meant that all the flooring on the fourth floor would have to be replaced.

Because it was farther from the fire, the third story took a beating more from falling rubble than from the blaze itself. The building inspectors found that some of the load-bearing walls had become too fragile, and would also have to be replaced. In fact, the building's original structures did not comply with present-day standards for the loads usually borne by modern municipal buildings.

The day after the fire, the building authority chose SETEC Batiment, based in Paris, to rebuild the Brittany Parliament. SETEC was already engaged in renovating a 5,000-cubic-meter edifice in Paris-on the landmark Place Vendome-in collaboration with Alain Charles Perrot, chief architect of the Monuments Historiques. The site in the Place Vendome most recently had housed an IBM office before the building was purchased by a southeast Asian emir, who wanted it restored to its royal appearance during the reigns of Louis XIV and Louis Xv.

SETEC strongly recommended that all the metal floor structures at Rennes be replaced to strengthen the building, and added that the new flooring should be strong enough to support the decorative wooden ceilings depicting Justice and France that were painted by artists including Nicolas Coupet and, it is believed, Charles Errard.

There was also a need to strengthen the existing support structures before a new roof could be installed. Following accepted 17th-century architectural practices, the Brittany Parliament foundation and lower stories were built of hard granite and thick walls (1.7 to 3.2 meters), which gave way to the softer stone and thinner walls of the upper stories. Such a design could not safely support the lateral thrust exerted by a modern roof structure.

In a blend of new and old characteristics of the restoration project, the Aria engineering firm in St. Gregoire developed a system of reinforced concrete supports that are themselves maintained by the third story's freestone, load- bearing walls. The beams of the supports are fixed at one end and are contained in sleeves to a1iow thermal expansion and contraction, similar to a pontoon bridge. Flameproof coatings called Nullifire S. 605 and TS. 615, made by Corroline France, based in Les Mureaux, were applied to the supports. The material will hold up for an hour under exposure to fire, giving firefi ghters that much more time to bring a blaze under control before structural supports suffer serious damage.

A particularly challenging interior repair problem was posed by the Salle des Pas-Perdus, one of the principal public rooms, in the south wing. Literally the "Room of Lost Steps," it served as a waiting room where clients paced before entering the courtrooms. The fire had completely consumed the room's paneled ceiling, which was suspended from the roof structure. The task of repairing the roof and the ceiling was made more difficult because the main roof beams formed a densely interwoven network of wooden cross-pieces that made the roof space inaccessible from below.

In this instance, SETEC turned to Jean Ferignac et Cie, a company that specializes in woodworking and wrought iron fabrication and repair, based in Hautefort in the Perigord region of southwestern France. Ferignac has participated in the restoration of the Grand Theatre of Bordeaux, Waddesdon Manor in Britain, and numerous chateaux and mansions in France.

"We had to reconstruct the vaulting in line with the original design," recalled Andre Perussel, an engineering consultant who superintended the work site. Ferignac installed metal structures to support the ceiling and then attached a secondary metal frame to them. Finally, it attached pieces of laminated wood, measuring 21.1 by 7.1 cm and spaced at 60-cm intervals, to the secondary frame. "Thus, the entire ceiling will be suspended without exerting any strain on the stone cornice on which it appears to rest," explained Perussel.

The woodworkers used metal clamps to attach new oak ceiling panels to the horizontal rails made by the laminated wood. The oak paneling was first coated in Ferignac's workshops with a mixture of quicklime and water to provide a patina giving the appearance of age.

The new flooring would have to be built without the risk of rubble falling to the floors below when the construction umbrella was removed. The umbrella, made of scaffolding covered with corrugated sheet metal plates and translucent paneling, was built after the fire to protect the masonry from additional moisture damage, to aid the draining of the water used to fight the fire, and to protect decorations too delicate to be removed.

The installation of new flooring on the upper floors was complicated because the decorated wooden ceilings were attached to the metal structure of the floors. SETEC decided to keep the wooden ceilings in place while replacement was carried out.

These floors average about 340 millimeters in thickness for spans of 10 meters before they abut another span or meet a bearing wall. They are half as thick as previous floors, which increased volume in the building. The new floors owe their slenderness to a compact collaboration of steel and concrete. The beams are steel filled with concrete, with a steel plate on top, and a concrete slab on top of that.

The original floors consisted of 300- to 400-mm steel I-beams, secondary metal structures with brick arches measuring 140 mm, and wooden board structures consisting of 60 mm rough-plastered joists topped by 25- to 30-mm parquet flooring.

More important than adding space, the new flooring will minimize the outward pressure on the walls because the structure is lighter than the one it replaces.

Using wood for the roof reconstruction was ruled out because of the prohibitive cost of naturally seasoned timber and the lengthy time required to make the repair. Instead, SETEC used a steel design proven in other French public works projects. Steel lattice-girders support the roof where it had to be replaced in three of the Parliament's four wings, and similar steel structures called trellis beams support the new, stronger floors for the service area in the south wing and for office areas in the other two wings.

The last but by no means least significant step in repairing the Parliament at Rennes will be the restoration of the building's paintings, such as Nicolas Coupet's "Justice."

Grahic Jump LocationThe last but by no means least significant step in repairing the Parliament at Rennes will be the restoration of the building's paintings, such as Nicolas Coupet's "Justice."

The lattice-girder is made of steel tubes welded to steel beams to form a lattice, a design that puts ribs where the roof didn't have them before.

Renaudat, a steel construction firm based in Chateau roux, built the lattice-girders and the trellis beams, which altogether comprise 400 metric tons of steel. The company welded the lattice-girders together on-site, and X-rayed the welds before using a crane to lift the beams into place.

The scale of the roof restoration is illustrated by the dimensions of its longest girder, which is used in the south wing. This steel span measures 36.4 meters long and 7.8 meters wide at the base, tapering to 1 meter at the top, and weighs 4S metric tons.

The trellis beams consist of two inclined parts with horizontal, rising chords, and diagonal tension members.

Other details of the roof reconstruction involved installing zenith lighting; that is, natural lighting through a skylight on the roof ridge and glazed roof surfaces in the north wing. The latter is supported by a laminated wood structure supplied by Entreprise Gauthier, a designer of wooden construction materials based in Serent.

The laminated wood is made of 20- to 60-mm-thick boards made primarily of Scandinavian wood. The boards are oven- dried to reach 12 percent humidity, then are glued with a reso rcinol-phenol-formaldehyde solution, and pressed together. They are then treated with fungicide and insecticide. The advantages of the laminated wood boards are that they simplify the fabrication of sectional pieces, eliminate the localized defects of solid wood, dry more quickly than solid wood, and are more cost-effective than solid wood because of their superior yield to wood output.

Final refitting of the Brittany Parliament in Rennes is scheduled for completion this month, although restoration of the interior decorations will continue.

Grahic Jump LocationFinal refitting of the Brittany Parliament in Rennes is scheduled for completion this month, although restoration of the interior decorations will continue.

Gauthier crafted the roof structure of 9.9- by 20-cm laminated wooden joists, spaced 88.9 cm apart and covered with 10.2- by 3.3-cm pine planks. Apertures concealed in the lead flashing, insulated with rock wool, ventilate the structure. Locally quarried slate from Mael-Carhaix was laid in a staggered and graded pattern to impart a classical appearance. Openings also concealed in the flashing permit maintenance workers to reach the roof.

Both the passage of time and the fire of 1994 took a toll on the Parliament's chimneys. These were demolished and then rebuilt on 15-cm-thick blocks containing ventilating ducts. They are coated with stone and brick surfaced to look like the originals. One of the chimneys has been designated to serve as a flue for the heating system.

Work on the metal, wood, and reinforced concrete structures was completed in April 1998, and remaining heavy construction was firushed the following Septemper. The final refitting is scheduled for completion this month. Renovating the decorated rooms will take much longer because of the painstaking restoration of the paintings and paneling. When the work is completed, the Brittany Parliament building will display both the glory of the past and the innovation of the present to tomorrow's citizens.

Copyright © 1999 by ASME
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