A brand new Hôtel de Région is set to open in France’s sixth largest city, Nantes. The city is the capital of the Pays de la Loire region and is the most important city in the historic province of Brittany.

The vision

In 2011, Nantes will be home to a new breathtaking contemporary-style public building for the regional administration.

The five-story Hôtel de Région combines historical elements with the contemporary. Comprising an arched stone gateway from Nantes’ original 17th century power plant, the building will also incorporate an asymmetrical building shape and a striking curtain wall with stainless steel cladding.

The steel sheets are laser-cut decoratively to resemble various organic forms. Light enters the building through a lacework of stainless steel.

Once completed, the building will be a notable addition to contemporary stainless architecture.

The solution

The steel cladding for the Hôtel de Région is being supplied by Outokumpu. The project is a landmark for Outokumpu and represents the group’s largest project in the architecture, building and construction cluster in France to date.

The skin of Hôtel de Région is supplied by Sofradi, a French company that manufactures metal curtain walls and other specialised items. Because they had little previous experience in stainless steel cladding, Sofradi contacted Outokumpu prior to winning the curtain wall contract.

Sofradi wanted to use Outokumpu because they were familiar with the company name and knew that Outokumpu had a strong local presence in the Nantes region.

One of the Hotel de Region curtain wall panels. Courtesy of Sofradi

The challenges

Sofradi had a number of challenges, which Outokumpu were able to help them to meet.

Ensuring the steel's aesthetic qualities is of utmost importance when creating the stainless steel cladding. To achieve uniform reflection of light, the stainless steel cladding panels must have a highly consistent finish – otherwise the surface will have a blotchy appearance. In order to fulfil this spec, Outokumpu recommended the 4N surface finish, which benefits from superior consistency and will meet the aesthetic needs of Hôtel de Région project.

Equally, the attractiveness of the initial structure needs to be long-lasting. Nantes’ maritime climate increases susceptibility to discoloration, so Sofradi required strong technical assistance to select the right material for the stainless steel cladding.

Finally, the project has exacting service requirements. The construction process means that the stainless steel cladding must be supplied in regular batches, provided with protective plastic coating. Outokumpu has excellent stock and processing capabilities and are thus capable of meeting these challenges.

The results

Outokumpu’s technical experts assisted Sofradi with the properties of various stainless steel grades and surfaces, and introduced to them several choices of grades.

After considering advice on the best stainless steel grade from the building’s architectural firm FORMA6 and Outokumpu, Sofradi decided to use molybdenum-containing austenitic grade 1.4404 (316L).

Sofradi's representative comments on working with Outokumpu: “We felt a warm welcome from Outokumpu and partnership in the way that Outokumpu tackled issues looking for technical solutions.”

Summary

Project
Stainless steel cladding for Hotel de Region, Nantes, France. The 8,000-square-meter, 5-storey building will be completed and handed over by the beginning of 2011.

Curtain wall contractor

Sofradi is an independent French medium-sized company specializing in metal curtain walls, thermal and acoustic insulation, modular sections and aluminum window systems. With 30 years of experience and staff of 140, the company actively develops new products for a wide range of industries including building and construction

Architectural design
FORMA6 of France