The restoration of theNotre-Dame de la Paix cathedral in N’Djamena, Chad – which won the Light Steel Frame Building category at the Southern African Institute of Steel Construction (SAISC) Steel Awards 2023 – stands as a lasting monument to resilience and hope. Synergising the building’s history with contemporary design is a significant achievement, and a powerful testament to the tenacity and innovation of South Africa’s steel industry.
SAISC CEO, Amanuel Gebremeskel, makes the following observations about this miraculous achievement: “Through this project, we have demonstrated that our industry can do what others cannot – and, of course, that steel is the best solution. The project team could have used treated timber or even concrete. The fact that they went with a light steel frame structure shows that the local steel sector has moved towards solutions that are better suited to these sorts of projects.”
One of the key aspects of the project brief was that the roof should be constructed using a non-combustible material. That is because the cathedral, originally consecrated by the Catholic church in March 1965, burnt down during civil unrest in 1989.
The once beautiful building waited until 2014 for its restoration to officially begin.
Restoring hope
Local steel company MiTek Industries believed it could achieve what others thought was impossible. The remote location required on-site fabrication, and its Ultra-Span product’s precision cut-to-length capability proved to be the ideal solution. This prefabricated, light gauge steel roof truss system is both lightweight and compact, enabling the weight of the roof to be split across 1100-millimetre centres with trusses clustered close together. This effectively minimises the impact on the original foundations and addresses other key factors such as wind load.
During construction, the 21-metre frames were laid out on a jig adjacent to the cathedral. Two frames were arranged on top of each other with bracing placed between them. Cross-bracing was added to ensure a stable structure so that it could be hoisted into place using a crane that had fortunately been left on site and was available to use.
Once lifted into place onto the concrete ring beam, additional braces were fitted between each pair of trusses, creating a shell structure for the whole cathedral. The curved end at the back of the cathedral was critical, with difficult geometry to overcome.
“The distinctively curved roof design is actually very beautiful, but it is certainly not an easy one to construct. That, of course, speaks to the standard of the architects and the engineers, who were very involved in the process – from start to finish – working closely with the fabrication and installation teams. Together, they explored many different material options, with light gauge steel ultimately chosen as the most appropriate,” Gebremeskel observes.
He points out that working on an existing structure such as the cathedral is always more complicated than working on a new build, because one has to deal with whatever inherent errors are already present.
“The project team did an excellent job. The cladding work was also relatively complicated, as the overall geometry and design of the building is complex. It would be a difficult job to do even here in South Africa – let alone in Chad, close to the Sahara desert,” he explains.
The next challenge was that, with a roof structure clad in light gauge steel tiles, the cathedral’s interior could become very hot in the local climate. A robust insulation solution and underlay were therefore used to keep the building cool.
The restored cathedral is not only aesthetically pleasing, but also serves as a reinvigorated place of worship and community.
Celebrating project management excellence
Gebremeskel notes that the Our Lady of Peace Cathedral not only had a troubled history, but that its restoration was executed under particularly difficult circumstances.
Logistics was the major challenge. The town of N’Djamena is 1000 kilometres away from the nearest port. All the components were shipped via Spain to Cameroon, after which the project team had to contend with extremely poor roads to reach their final destination.
“Chad is not only a landlocked country, but is also a region where there has unfortunately been a lot of conflict for a long time, which meant that getting the materials safety to site was not an easy task. As the parts were premanufactured and only assembled on site, there could be no errors in measurements when it came to the components transported from South Africa. Then, an excellent installation and erection team was also required. This is really about top-notch project management and the logistical capability of our steel sector,” Gebremeskel points out.
Steel is ideal for Africa
MiTek Technical Director Mike Newham points out that in a location such as this, Ultra-Span trusses ensured longevity and durability due to their galvanised coating and resistance to borer, vermin and fungus.
Benefits of the use of steel in this application includedcost-savings on shipping and transportation due to the lightweight nature of the product, streamlined on-site installation and fabrication processes, reduced waste – and the commitment to environmental sustainability by ensuring 100% recyclability of this steel roof at the end of its life.
Further demonstrating that steel is the building material of the future in Africa, MiTek is most proud of how it employed innovative design and technology to address the structural complexities and logistical demands of this project. The company successfully leveraged its Ultra-Span product’s exceptional capabilities to ensure this innovative project excelled beyond conventional parameters – not only locally, but also in the heart of Africa.
A new era for steel across Africa
Gebremeskel believes that the Our Lady of Peace Cathedral project also signals a new era in the use of light steel frame throughout Africa. Whereas there was a time when lower quality steel was used across the continent, the complete opposite now applies.
“What we are now finding is that the more remote and challenging the site, good quality steel is the best solution. The project team could have tried many other materials, but these were just not viable. This proves that steel – and, in this case, light gauge steel – is the ideal solution in environments such as this. We are definitely entering an era when there will be many projects with similar applications for light steel frame across the continent,” he concludes.
