On 15th April 2019, the world watched in horror as flames engulfed the Notre-Dame Cathedral in Paris. It took just hours for the iconic spire and wooden roof to collapse, changing the face of a building that has shaped the Paris skyline–and French culture–since 1345.

The fire at Notre-Dame was devastating, not only to the French and Roman Catholic communities, but to people around the world. The unmistakable Gothic architecture has made the World Heritage site one of the most recognisable and beloved buildings in history.

With a bittersweet nod, the two famous stone towers and most of the structure survived, and attention quickly shifted to restoring the site – and the public was involved from the very beginning.

Within days over €1 billion had been donated for the building’s reconstruction. Offers of help came from the most unexpected quarters, including the game creator Ubisoft, who offered to share the digital model of Notre Dame created for Assassin’s Creed Unity.

The French government has also reached out to the construction community to support with the creation of a new spire, which Prime Minister Edouard Philippe said should be “adapted to the techniques and the challenges of our era."

This global involvement is reminiscent of how another national and global icon, the Sydney Opera House, was constructed in the 1960s, following a worldwide design competition. The Opera House project showed how an engaging, outward-looking approach to construction can push boundaries, and create a unique and lasting connection between buildings and communities.

The Dream of Ships’ Sails and Mayan Temples

Like Notre-Dame, the Sydney Opera House is one of the most distinctive and admired buildings in the world. It’s perhaps surprising then that the design was one of 233 entries in a 1955 design competition– and was allegedly rescued from a pile of “rejects” during judging.

In retrospect, it’s not surprising that Danish architect Jørn Utzon’s idea was victorious. The building’s sails with their white ceramic tiles gleam over the water of Sydney Harbour, while the huge flights of steps – inspired by ancient Mayan temples – give visitors a sense of arriving in a special and unique location.

The judges at the time were so impressed with Utzon’s vision that his design was chosen despite the fact that no clear plan was in place to construct the building, and the dimensions of key features such as the sails hadn’t even been defined.

Nonetheless, the Australian government pushed for work to begin as quickly as possible, to allay concerns in the public’s opinion. The decision to choose the idea over the practicalities of construction certainly laid the foundations for an icon, but also created incredible hurdles during the build itself.

Given that even to this day, 52% of rework is caused by inaccurate information

Very Familiar Challenges

Following the 1955 contest, construction of the Sydney Opera House began in 1959. Unfortunately, the project ran into major difficulties almost immediately, many of which are very recognisable for construction businesses today. Teams faced unexpected weather, issues diverting stormwater from the site, changes to contracts and ongoing disagreements with the client. Within two years, the project was 47 weeks behind schedule.

But the most significant difficulties came from the design itself – or more specifically, the fact major structural issues hadn’t been resolved before building began. Work on constructing the base of the building, called the “podium,” commenced even before drawings were prepared.

Given that even to this day, 52% of rework is caused by inaccurate information, you can imagine the scale of the problem then that this lack of guidance presented. When work began on the roof, it became clear the podium columns wouldn’t be strong enough to support it– and had to be rebuilt. Designing on the fly definitely came with obstacles, both on site and in public opinion.

Solving the Mystery of the Shells

The biggest hurdle of the entire Opera House project was working out how the iconic sails – or “shells” – could be constructed. The weight and the cost of the materials for the shells was a major barrier; formwork would be hugely expensive, while moulds for the sails would have to be made individually, as each had a unique shape. The issue was so complex that the team went through 12 different iterations of the design.

The team turned to cutting-edge technology to tackle the problem, using a computer system to analyse the forces acting on the shells and to try different alternatives. This was one of the earliest uses of a computer for structural analysis.

The project was in some ways an early forerunner of the technology used in construction now, Building Information Modelling (BIM). Today, builders can even access 3D designs from an iPad on the jobsite, eliminating guesswork and making even complex designs possible. It’s a far cry from those original builders, who didn’t even have paper drawings to work from.

In 1961, using technology and immense creativity, the team arrived at a solution that is now almost as famous as the building itself:

In 1961, using technology and immense creativity, the team arrived at a solution that is now almost as famous as the building itself: to make each shell a section of the same sphere. This way, arches of different lengths could be cast from the same mould, then fitted together. The Sydney Opera House could finally be completed.

Creating a National Icon, Rebuilding Another

The development of the Sydney Opera House was unfortunately wrought with controversy. After so famously winning the design competition ahead of architects from around the world, Utzon eventually left the project due to ongoing disagreements with the government. At the time and even today, public opinion has been split as to who was to blame for his departure.

But that original competition and the story of the building’s construction has forged a lasting connection with the Australian people. The ambitious design and the determination to make it work is now seen as a testament to the national spirit. “It says something about our dare to dream,” said David Claringbold of the Sydney Opera House.

As the French government rebuilds Notre-Dame, drawing on donations and insights from around the world, there’s a hope that this process will provide a similar opportunity to connect the public with the repairs. It’s a chance for the construction community to come closer to people around the world, in saving this global treasure.