Gaudí left behind an extraordinary architectural project that remained unfinished at the time of his death. Construction was underway on the famous Sagrada Família church in Barcelona, a city in northeastern Spain.
Viewed from a distance, the church appears like a gigantic, living presence on Barcelona’s skyline. As visitors approach it, the structure begins to resemble a living organism. Its remarkable exterior, adorned with intricate carvings, depicts biblical scenes as though they had naturally emerged from the rocks.
From the beginning, the Sagrada Família was designed to continue construction long after Gaudí’s death. However, those who followed in his footsteps faced enormous challenges in completing the project.
During the Spanish Civil War in 1936, Gaudí’s architectural drawings and models were destroyed, leaving his successors with very few construction materials and documents. At one point, there were concerns that the church’s towering structures were too heavy and tall for their foundations and could be damaged by strong winds.
However, nearly a century after Gaudí’s death, the church’s central tower, known as the Tower of Jesus Christ, has been completed at a height of 172.5 metres. The Sagrada Família has consequently become the tallest church in the world.
Inspiration from Ancient Architecture
According to Gaudí’s biographer and art historian Gijs van Hensbergen, the young architect was highly ambitious and deeply committed to Catholicism, with two principal objectives.
His first aim was to present biblical stories in a new way, something that can be seen in the Sagrada Família. His second objective was to overcome the shortcomings of earlier architectural designs.
For this, he turned to an extraordinary architectural masterpiece from the ancient world: the Arch of Ctesiphon, located in the ancient city of Ctesiphon in present-day Iraq.
The structure is an early and prominent example of a catenary arch, an architectural form known for its strength and stability.
Gaudí believed that catenary arches could help him overcome a problem he saw in the construction of churches and cathedrals of his time.
Large Gothic cathedrals relied on external buttresses to support the weight of their vaulted ceilings. These stone structures extended outward from the upper walls and down towards the ground.
Gaudí described these structures as ‘crutches’ for buildings that could not stand on their own.
Instead, he designed the church’s 18 towers around the principles of catenary arches, envisioning structures capable of supporting their own weight.
Van Hensbergen explains that Gaudí was undoubtedly interested in mathematics, but he always viewed it through the lens of divine creation. Gaudí believed that both gravity and catenary arches were creations of nature.
According to Van Hensbergen, Gaudí saw this concept as a central and beautiful theme in his architecture, subtly suggesting that God was the greatest architect of the universe.
As his understanding of building structures and the physical forces acting upon them grew, Gaudí became increasingly confident in his approach. He began removing arches and other structural elements from the church’s design that he believed were unnecessary for maintaining its strength.
Liam Duff, a structural engineer associated with the global engineering firm Arup and a team leader on the Sagrada Família project, says Gaudí changed the design of the church three times.
Gaudí designed tree-like columns for the central section of the church, known as the nave. Inspired by natural structures, the columns branch out towards the ceiling to support the weight of the roof and the towers above.
Standing inside the nave, visitors can see orange and red light filtering through the stained-glass windows on the western side. The tree-like columns create a sense of lightness and weightlessness within the structure.
The Challenge of Heavy Towers
Despite the simplicity and efficiency of the tower designs, a major problem emerged during the construction of one of the tallest towers: its weight was excessive.
The tower dedicated to the Virgin Mary stands 138 metres tall, making it the second-highest tower in the church after the 172.5-metre Tower of Jesus Christ.
During construction, engineers discovered that if traditional stone masonry or reinforced concrete were used, the supporting columns below would not be able to bear the tower’s weight.
One proposed solution was to build a steel framework inside the tower and cover it with relatively thin layers of concrete to reduce the overall load.
In 2014, the Sagrada Família authorities approached structural engineers at British engineering firm Arup for assistance with the project.
Steve McCutcheon, an Arup structural engineer who was involved in the early stages of the project, said the Sagrada Família was an extraordinary building.
He described being part of such a project as something people could only dream of before suddenly being given the opportunity.
Arup’s engineers proposed an ambitious solution to the problem of the tower’s weight.
They recommended abandoning both the steel framework and reinforced concrete. Instead, they proposed using relatively thin layers of stone reinforced with steel cables installed inside them to strengthen the structure through tension and compression.
The approach differed significantly from Gaudí’s original plans.
McCutcheon said the proposal represented a major change. At one point, the engineers even thought the project might no longer require their services and that their involvement had effectively come to a standstill.
However, the situation eventually changed. The principle behind using prestressed stone layers is that stone becomes extremely strong under compression. However, when subjected to tension, it can develop cracks and lose its strength.
When wind strikes a tower and pushes it backwards, the side facing the wind experiences tension. This can cause cracks in the stone structure and potentially damage the tower.
The catenary arch structure uses the tower’s own weight to keep the stone under compression. Prestressed stone layers, reinforced with steel cables, increase this compression and strengthen the structure further.
As a result, even in strong winds, the side of the tower facing the wind experiences very little tension.
Steel cables installed between the upper sections of the tower and its windows also help keep areas under compression where cracks might otherwise develop.
This was particularly important because Gaudí’s design included numerous windows that allowed natural light to reach the lower sections of the church.
The tower dedicated to the Virgin Mary and five other central towers, including the Tower of Jesus Christ, have been constructed using the same prestressed stone technique.
Van Hensbergen believes Gaudí would have been delighted by the possibilities offered by modern technology.
During his lifetime, Gaudí also experimented with different construction techniques for the Tower of Saint Barnabas, located on the church’s Nativity Facade.
He began construction from the bottom using sandstone extracted from Montjuïc mountain near Barcelona.
The stone varies in colour, ranging from light grey and beige to green, yellowish brown, golden, purple and red.
However, Gaudí began using Portland cement in the upper sections of the tower.
Liam Duff says the material was entirely new to Barcelona at the time.
Gaudí’s experiments proved successful. Fernando Villa, head of technology and innovation at the Sagrada Família, says the quality of construction achieved during Gaudí’s time was remarkable.
The Church That Remains Unfinished
Despite celebrations marking the centenary of Gaudí’s death, attended by prominent figures including Pope Leo XIV, the construction of the church remains incomplete.
Among the sections still awaiting completion is the central exterior facade, known as the Glory Facade.
Even after construction is completed, modern technology will continue to play an important role in maintaining the church.
According to Fernando Villa, wind, temperature changes and the gradual movement of the structure over time could cause cracks in the church’s interior and exterior to expand.
In the past, mountaineers were used to inspect cracks and other damage in the Sagrada Família. A complete inspection of the entire building could take two years.
However, drones and artificial intelligence are now being used to identify cracks and other areas requiring maintenance or repair.
Villa says that once the artificial intelligence system has been fully trained, the entire church could be scanned in just one month.
The Sagrada Família is not simply an inanimate monument made of stone. Like a living organism, it responds to the effects of natural elements.
According to Villa, the continuous changes within the building and its dynamic structure reflect Gaudí’s architectural philosophy, which placed nature at the heart of his designs.
