An invisible bond – special bonding technology helped in the construction of the central towers of the Sagrada Família

Throughout a collaboration spanning more than ten years, Henkel has supported the project not only with the Loctite EA 9497 structural adhesive, but also with comprehensive technical support, testing and validation processes tailored to the project’s specific requirements, and ongoing expert collaboration.

A modular construction system sped up the building work

In order to realise Gaudí’s vision – which went far beyond the technical capabilities of his time – a modular construction approach was adopted for the building of the Sagrada Família. This accelerated the process by up to ten times compared with traditional methods.

The bonding expertise of Henkel was crucial in making this solution viable. The technology enabled the stone and steel to function as a single structural element, whilst reducing construction time and maintaining full safety and structural integrity.

The six central towers consist of a total of 826 panels and more than 2,100 stone elements. A total of 24 tonnes of Loctite adhesive was used during construction, averaging around 30 kilograms per panel.

 

The adhesive that bonds the stone and the steel

Behind the towers’ striking appearance lies a technological solution that, whilst invisible from the outside, plays a fundamental role in the building’s stability: the adhesive that bonds the stone and steel elements into a single, strong structural unit. Applied in liquid form, the adhesive moulds perfectly to the joining surfaces, fills in minute irregularities and creates a durable bond between the materials. The bonding process takes approximately 24 hours, during which the panels are kept in a controlled-temperature environment, according to the company’s press release.

You have to prove yourself under extreme conditions

During the development of the Loctite EA 9497, a key priority was a high degree of reliability, as well as the right balance between rigidity and flexibility. This was necessary because the Sagrada Família is exposed to particularly complex environmental conditions. The basilica is situated just 2.5 kilometres from the Mediterranean Sea and is therefore constantly exposed to the corrosive effects of the salty air. Barcelona’s typically high humidity levels, ranging from 65 to 75 per cent, further increase the environmental stress on the structure. Fluctuations between winter temperatures of around 5 degrees Celsius and summer temperatures exceeding 30 degrees Celsius result in cycles of expansion and contraction, whilst the constant vibrations from the two metro lines running close to the basilica also affect the building.

The bonded structure can bear a load equivalent to the weight of up to 100,000 people per square metre. This load-bearing capacity is particularly important in supporting the cross standing atop the Tower of Jesus Christ, which is the highest point of the complex. The cross itself contains no bonded elements; its stability depends on the strength of the supporting structure. The Sagrada Família has now become the world’s tallest religious building: at 172.5 metres, it has overtaken Ulm Minster in Germany.

Modern engineering expertise is helping to bring Gaudí’s legacy to its full potential

The collaboration between the Henkel and the Sagrada Família demonstrates how modern engineering expertise can support the realisation of an architectural vision that began more than 140 years ago. Advanced technological solutions contribute to the realisation of Gaudí’s original vision, whilst preserving the building’s unique character and heritage.
”In the 150th anniversary year of the Henkel, this project serves as a reminder that innovation and collaboration can create value that spans generations” – said Mark Dorn, Executive Vice President of Henkel’s Adhesive Technologies business unit.
Through this business unit, the company is a global leader in the market for adhesives, sealants and coatings.

Construction work that has been ongoing since 1882

Construction of the Sagrada Família, considered an icon of Catalan Modernism, began in 1882 in Barcelona, in an area that was then still outside the city limits. The plans for the church were originally drawn up by Francisco de Paula del Villar in the Neo-Gothic style, but in 1883, Antoni Gaudí, aged just 31, took over the supervision of the work. Gaudí radically transformed the original concept, incorporating organic forms, natural motifs and rich biblical symbolism into the building.
The church, which can accommodate more than ten thousand people and has a Latin cross floor plan, is 90 metres long and 60 metres wide. Its 18 planned towers symbolise the 12 apostles, the four evangelists, the Virgin Mary and Jesus Christ. One of the building’s most distinctive technical and architectural features is the column system inside the church: the pillars, branching out like the limbs of trees, support the vaulted ceiling as if forming a canopy of leaves.

With the installation of the cross in February, it became the world’s tallest Christian church

The final phase of construction of the central towers began in 2016. The Tower of the Virgin Mary was completed in 2021, and the towers dedicated to the four Evangelists were completed in 2023. The final element of the Tower of Jesus Christ – a 17-metre-high, 13.5-metre-wide, four-sided cross made of glass and steel – was installed on 20 February 2026. The cathedral has thus reached its final height of 172.5 metres, making it the tallest building in Barcelona and the tallest Christian church in the world. The completion of the construction project, which has been ongoing for 144 years, was previously planned to coincide with the centenary of Gaudí’s death; however, full completion is not expected until the early 2030s, around the 150th anniversary of the start of the works.