Standfirst: Barcelona’s Sagrada Família is approaching a defining milestone after more than 140 years of construction. A modular building system, steel reinforcement and 24 tonnes of structural adhesive have helped engineers complete the basilica’s tallest tower while preserving Antoni Gaudí’s original vision.
The Sagrada Família has long been one of Europe’s most ambitious architectural projects. Now, advanced construction methods are helping the Barcelona landmark move closer to completion, combining Gaudí’s 19th-century geometric ideas with materials science developed more than a century after his death.
The Sagrada Família reaches a historic height
The completion of the Tower of Jesus Christ has taken the basilica to 172.5 metres. That height makes it the world’s tallest church, surpassing Germany’s Ulm Minster, according to the project’s account.
The milestone is particularly significant because it coincides with the centenary of Gaudí’s death in 1926. The architect devoted the final 12 years of his life entirely to the Sagrada Família, but died before seeing the central towers completed.
Pope Leo XIV recently visited Barcelona to bless the imposing tower. From 2027, the structure is expected to open to visitors, including a walkable viewing platform offering a high vantage point over the Catalan capital.
Gaudí’s religious vision remains central to the design
The basilica is not only an architectural attraction. Gaudí conceived it as a religious story expressed through stone, light and sculpture.
- The 12 towers represent the apostles.
- The floor plan evokes the body of Christ.
- The façades depict episodes from the life of Jesus.
- Coloured light filtering through stained glass creates the impression of a forest inside the church.
Gaudí’s symbolism can be found throughout the building. The Passion Façade includes a representation of the architect, while the crucified Christ is shown with an open book-shaped form in place of a conventional head. The image reflects the idea of the basilica as a “stone catechism” through which visitors can engage with Christian teachings.
The site also contains references to Catalan culture and popular legends, including a depiction of Saint George beneath a structure whose shape suggests a dragon. Guides have additionally highlighted an alleged visual connection between a Roman soldier on the façade and the helmets seen in the Star Wars films.
How modular construction accelerated the work
Building the central towers required engineers to solve a complex structural puzzle. The towers feature hyperbolic forms and must withstand their own weight, wind, seismic forces and the load of the monumental cross above the Tower of Jesus Christ.
Rather than installing individual stones at great height, the project team divided the construction into prefabricated sections. The process involved:
- Preparing modular panels: The towers were divided into 826 panels containing more than 2,100 stone pieces. These sections were pre-assembled at a quarry.
- Joining stone and steel: Engineers used a two-component epoxy adhesive to bond the materials into structural units. Each panel required about 30 kilograms of resin.
- Allowing the adhesive to cure: Panels were kept for 24 hours under controlled temperature conditions, enabling the resin to fill microscopic gaps between the stone and steel.
- Lifting the finished sections: The completed panels were transported to the basilica and installed level by level with millimetre precision.
According to the project team, this approach allowed construction to move up to 10 times faster than conventional techniques. Work completed in roughly eight years could otherwise have taken between 50 and 60 years.
Why the adhesive matters
The adhesive used in the project was developed by German manufacturer Henkel after a decade of research and testing. It was produced at the company’s factory in Montornès del Vallès, near Barcelona.
In total, about 24 tonnes of adhesive have been used in the structure. Its role is not simply to hold pieces together. The resin is designed to accommodate small movements between steel and stone without cracking, an important feature for a tall building exposed to changing conditions.
The basilica faces several long-term engineering challenges:
- Salt-laden air: Its location around 2.5 kilometres from the Mediterranean Sea increases the risk of corrosion in steel components.
- Humidity: Relative humidity levels of approximately 65% to 75% place continuing demands on construction materials.
- Temperature changes: Seasonal temperatures can range from around 5°C in winter to above 30°C in summer, causing materials to expand and contract.
- Urban vibration: Two metro lines run beneath the basilica, creating vibration that must be considered in the structural design.
The project team says the bonded structure can withstand loads equivalent to the weight of approximately 100,000 people per square metre. That capacity is especially important for the cross crowning the central tower.
A 19th-century design completed with 21st-century tools
Gaudí left models and instructions for future architects, fully aware that the project would continue after his death. Since then, successive generations have interpreted and extended his work while using technologies unavailable during his lifetime.
The result is a rare meeting point between historic craftsmanship and modern engineering. Stone carving, stained glass and religious symbolism remain central to the basilica, but digital planning, prefabrication, structural steel and advanced adhesives have transformed how the building can be assembled.
For Barcelona, the latest tower is both a cultural landmark and an engineering achievement. It also demonstrates how historic projects can be completed without relying exclusively on the techniques available when construction first began.
What happens next?
The Sagrada Família is not yet entirely finished. Further work remains on elements including the building’s sculptural and architectural details, while the newly completed central tower is expected to become accessible to the public from 2027.
Gaudí is buried in the basilica’s crypt, close to the project that occupied the final years of his life. He reportedly designed its height with Montjuïc in mind, believing that human construction should not rise above nature.
The latest milestone shows how that principle has been interpreted across generations: the basilica has reached a record height while remaining rooted in Gaudí’s original vision. The key takeaway is that the Sagrada Família’s progress has depended not on replacing its historic design, but on using modern engineering to make that design buildable.
