Spire's height and historical significance

The spire of the Strasbourg Cathedral, completed in 1439, reaches a height of 142.11 meters and is a prominent feature of the city's skyline. However, its construction was followed by a long and complex restoration effort that spanned nearly two decades.

Restoration project timeline

From 1906 to 1926, workers undertook a major restoration of the north pillar that supports the cathedral’s high tower. This extensive project lasted almost 20 years and was commemorated by the Notre-Dame Foundation on October 9, 2026, marking its centenary.

Trigger for the restoration

The restoration was prompted by a crack discovered in 1902–1903 on the first pillar of the nave, on the north side. This came just after the collapse of the bell tower in Venice in 1902, which raised concerns about the stability of tall structures like Strasbourg's spire.

Structural analysis and findings

In 1907, excavations and analyses revealed a defect of about 20 cm under part of the pillar and largely decayed 11th-century wood. The tower, built between 1399 and 1439, rested on foundations from the 11th century, which were not designed to support such a heavy structure.

Reinforced concrete solution

A reinforced concrete corset with 650 steel bars was constructed around the pillar to support it during the foundation work. This technique, developed by French engineer Hennebique, was used to encase the pillar and allow for the replacement of the medieval foundations with a new concrete base.

Support structures and construction methods

To support the excavation, 12-meter-high reinforced concrete pillars were built around the foundations. The work was carried out in sections, using 8 hydraulic presses to distribute the weight of the tower while the foundations were replaced.

Completion and key figures

The restoration work was completed in June 1925, with the dismantling of the reinforced concrete corset taking place in 1925–1926. Johann Knauth, the original architect, was sidelined before the project's end and died in 1924, two years before the work was officially completed.

Cost and legacy

The entire project cost 3,444,000 old francs, equivalent to approximately 2,450,379 euros today. This expense was spread over 20 years, averaging about 122,000 euros annually. The work was largely invisible to the public, as it took place underground.

Centenary celebration and historical memory

On October 9, 2026, the Notre-Dame Foundation held an exhibition and guided tours in French, German, and English. The cathedral was open for visitors, and the event highlighted the international collaboration that made the restoration possible. Today, a small figure representing Knauth can be seen at the base of the second north pillar, symbolizing his role in the project.