When Tradition Meets Innovation: Restoring Notre Dame using Modern Tools
Timber is an excellent and strong construction material, provided its natural characteristics are understood. If it remains wet for prolonged periods, it can suffer from biological degradation, such as wood-rotting fungi. If it is dried too quickly, it can lead to drying defects such as fissuring, and even cell collapse, which will affect its strength in service.. In a project as iconic as the restoration of Notre Dame, attention to every detail is crucial. Even with the world’s best carpenters on site, ensuring the moisture levels of the timber is just as important as the craftsmanship itself. That’s why the Notre Dame project team turned to Tector for reliable, real-time monitoring.
The Timber Dilemma: Navigating Natural Drying Challenges
The restoration of Notre Dame is based on using the same methods as when the church was originally built in 1163. For the wooden framework and trusses in the roof, that means taking freshly cut oak and using it directly to assemble the framework. There has been no drying process before the installation of the oak, which may have been incorporated in modern methods of construction, although it can still be the norm today to use green oak.
Timber becomes stronger as it dries. The minor reshaping that happens for all timber during the drying process aids in the structural integrity of the wooden framework. But only if it dries out as intended. Too quick or too slow a drying out process could have an impact on the cross-sectional dimension, distortion in different forms, and added stresses on connections. Individual timber members will be strength graded prior to installation, which will help minimise these defects in service.
However, this process requires careful monitoring. If the wood dries too quickly or too slowly, it could compromise the integrity of the structure. The challenge lies in tracking the moisture content accurately as the wood naturally dries over time, especially in hard-to-reach areas like the spire, where high temperatures and difficult access make traditional inspection methods ineffective or nearly impossible.
Modern Sensors for Timeless Craftsmanship
The Notre Dame project chose to use Tector’s sensor solution to allow them to continuously monitor the wood moisture content during construction and for many years after.
Tector's solution was chosen for its compact size and ease of installation. Having no wires flying around was important and the ability to have insulated pins to monitor the core wood moisture content in the oak was important to the project.
The sensors were installed around the different joints of the framework to map the full picture of the moisture conditions in, for example, a truss. This provided the project team with accurate, reliable data, essential for ensuring the long-term protection and structural integrity of the framework.
Building Confidence: Real-Time Insights for Lasting Stability
The sensors will provide data about how the moisture content fluctuates across different areas of the roof. It will help the carpenters to understand immediately if any additional support or replacements are needed. By understanding how the different seasons impact the timber and the overall construction, the team can make proactive adjustments, ensuring the stability and longevity of the wooden framework.
The project group is also monitoring the masonry, the support of the arch and the vaults and doing 3d scans. Overall, the project group is doing a great job using the best traditional methods while leveraging modern technology to ensure its durability against both fire and moisture.
Images are taken from Notre Dame’s official flyer.
Acknowledgement
Tector recognises Wigwam as the exclusive distributor of Tector products in France. This collaboration made it possible to implement our solution at Notre Dame, in line with our distribution agreement.
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