After the 2019 fire that damaged Notre-Dame Cathedral in Paris, a leading French company in laser scanning and digitization of historical monuments used building information modeling (BIM) to fulfill an important role in the restoration.
As described in an Autodesk Redshift article in September 2022, Autodesk was a partner in creating a highly detailed digital BIM model of Notre-Dame. The BIM model was then furnished to reconstruction stakeholders and has served a critical role in restoration of the cathedral.
Following are the 5 BIM steps used for heritage preservation of Notre-Dame Cathedral:
1. Data Collection – Billions of measurements were collected onsite using drones and laser scanners. Laser scanning takes distance measurements in every direction to capture the surface shape of building components and objects. A large and thorough set of point cloud data was collected at Notre-Dame by twelve laser scanners producing 46,000 images. The information collection was targeted so it could be used to form a 3D representation of the onsite conditions and structural stability after the fire, down to the individual stones. Notre-Dame has unique features that determined the preferred conditions for the scanning process and the techniques that were used.
2. Analyzing Scans – Supported by cloud computing, the scans were processed, cleaned up, stitched together, and merged to form the best possible 3D representation of the actual site. Information from the new laser surveys was combined with previous scans completed during other projects in 1993 and 2010. Using the “before” and “after” scans, it could be determined what had changed. The Redshift article explained that both 2D and 3D rendering data are considered essential for keeping endangered heritage buildings like 850-year-old Notre-Dame – a product of engineering advances during Medieval times – relevant and dynamic.
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3. 3D Modeling – Creating the BIM model was a fundamental part of the overall project, and it continues to enable simulations, space planning and future management options. Using Autodesk software, seven engineers developed the model using the processed data. Autodesk ReCap Pro was used to prepare the data for import into Autodesk Revit. The BIM model that was then created in Revit contained objects rich with data: floors, columns, walls, windows, roofs. Autodesk explained that, because of the complexity, structural details and size of Notre-Dame, it took over a year to create the full digital BIM model. That model included:
- 12,450 objects
- 323,219 square feet of stone walls
- 42,248 square feet of lead roof
- 186 vaults
4. Documentation – Material types and quantities and technical documents were extracted from the BIM model. These included plans, elevations, sections, shop drawings, perspectives, and orthographic projections. After some debate, it was decided the rebuild would utilize the same types of materials as the original structure: stone, oak wood and lead.
5. Digital Representation – The data-rich BIM model enabled the architects, engineers, graphic designers, stonemasons, restorers, and other construction professionals to get exact measurements for each team’s portion of reconstruction work. The team used and continues to use the BIM model to get accurate estimates of construction costs as well.
Today, four years after the fire, construction efforts are well underway. Hundreds of construction professionals and artisans – perhaps as many as a thousand – are working on Notre-Dame, removing debris, cleaning surfaces, restoring stained glass and sculptures, recreating damaged gargoyles, carving decorative elements, rebuilding walls and ceilings, and reconstructing collapsed vaults.
The plan is to reopen the cathedral to visitors in 2024, the year Paris hosts the Olympics. Final details are expected to continue into 2025.
If you want to explore the ways the BIM process can be a wise use of your company’s time and money, contact GRAITEC Group today. Revit and BIM experts will help you set goals and choose the technology that makes the most sense for your company’s needs.