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Existing building modelling is the creation of a precise digital 3D model of an existing building. Measurement data, such as point clouds from 3D laser scans, is converted into a semantic model for planning, refurbishment and operation – including real deviations from outdated plans.
Why is existing building modelling important?
- Reliable data basis: An up-to-date representation of the actual building condition and reliable existing building data help reduce planning errors, change orders and additional site visits.
- Faster decisions: Structured geometry and attributes accelerate coordination for refurbishment, renovation and MEP planning.
How is an existing building model created?
- Capture the building
- Generate a point cloud
- Model building components
- Add attributes
- Check quality
- Export the model
What are the results of existing building modelling?
- 3D CAD models
- BIM-ready building models
- Floor plans
- Sections
- Elevations
- Room books
Types and levels of detail
- LOD/LOI: Level of Detail and Level of Information define how detailed the model and its information should be, depending on the intended use – from a simplified envelope model to a detailed component catalogue.
- Deformation-accurate model: A model that represents deviations and irregularities, such as uneven walls, especially in existing buildings.
- Discipline-specific modelling: Architectural, MEP and structural models can be created separately or integrated into one coordinated model.
Common mistakes and misunderstandings
- “If the model looks good, it is good”: Pure geometry without attributes limits the model’s use for operation, analysis and evaluation.
- Missing tolerances: Without accuracy specifications, models are difficult to verify and may be legally vulnerable.
- Too much detail: Overmodelling increases project costs without necessarily adding value. LOD and LOI should always match the project purpose.
- Media breaks: Manual notes instead of digital workflows increase the risk of errors. Direct data capture as part of digital building surveying is more robust.
- Isolated data: Missing links to room books, MEP data or energy assessments leave valuable potential unused.
Existing Building Modelling vs. As-Built
- As-built documents the actual final condition after construction.
- Existing building modelling creates an up-to-date, usable 3D model of an existing building for scan-to-BIM workflows. It is often based on scans of older buildings and includes deviations, attributes and derived outputs such as plans or room books.
FAQ
What level of detail is useful for refurbishment planning?
For concept design and scenario planning, reduced LOD/LOI levels are often sufficient. For execution planning, more detailed building components and MEP elements are usually required. The level of detail should always be aligned with the project goal.
Which data is used as the basis?
Common input data includes point clouds, such as E57, LAS or LAZ files, from LiDAR or photogrammetry. Photos, 360° images and existing documents are often added to validate the building survey.
Which formats are used for delivery?
For BIM workflows, IFC is typically used. In addition, 2D plans are often delivered as DWG, DXF or PDF files.