Minimizing Risks in Existing Building Renovations: How 3D BIM Models can help
- 21 hours ago
- 4 min read
Reliable renovation planning starts with having the most accurate possible understanding of the existing building. However, particularly in older buildings, existing plans are often incomplete, outdated, or no longer reflect the actual as-built conditions.
A BIM model based on up-to-date survey data provides a reliable digital foundation for planning and can help identify discrepancies at an early stage and reduce risks in later project phases.
Why is a digital as-built model particularly important for renovation projects?
When planning a new building, the design is based on a defined planning status. Renovation projects have a different starting point: the building already exists – including alterations, deviations, and irregularities that may have developed over years or even decades.
Historical as-built drawings do not always accurately reflect these actual conditions. Walls may be positioned differently than shown in the drawings, ceiling heights may vary, or building elements may have been modified at a later stage.
If such discrepancies are only discovered during construction, the resulting design adjustments can lead to delays and additional costs.
A digital as-built model, by contrast, provides architects and planners with an up-to-date spatial basis for further planning. Depending on the project requirements, relevant geometric characteristics of the existing building can already be taken into account during modeling and subsequently incorporated into the renovation or conversion design.
How is a 3D BIM model of an existing building created?
The process begins with capturing the actual condition of the building. One commonly used method is 3D laser scanning, which captures the visible geometry of the building and generates a point cloud.
This point cloud consists of a large number of spatially defined measurement points representing the captured surfaces of the building. However, a point cloud is not yet a BIM model.
In the next step, the point cloud is evaluated in BIM or CAD software. Walls, slabs, columns, windows, doors, and other required building elements are modeled according to the project requirements. If required, the elements can also be enriched with alphanumeric information.
This process is known as Scan-to-BIM. When survey data is used to create conventional 2D drawings such as floor plans, sections, or elevations, the process is often referred to as Scan-to-CAD.
Importantly, not every project requires the same level of detail. Which building elements need to be modeled, what level of accuracy is required, and what information the model should contain should always be determined by its intended use.
How can BIM models reduce planning risks?
The key advantage lies less in the three-dimensional representation itself and more in having a reliable digital representation of the existing building that is suitable for further planning.
Planners can, for example, better understand spatial relationships and coordinate the new design with the existing building. Deviations, varying heights, or geometric irregularities can – provided they are part of the agreed modeling requirements – be taken into account before construction begins.
This is particularly relevant for complex existing buildings. The better the actual conditions are understood at the beginning of a project, the lower the risk of significant geometric discrepancies only becoming apparent on site.
A BIM model can also serve as a shared basis for different project stakeholders and, depending on the project, can be used for architectural design, MEP planning, coordination, or subsequent analyses.
From point cloud to a reliable basis for planning
In practice, renovation projects often begin with existing as-built drawings. However, these are not always sufficiently up to date to serve as the basis for detailed planning. The building is therefore surveyed again and, for example, captured as a point cloud using laser scanning.
To turn this data into a usable basis for planning, the survey data must then be interpreted and converted into a structured CAD or 3D BIM model.
This is where one important distinction comes into play: An accurate point cloud does not automatically result in an accurate BIM model.
During modeling, building elements must be interpreted correctly, geometric characteristics need to be assessed, and the previously defined modeling and accuracy requirements must be met. Subsequent quality assurance also plays an important role.
Errors or incorrect assumptions made during this process can carry over into subsequent planning stages. For this reason, it should be clearly defined before modeling begins how the model will be used later and what information and level of accuracy are actually required for that purpose.
Reducing risks starts with a reliable understanding of existing conditions
A BIM model cannot completely eliminate unknown conditions within an existing building. Concealed building elements or information that was not captured during the survey remain limitations of the model.
What a carefully created as-built model can provide, however, is a significantly better basis for planning: the captured condition of the building is structured and made digitally usable, relevant geometric deviations can be taken into account at an early stage, and planning decisions can be based on up-to-date data.
Especially in renovation and conversion projects, this can help reduce unexpected issues in later project phases.
Are you interested in 3D modeling (BIM) and would like to learn more, or do you have specific questions about your project? We would be happy to discuss your requirements with you.
Michael Danklmaier, Miviso Co-Founder
Tel.: +43 512 931824 200
Comments