Heritage Reconstruction: How to Reduce Costly Errors Using 3D & BIM. Part 2
August 27, 2024 at 7:00 am,
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To fully leverage the benefits of Building Information Modeling (BIM) during the design process, initial condition (inventory) models must be created. Ideally, this should be done using 3D survey data as discussed in Part 1, although in some cases, standard measurement methods or a combination of both can be used.
Modelling the Existing Conditions
Creating Historical Building Information Models (HBIMs) is notoriously challenging and often overly complicated. When working with historic buildings, it's important to recognize that none of the elements in real life are perfectly straight. This means that even two similar types of columns or windows are likely to differ in size or shape, sometimes significantly.
Current technologies for creating HBIMs typically do not allow for extremely high accuracy. Even when they do, the resulting models often become overly complex and impractical for design purposes.
For this reason, I recommend not overemphasizing the accuracy of existing conditions modeling. The same applies to the level of detail.
Section in 3D environment of a historic building design model
I recall a presentation by a team involved in the BIM creation for Westminster Abbey. Initially, they created a highly detailed and visually accurate BIM that closely resembled the real structure. However, they soon realized that it was too complex and slow to use for anything beyond marketing. Consequently, they decided to create a simpler model that was more practical and fit for purpose.
As mentioned in Part 1, it is also possible to use a combination of BIMs and 3D meshes if that approach is acceptable.
In any case, the people who will be using the models later should be involved in their creation. Often, when a third party is responsible for the model's development, it may end up being unusable for the intended process.
The Benefits of BIM in the Design Process
In the BIM process, creating models is both one of the most challenging and crucial tasks, serving as the foundation for leveraging other BIM applications.
First, if 3D surveying and model creation are utilized, there is a significantly higher likelihood of reducing design errors. I've seen numerous cases where major errors were made due to insufficient initial data when comparing 2D design information with 3D surveys.
To maximize the benefits, as with new construction, I recommend utilizing the four core BIM applications:
- 3D Visualization of Design Solutions: Walking through the existing building with the new design solutions in a 3D model provides a much clearer understanding of the design intent. It also helps ensure that the design prioritizes occupant well-being. As a client you can use different free tools to view the models. Some free tutorials can be found in the Free Guides section.
Modern MEP systems inside a historic building. Fitting them is always a challange. - Quantity Take-Offs (QTO): I would argue that QTO from BIM is even more critical for historical buildings than for new constructions. Designers and contractors often include large contingencies due to inaccuracies in the design. In one case study for a public client in Latvia, we estimated that the average artificial quantity increase (excluding the standard reserve in the Bill of Quantities) was around 10%. In other words, for a 10 million project, an additional 1 million was added "just in case."
- Constructability: Using models to verify that everything fits is essential, especially in heritage buildings where there are far fewer options for maneuvering new MEP (Mechanical, Electrical, and Plumbing) systems. In my experience, 2D designs for such buildings are often incorrect.
Design error found: MEP elements not fitting inside shafts in historic buildings. Fixings this during construction might be impossible. - Drawing Generation: If significant effort is invested in creating models, then the drawings must be generated from those models. If this is not happening, all other benefits will be nullified. A true BIM process occurs when the drawings are extracted directly from the models. You can read more about this in my blog post "Why Drawings Extracted from BIM Outshine Traditional 2D Processes for Your Future Family Home".
To learn more about the 4 Core BIM benefits, read my blog post "4 Most Beneficial BIM & 3D Uses for Small (and Large) Scale Projects".
Conclusions
There is little doubt that utilizing BIM in heritage reconstruction projects can not only reduce errors and unexpected costs during construction but also lead to design solutions that fit the building well and support occupant well-being.
The BIM applications mentioned above are not the only ones that can be leveraged. For instance, tools exist that allow you to compare 3D surveys with models to identify deviations, which can help structural engineers design safer buildings.
Facade deviation from a perfectly vertical plane of a heritage building. Top part is inclined outside more than 30cm.
If you own a historic building and are planning a reconstruction, my advice is to hire architects who work with BIM and, if possible, involve other designers who do as well. Utilizing the four core BIM uses in your project may involve higher initial costs, but the benefits can far outweigh them.
For tips on finding the right architects, see my post on the topic.
Lastly, remember not to overcomplicate things—BIM for historic buildings doesn’t necessarily mean creating complex, highly accurate models. Focus on what’s practical and beneficial for your specific project.