Manual:BIM modeling

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Building Information Modeling is a process used in architecture, engineering, and construction to create and manage digital representations of physical structures. It integrates not only 3D geometry but also critical data such as materials, costs, and schedules, allowing for advanced analysis and collaboration throughout the entire lifecycle of a project.

In FreeCAD, BIM functionality has evolved significantly, especially with the release of version 1.0, where the previously separate Arch and BIM workbenches were merged into an integrated BIM Workbench. This consolidation streamlines workflows, allowing users to model, document, and manage building projects more efficiently within a single environment.

A major advancement introduced in FreeCAD v1.0 is the adoption of the Native IFC concept. Previously, like most BIM applications, FreeCAD translated data back and forth between its internal data model and the IFC (Industry Foundation Classes) file format, leading to potential data loss during the opening and saving processes. With Native IFC, FreeCAD users can now open, manipulate, and save IFC files directly, where the IFC file itself serves as the data structure. This approach eliminates unnecessary data translation and ensures that modifications are saved without rewriting the entire file, making it compatible with version control systems like Git and providing a more transparent, precise workflow for handling IFC files.

In this chapter, we will see how to model this small building:

Notice that we consistently drew the lines in the same direction (clockwise). While this isn’t required, it helps ensure that the walls we will build next have consistent left and right orientations. You might wonder why we didn’t just draw a rectangle, which would have been simpler. However, using four separate lines gives us the opportunity to showcase additional BIM functionalities, such as how to combine multiple objects into one, which is an essential part of the workflow.

If you didn’t draw the lines in the same order as instructed (clockwise), the orientation of some walls may be flipped, meaning they could be positioned on the opposite side of the line (to the right instead of the left). In that case, you would need to adjust the alignment to the right for those specific walls to ensure they all align consistently. Once this is set correctly, you'll have four walls that intersect at the corners, positioned on the inside of the baseline, forming the desired layout.

After creating walls, the next step is to join them so they intersect properly. This is necessary when walls don't connect cleanly at their intersections. To do this, you select one wall as the "host" and add the other walls as "additions", merging their geometry with the host. All objects in the BIM Workbench can have multiple additions (which add geometry) or subtractions (which remove geometry). These relationships can be managed anytime by double-clicking the object in the tree, allowing for flexible adjustments to ensure the walls and other architectural elements integrate smoothly.

The individual walls are however still accessible, by expanding the wall in the tree view.

Windows are always based on sketches. You can easily create custom windows by first drawing a sketch on a face, then turning that sketch into a window by selecting it and clicking the window button. Afterward, you can define the window's parameters—such as which parts of the sketch should be extruded and by how much—by double-clicking the window in the tree view. Now, let's move on to creating a slab:

With that, our model is now complete. The next step is to organize it properly to ensure it exports correctly to the IFC format. IFC files require all building elements to be grouped within a building object, and optionally, within a specific story. Additionally, all buildings must be located on a site. However, FreeCAD's IFC exporter will automatically generate a default site if one isn't present, so we don't need to add it manually. It's important to properly structure the model to comply with IFC standards, ensuring smooth collaboration and compatibility with other BIM software. Proper organization will also help avoid any data loss or errors during the export process.

Our model is now ready to export:

The IFC format is one of the most precious assets in a free BIM world, because it allows the exchange of data between any application and actor of the construction world, in an open manner (the format is open, free and maintained by an independent consortium). Exporting your BIM models as IFC ensures that anyone can see and analyze them, no matter the application used.

We can use the TechDraw Workbench to create a drawing of our building. The process is similar to what was shown in the previous section, so we won't go into too much detail here. Simply create a new view by using the insert Default Page option, then select the view you want to display in the drawing and add dimensions where necessary. This will allow us to create a professional 2D representation of the 3D model for documentation or presentation purposes.

Our page is now ready, and we can export it to SVG or DXF formats, or print it. The SVG format allows you to open the file using illustration applications such as Inkscape, with which you can quickly enhance technical drawings and turn them into much nicer presentation drawings. It offers many more possibilities than the DXF format.

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Generating 2D drawings
Using spreadsheets
Manual start


BIM