CAD vs. BIM Files: 3 Major Differences

For decades, product design engineers have used computer-aided design (CAD) programs — such as Autodesk’s AutoCAD — to design various parts and components. These sophisticated programs are capable of creating extremely detailed 2D and 3D models.

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But more recently, building information modeling (BIM) — the process of laying out building systems, such as plumbing, electrical, and HVAC systems — has more increasingly become the new industry standard. BIM files serve as an indispensable tool for architects and construction professionals, particularly those working in commercial building.

With BIM files growing in demand among leading architecture firms, many building product manufacturers about — one of them being, “Can’t I just convert CAD files to BIM files?” The short answer: No. CAD and BIM file types differ in many ways, making a successful conversion nearly impossible. Below, we’ve outlined three major differences between the two.

Performance Characteristics

bim-performance-characteristics.pngCAD files are complex file types containing a huge amount of information, including part performance characteristics. 

Performance characteristics are critical in ensuring part reliability and longevity. For example, even if a part physically fits in its specified location, this is means little if its pressure ratings are too weak for the application or if it’s made from a material that interacts poorly with a substance in the end system. 

Performance characteristics take up a lot of file space and are generally purged during a CAD-to-BIM conversion. An end user looking at such a file would either have to acquire a separate spec sheet or, more likely, contact a different vendor.


bim-behavior.pngBuilding information modeling files are designed to behave in specific ways depending on their unique purpose and connection requirements. 

In other words, different components of a model “know” what they are supposed to do. A light fixture knows it must be attached to a wall or ceiling and the electrical system; a faucet knows it must be attached to a pipe; an HVAC duct knows it must be installed within a wall. As a model is altered, these types of components self-adjust in logical ways.

View Settings

bim-view-settings.pngCAD models have only one visual representation: highly detailed.

BIM models are designed for plasticity — they can be zoomed in on and out of, expanded, contracted, and so on. Introducing a static, high-detail component like CAD model into a fluid, changeable BIM model will allow for the CAD image to be viewable as intended, in full detail, at only one particular zoom level. Adjusting the scale of the model a little will result in blurring of the CAD component, while adjusting the scale more drastically can cause the image to discolor, become misshapen, appear as a black splotch, or disappear from the screen.

CAD file components lack this knowledge when they are incorporated or converted to BIM file types, failing to self-correct as adjustments are made to the model.

Learn More

CAD files are critical tools for manufacturers and many of their clients, while new technologies such as building information modeling provide manufacturers — building product manufacturers in particular — with even more sophisticated modeling options. To ensure smooth, timely processes, it’s critical to understand the difference between two, as their unique properties prohibit the possibility of practical CAD-to-BIM conversion.

For more information on the differences between CAD and BIM files, as well as the challenges involved in converting them, download our comprehensive white paper, “The Pitfalls of Converting CAD to BIM.

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