What to Expect from BIM

When moving to a BIM work environment, you’ll experience a change in process and workflow.
Perhaps the most immediate and obvious difference is that a traditional CAD system uses many
separate files to document a building, whereas a BIM project typically has only one file. With
CAD, all the separate files are created individually and have no intelligent connection between
them. Each drawing represents a separate piece of work to be managed and updated throughout
the design process. With such an unwieldy process, the possibility of uncoordinated data is very
high. The change management required by CAD is a tedious and error-prone process that requires
diligent project management and lots of red lines. BIM provides a different approach to the problem:
Rather than many files, you work with one file. With BIM, all information is consolidated and net-
worked together for you, and the resulting drawings all relate back to a single underlying data-
base, guaranteeing an internally consistent model.
If you understand the basic premise of an integrated building model, then you’ll by now have
realized that BIM removes the concept of drawing lines to represent objects. Instead, you build
walls, roofs, stairs, and furniture. You model the building and its systems. Figure 1.2 shows a 3D
sectional view of a Revit model. You can see that the model incorporates façade elements, floors,
roofs, parapets, curtain walls, and materials. All this information is modeled and must be designed
as it is to be built. You then add layers of information to the drawings to explain the model, in the
form of parametric tags and keynotes. Although the end result is still a set of printed lines, you
rarely draw these lines. This concept of modeling is so simple, so natural, that you’ll get used to the
idea in no time and find yourself dreading the idea of ever having to go back into the 2D realm.
Revit is excellent at managing changes and keeping your model interconnected. Unlike CAD,
the intent of BIM is to let the computer take responsibility for redundant interactions and calcula-
tions, providing you, the designer, with more time to design and evaluate your decisions. As the
architect, you hold the design decision process in your hands. With a BIM tool such as Revit, be pre-
pared to change your expectations of how to use design software. Remember—you are modeling
a building now, not drafting lines. You’re doing what you do best: solving complex 3D problems.
As you move into a more advanced Revit workflow, we want you to keep some concepts in the
back of your mind.