The Business of BIM Part 1 of 2

Published November 11, 2007

by Cyril Verley, RA

The buzzword these days is BIM: Building Information Modeling.

There is no doubt it's the future for the AEC market. There is also no doubt it's not a simple and easy transition. Going to BIM is not just a change of technology. Going to BIM is a business decision made by the owners of the firm knowing full well it will impact ALL levels of their entire business organization.

Most BIM models do many things. But the fundamental reason why BIM is overtaking our industry has to do with a Coordinated Document Set. Our profession can no longer afford non-coordinated document sets. Owners, developers, contractors, and even government institutions are demanding their projects be done in BIM for this fundamental reason.

BIM's Database vs 2D CAD
To help clarify the differences between BIM and traditional 2D computer aided design (CAD), let's compare a series of MS Word documents and an Access database. Two word documents by nature are not connected in any way and require a user to manually create a connection between them. However, two reports from an Access database allow the user to view the same data in two different ways. If the user changes the data, both reports update.

Traditional 2D CAD works much like the Word document: a plan file does not inherently connect with an elevation or section file since these are separate files. A true BIM is a database where the data is the project model and the reports of the database are the queries (or views) of that model. Hence all plan views, section views, elevations, callouts, perspectives, even schedules are live within a single project model. A BIM allows users to make a change in one view and have that change update in all other views across the entire project.

A true BIM should also allow a user to import and export to traditional 2D CAD. The "Purest" wants to keep the entire project as a separate BIM. However, for most offices transitioning to BIM, the reality of their first few BIM projects will include importing 2D CAD files thus creating hybrids of both BIM and 2D CAD. Again, this is typical during the transition to BIM and should be considered a success for the first project. Eventually, all the users will be Building Information Modelers but until then, traditional 2D CAD will be part of our design process.

Draw it Once
In a traditional CAD design environment, it is often the case during the schematic design phase of the project that a temporary 3D model is built using one software program (like Sketch-up® or Rhino®). Once schematic design (SD) is over, it's typical that this same 3D model is discarded as the project moves into 2D CAD production using a different software product (like Autocad®). If the 3D model remains, it will sometimes be updated in tandem with the 2D CAD files but this additional work is not automatic. Changes in the 2D CAD files do not update in the 3D model because the users are using two different software programs. When the CD phase begins, the 3D model often is out-of-date with the CAD files and is no longer an integral part of the production phase. Once the CD's are done and the project moves into Construction Administration, it is often that the contractors will build their own 3D model for costing and clash detection.

A true BIM model is built once during the early schematic design, is refined in design development (DD), and is used for the CD set. And for those firms lucky enough to have a strong relationship with their contractor, that same model can be passed along to the contractor for their costing and clash detection. Once again, the design process of our industry is being streamlined by BIM. It has already begun where the clients are demanding that BIM be used for pre- construction, during construction and for post construction facilities management.

3D, 2D or Both
There is a misconception that BIM is all 3D. Excluding the importing of 2D CAD, a true BIM is both 3D and 2D. The level to which one builds the model in 3D depends on the needs of that client. An architect's BIM is partially 3D and 2D. There is no need for an architect to draw a backer rod or window flashing in 3D. Items such as these would be drafted as 2D elements. That detail view now includes 2D annotation and graphics placed on top of the 3D elements from the model or in a separate 2D view.

On the other hand, a BIM for a contractor is a very different model and typically requires a higher percentage of modeling in 3D. If the contractor needs to phase the model for site logistic diagrams, the model needs to be reorganized to clarify when elements in the model are built and when they are removed; this requires the elements modeled in 3D. From a cost estimating point of view, the contractor needs to be able to extract quantities from the BIM thus increasing the probability that components like backer rods or window flashing be built in 3D. Once built, these same 3D BIM components can be scheduled from the model, counted and then priced.

The last is coordination for clash detection. The contractor will have an interest using the BIM in determining clash detection between various trades such as architectural, structural and MEP prior to the construction of the project. The ideal scenario for a contractor is to build each project twice: the first construction determines all the errors and clashes which guides a smooth construction the second time around. In this case, a BIM is the first model and the live construction is the second model.

BIM is Changing the Design Process
In the past, it was often the case that the more experienced architect with less knowledge of CAD was held hostage by the CAD jockey with less architectural experience. Unlike traditional CAD, a true BIM software application is less about non-architectural CAD terms like "x-referencing", "paper space" or "display level" and more about architecture and architectural issues. BIM is ideally suited for an experienced design professional who can guide the junior staff. Since more discussion with team members is about architecture and less about CAD, BIM is reactivating the once lost Master / Mentor relationship.

When using BIM, the design professional must also reeducate their clients as to changes in the design process. These changes include client drawing submissions, contractual agreements (for example, "BIM Consensus Documents Addendum #301"), and a realignment of how the scope of work is divided per phase.

For example, BIM requires a dramatic change in the process of what a design professional would submit to a client. Since a digital model of the project is being built, more decisions are being made sooner which requires more time during the schematic design phase. Instead of schematic design representing about 10% of the overall scope of work, BIM has changed the amount of time required for SD to about 35 percent. These early decisions do not need to be final and can be made up of generic model elements as place holders.

As the project enters the design development phase, again this phase of the project will become about 15 to 20 percent of the overall project scope. Once the project reaches the construction documentation phase, the remaining 45 to 50 percent of the project remains for dimensioning, annotating and detailing. In fact, I have had clients tell me they were 40 percent done with CD's by the time they reached the end of their BIM DD phase.

The true benefit of this process is that BIM will force the architect to address design issues more evenly throughout the project. This is not to say that the design intent has to be finalized in SD. The architect can respond by building the BIM with "generic" architectural elements and during the design process, change those elements to suit the design intent. If these design issues are addressed sooner, there are fewer surprises once the CD phase is reached.

Another added benefit comes when the BIM is shown to the client. Creating hidden line 3D views of a BIM is quite fast and can be easily produced for a client meeting. If the client is viewing a set of three dimensional isometric or perspective images during a design review, there is a higher probability they will make decisions sooner regarding the direction of their project. This single item alone is worth the effort of implementing BIM within an AEC office.

Cyril Verley, founder of CDV Systems has been practicing architecture for 23 years, registered for 18, an AEC consultant for the past 15 years with the last 7 years focused on Revit services (14 months prior to Autodesk's purchase of Revit). He can be reached at

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