The Red Herring Called BIMThe Red Herring Called BIM
By Gary Orazio
It seems with each passing week there is another article, conference, or seminar from a member of the design community about the virtues of BIM and why the entire design community should be fully endorsing a unified direction. Many of the efforts are centered around the adoption of, and unbridled enthusiasm for Revit, a product of AutoDesk, as the sole design platform. What is lost in translation is the fact that the design industry is not homogenous, but is split into two categories, architecture and engineering, each with very distinct needs. Included within the engineering category, for the purposes of this article, are the mechanical, electrical and structural disciplines.
In general, architectural documents provide design intent and are intended to be used as a guide to construction when used in conjunction with code requirements and industry standard construction details. Take for example a metal stud and drywall partition: The wall is defined by industry standards and codes, and therefore stud construction and drywall connection details are typically not required. In more complex systems such as curtain walls, the construction details are provided by the curtain wall supplier because each system is unique to the supplier. For these reasons, a product like Revit works well because it is primarily a design intent tool, not a fabrication platform.
Unlike architectural systems, detailed engineering documents are required for construction of the mechanical, electrical and structural systems which are typically not proprietary systems. Detailed construction documents are critical to the construction process particularly with the advent of automated fabrication and the acceleration of offsite prefabrication. Details from the design documents can be input directly into the fabrication equipment. This fabrication and prefabrication process is utilized on all piping and sheet metal systems. On most projects, the BIM process is being run by the architect or General Contractor who tend to have little understanding or appreciation for the inefficiency of the process on the engineering and primary subcontractors. On the vast majority of projects today, the development of a native Revit BIM model has little value to the actual process of constructing any of the mechanical, electrical or structural systems in a building. Most, if not all, of the effort by the design team to develop a BIM model is not used by the primary subcontractors to build the project. This begs the questions of: how did we get to this point and where should the design community be headed?
A little recent history may help to better answer the question. Sometime during the late 1970s and the early 1980s the design community began a process, advised by their insurance carriers, to minimize their potential professional liability on projects. As part of this process, the notion of not defining means and methods expanded to minimizing and excluding basic constructability details. The infamous notes "contractor to coordinate" et al. begun to show up on plans and documents and as a result threw more and more of the design and layout efforts on the contractor teams. A generation of architects and engineers were proud to state that they were great at "solving problems in the field" and young designers learning from their mentors believed that that was the way design was done. "Don't worry about the details if the contractors cannot figure it out…they will call!"
The first consequence of this approach was to move the design documents further and further from having any semblance of the actual detail required to construct a project. The large conceptual design and engineering points were covered, but any additional details were left to the contractor to figure out. The second consequence was an increase in cost to the owner through field coordination related change orders.
In response, the primary subcontractors had no choice but to begin assembling in-house teams whose job was to finish the design to a level necessary for the field forces to know what needed to be constructed. This transition of talent began in the sub-trades about 10 to 15 years ago. As automated fabrication processes for sheet metal and prefabrication of piping began to take a more prominent position, the need for accurate fabrication drawings became more critical. The sub-trades had no choice but to try to bring design and layout in-house because they were not getting anything usable from the vast majority of design documents. Although today BIM and constructability are the topic of every architect and general contractor, they are still 10 to 15 years behind the primary subcontractors.
In response to the needs of the sub-trades, a handful of engineering consultants began to move into the constructible documents arena. The goal was that their drawings could be used as the basis for fabrication and spool drawings. To accomplish this goal it requires using software that can be used in the primary subcontractor's fabrication processes. These fabrication software products have been in use for well over ten years and are currently not compatible with Revit. The fabrication software is AutoCAD based and can be uploaded into Revit models; however, the details required for fabrication do not translate. Revit serves the architectural community well because the vast majority of architectural drawings confer design intent, not fabrication details. The requirement that the engineering supporting the primary subcontractors is to be done in native Revit reduces the usefulness of the engineering documents.
In response to the requests of the architects and general contractors, the vast majority of engineering firms have transitioned to Revit and as a consequence have continued to digress to providing even less detail, relying on the contractor to redraw the documents and in many cases complete the detailed engineering design. This results in the increased construction cost of the project.
Currently, BIM, 3D documents and constructible documents are used synonymously; however, the fact is they are very different in scope and complexity. They actually build on one another. At the beginning level is 3D documents, which is where the vast majority of firms are operating. This simply entails developing drawings in all three dimensions. The goal is to allow coordination or “collision checking” between disciplines.
The second step is developing a design in constructible documents. Constructible documents are not only in three dimensions, but also include all of the details required to physically construct the project from the documents. They eliminate, or at the very least minimize, the need for a new effort to create shop drawings.
Finally comes BIM, Building Information Model. BIM refers to documents that are not only constructible, but carry embedded information. The National Building Information Model Standard Project Committee has the following definition:
Building Information Modeling (BIM) is a digital representation of physical and functional characteristics of a facility. A BIM is a shared knowledge resource for information about a facility forming a reliable basis for decisions during its life-cycle; defined as existing from earliest conception to demolition.
Although lofty in its ambitions, BIM is a yet to be realized goal. Despite the popularization of the term, most firms are just beginning to operate in the 3D design world on a limited basis.
This brings us to today with the frenzy of activity and articles that have been written touting the benefits of Revit-based BIM. These articles written primarily by the architectural and general contractor communities completely ignore the 15 years of fabrication history of the primary subcontractors. So what is the result of all of this? Here are the key points:
- Any design work required to be done in native Revit will currently need to be redrawn by the primary subcontractors. The two primary reasons are that Revit does not have the detail necessary to allow construction, nor does it have the capability to translate into the fabrication software used by the primary subcontractors.
- The more engineering firms use BIM to create a design model rather than fabrication ready documents, the further they get away from the real point behind what we are paid to do, which is help a client construct a project.
- Until, or unless, the engineering community retakes the lead position in constructible documents, it will continue to be relegated to a lesser role and further lose their position as one of the advocates for the owner.
So why is BIM a red herring? While engineering firms are off pursuing the BIM model as defined by the architects and general contractors utilizing Revit as their sole platform , they are losing their focus on what is important; namely, the development of documents that can be directly used by the contractor team to construct the project without further redrawing effort. Without refocusing their attention on what is needed today, rather than on a lofty future goal, they will find themselves left out of the design and construction process.
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