Some history: The good ol’ days, the bad ol’ now
Hanging next to the security desk in the lobby of 48 Wall Street in NYC is a 1927 framed ink on vellum drawings of the cut stone façade. This 6’ tall drawing shows every block within a vertical sliver of the ornate stone façade. The details at the side of the page provide the dimensions of each block together with the direction and type of chisel marks and the dimensions and locations of anchorages. The drawing is so detailed that the masons who cut and set the stone could have done so by referencing the drawings. If the carpenters made the windows in the same way, the windows and stone would have fit together at the site.
This ink on vellum drawing required a high level of expertise on the part of both the architect and the draughtsman who created it. Most interesting to us, the skilled input of insider knowledge resulted in a drawing with a very high level of useful information content.
I recently heard an architect lament that their fees are now so low, the first thing they ask at a project launch meeting is “how little can we do?” Between 1927 and 2011, the requirement for the level of input exemplified by the drawings of 48 Wall Street has gradually faded as the industry changed and fees dropped, though in boutique firms, especially those with older architects who specialize in restoration, the detailed knowledge of building materials and methods is still alive.
The drawing in the lobby of 48 Wall Street was the work product of an architect who was also a master builder. Most BIM’s are the product of CAD techs who have little knowledge of the construction process, and therein lies the problem.
Most BIM output is little different than pencil-based drafting
Despite widespread acclaim as the “Next Big Thing”, BIM has a serious image problem. There is even anecdotal information that owners think the use of BIM increases costs.
In this context it is useful to note that the introduction of AutoCAD was not really a revolution in architectural practice, but simply a revolution in reprographics. In other words, the adoption of CAD did not result in a big conceptual change in the way offices worked or drawings got built, just in the physical way lines where placed on paper. So while CAD put computers on desks, BIM is supposed to be revolutionary.
Most big firms now use software like REVIT to generate “models” and something like AutoCAD to touch up the resultant drawings. I argue that parametric, manufacturing-ready drawing is truly revolutionary, while BIM as we know it is simply the evolution of CAD; not fundamentally different than drawing with a pencil.
Notionally, the use of BIM is intended to restore the central role of “the drawings” as a tool of construction costing, refinement and coordination. Therefore much is made of the elevated information content in BIM’s. But the fact is the vast majority of BIM’s are built by CAD techs using stock features generated by stair, wall and window tools that are native to BIM software platforms. This is in fact the point: low skilled techs supposedly doing the work of experts. These tools are intended to enhance productivity, but in my opinion they often diminish information content because they generate drawings with nearly ubiquitous sloppy geometry and unresolved connections.
The fact is I frequently see “100% DD” BIM-based drawings from major firms “issued for construction” with obvious issues such as partitions sticking through the curtainwall, floating steel framing, impossible stair geometry, etc. To deal with this widespread problem, in the final “output” phase of the drawing process, many architectural firms quietly drop the detail views extracted from the BIM model and generate detailed sections in AutoCAD, under the direction of the oldest guy in the office, just like the “good ol’ days”. Unfortunately, these details, while classic, end up as “orphans” with no scalable connection to the main model. In the worst case scenario, there are different details on every floor for recurring conditions, because several of these processes occured simultaneously, without reference to the model.
Groundhog-day BIM: Rebuild, rebuild, rebuild…..
The contracts issued to the trades typically throw the burden of clash detection on them, requiring them to analyze the available drawings for inconsistencies. This has created the absurd situation where the current practice for the structural steel, curtainwall, mechanical and miscellaneous contractors (people who have to actually cut and install materials) is to re-build the relevant portion of the model from scratch, sometimes with reference to gridlines, but sometimes with reference to the steel or concrete shop drawings. In many cases the contractor is not up to speed with BIM, so the subs must then exchange these models amongst themselves and much chaos results.
The bottom line is that because of a lack of constructability input and the use of BIM platforms, rather than manufacturing platforms, most BIMs produced can only be used for conceptual development, as a basis for rough bidding and to satisfy the demand for PR flythroughs. Sadly they cannot be used directly for modern, digitally-driven construction.
It started to change with CATIA and the Airbus A380
The design process of both the Airbus A380 and Boeing’s Dreamliner were almost entirely virtual. These extraordinarily complex objects and the tooling to make them were designed on a computer, files were sent to suppliers who manufactured bits and the bits fit together to make a plane that flew. In fact confidence levels were so high that in both cases, multiple planes were already in production when the “prototype” first took to the skies. To be honest, it wasn’t all a bed of roses, because these design and production techniques were in development during the project, so the planes were years late. (One of the best known errors that occurred was due to a lack of interoperability between versions of the CATIA software used by Airbus, resulting in miles of wiring that didn’t fit).
Despite setbacks, these pioneering efforts led to the improvements in CATIA software that made it useable for more fast-paced applications, such as the automotive industry and architecture. Subsequent adoption of 3D modeling by architects such as Gehry occurred alongside the development of specialized platforms such as TEKLA (structural steel) and SolidWorks (Industrial design and architectural fabrication) and led us to the present day, when use of 3D modeling in industry is widespread.
“Drawing is Building”: A return to the architect as a “Master Builder” and a cornucopia of value
The Airbus / Boeing story shows us that detailed, practical application of modeling technology is the key to successful construction. To realize the benefit of BIM, the construction industry must learn to use the 3D model in the same way that manufacturers do: As a tool of building production, not a tool of drawing production. This is a fundamental conceptual shift….back to a time when the architect was the master builder with buck-stops-here responsibility and the drawings were the underpinnings of the construction process.
This conceptual shift can be summed up as a shift from “drawing buildings” to “drawing is building”. In other words, a manufacturing-ready, cut-file-level drawing is built with vectors that are descriptors of solid bodies and those vectors are accurate and well-considered enough to be relied upon to guide cutters through material. (It’s worth noting that a side benefit of highly accurate models is dramatically better renderings…)
“Drawing is building” requires a heightened level of responsibility for arcane technical issues and acceptance of full responsibility for obtaining and verifying the knowledge needed to create cut-file level computer models. Designing original high-end work so as to avoid delays and rework at the site requires an in-depth understanding of exotic work practices. This in turn means that iconic projects which leave the world of catalogue architecture behind require the unique, skilled working methods that continue to be the greatest source of frustration for detailers and owners. For years the automotive and aerospace industries have been avoiding the pain of skipping this step by employing specialists for each component of large projects and by establishing relationships with suppliers whereby the suppliers add their models to the main body of work.
The problem is that just like the aerospace and automotive industries; the detailed knowledge that is needed to inform modelers is in the hands of specialists and fabricators, but these have no interest in helping design the building if there is no contract in place. So like “the good ol’ days”, the architect and their designers must get out of the office, visit sites and learn the intricacies of the trades whose work they want to learn to model correctly. To help eliminate the mundane details from this process, many manufacturers of stock building components now share models online, thus increasing the chance that their product will be specified. Unfortunately, the world of custom work will remain a black box for the foreseeable future, but distinguishing between the areas that are and are not challenging will help extend meaningful modeling to a larger range of project components.
Final thought: Embrace risk, be awarded
Since it is clear that risk can be managed by powerful and effective modeling techniques, is risk really risk? Since the construction business is essentially a sophisticated, elastic mechanism for risk / reward allocation, ambitious architects and contractors should embrace risk rather than running screaming in the opposite direction. And owners should care…..the extras that result from unmanaged risk come out of their pockets, one way or another.
Copyright Julian Bowron 2012