BIM (Building Information Modeling)
For all of the history, design and construction of building have relied on drawings for representing the work to be done. They were defined as contracts - legal documents, were assessed by building codes, and used to manage the facility afterward. But there are two strategic limitations of drawings: (1) they require multiple views to depict a 3D object in adequate detail for construction, making them highly redundant and thus open to errors; (2) they are stored as lines, arcs and text annotations that is only interpretable by some people; they cannot be interpreted by computers.
BIM involves representing a design as objects – vague and undefined, generic or product-specific, solid shapes or void-space oriented (like the shape of a room), that carry their geometry, relations and attributes. The geometry may be 2D or 3D. The objects may be abstract and conceptual or construction detailed. Composed together these objects define a building model (not a BIM, in my view). If an object is changed or moved, it need only be acted on once. BIM design tools then allow for extracting different views from a building model for drawing production and other uses. These different views are automatically consistent - in the sense that the objects are all of a consistent size, location, specification - since each object instance is defined only once, just as in reality. Drawing consistency eliminates many errors.
Modern BIM design tools go further. They define objects parametrically. That is, the objects are defined as parameters and relations to other objects, so that if a related object changes, this one will also. Parametric objects automatically re-build themselves according to the rules embedded in them. The rules may be simple, requiring a window to be wholly within a wall, and moving the window with the wall, or complex defining size ranges, and detailing, such as the physical connection between a steel beam and column.
Architects, engineers, owners, contractors and building product manufacturers have been part of an amazing, and rapid transformation in how we communicate our building designs. We have gone from hand drawing, to CAD, to BIM is less than 25 years. This transformation has resulted in opinions as to which is best, fastest, results in the best designs.
I. Hand Drawings
The first phase, hand drawing, has lasted for thousands of years. Over all those years, a consistency developed in the way contract documents are laid out, graphic standards used, and drawing sets organized. Interestingly, this consistency is an international language for drawings. In viewing drawings from many different countries, although the languages are different, the drawings are very consistent. And, one could easily conclude how a building was going to be built and how it would look. This consistence in contract documents has been a long process of trial and error, aiming for perfection, of the best way to communicate the designer's intentions to the builders.Hand contract documents are beautiful but not the creation process. Some designers spend some days erasing more than drawing. Every time a change is made to a plan it means days of changes to background drawings for reflected ceiling plans, electrical, mechanical, structural, plumbing and details drawings. The chances for errors and omissions were tremendous.
CAD has only been around a few years, but has been an important advancement. It will be replaced, but has been an important transition to the more powerful future. CAD taught designers about computers, file management, and new organizational skills. CAD has been an amazing event. Instead of drawing on paper, you draw on a computer and see your work on the monitor. Fundamentally, CAD replaced hand drawing but did not substantially change the process or the way the information was displayed. A page of drawings was replaced with a drawing file. Instead of spending days or weeks creating background drawings, they were ready instantly. Unfortunately, if you changed the base drawing, you still needed to swap out the old backgrounds for the new. Errors and omissions were not eliminated, but they were reduced. For example, dimensions were accurate. CAD based contract documents can be created much faster than hand created drawings. CAD started as 2D only, but has now progressed to 3D. To date, it has not progressed to the level that it is practical to try to create a complete project in one 3D file.
BIM is the future of architecture and engineering drawing and documentation (and much more: analysis, rendering, costing, purchasing). BIM will lead to changes in process and procedures, as well as monumental cost savings throughout the entire design, building and management phases. However, in many ways, BIM is a promise of what will happen. the extraction of information from the BIM project is the ultimate power of BIM and the automation that will come. Structural engineers are leading in the extraction of data from the BIM model, with energy analysis close behind. However, we are just at the beginning. Most are using BIM to create contract documents that look like hand drawn contract documents. There continues to be great concerns about releasing the BIM models to the contractors. This will change. We need to be careful not to focus on making BIM look like 2D contract documents, such as fixating on graphic standards. We have a new very powerful graphical and data tool. We should be experimenting with how to take full advantage of this power. Architect normally do 3D sketches at construction sites to help workers better understand what they were supposed to build. Workers will use the BIM models at the job site, in 3D, to better understand what they are building. Automated QTO and costing will be a byproduct of the model. Contract document sets have grown in quantity of pages in the last few decades. If you review the number of drawings it took to build a major building 80 years ago, finding a set of over 100 sheets would be the exception. Today, contract documents for a similar building could easily number in the hundreds, if not thousands of sheets. It is hard to imagine how they can be comprehended. Perhaps the future will find no sheets; the BIM project file will set the contract scope of work, with no specific drawings.
While CAD has been criticized as distracting from design, BIM offers the potential of dramatically increasing the quality of design. Design is much more than a "pretty building", which is certainly one goal of design. Good design also includes designing to the budget, insuring energy efficiency, consideration of maintenance and renovation costs, analyzing structural options and much more. BIM will bring real time "what ifs" and analysis to the design process.
We have designed, documented and built our buildings essentially the same way for hundreds of years, no matter if it was drawn by hand or in CAD. BIM offers the very real potential to completely change the process, the form of documentation, responsibilities, liabilities and the amount of money.