For thousands of years, architecture has been worked the same way. The tools have changed, from drawings on papyrus or chipped into stone, to drafting on velum and blueprints. The shift to CAD, computer aided design or drafting, was a major shift in the speed of production but doesn’t really change the way architects work. It was, and still is, essentially drawing on a two dimensional surface. It doesn’t matter if that surface is a sheet of paper or model space in a computer file.
What makes BIM different?
BIM is like building in a virtual environment. The property can be accurately modeled, with the topography recreated and the climate set as part of the information. This includes items such as humidity and temperature, solar information and elevation. The materials used can be accurately described, not only by size but with information that can include insulation values and life cycle costs as well. A CMU, concrete modular unit or concrete block, can be accurately dimensioned. A CMU is 7-5/8” x 7-5/8” x 15-5/8” in size. The drawing convention has been to use the nominal size of 8” to represent this. With BIM we can accurately model a wall with real dimensions which helps during construction as less assumptions must be made.
What can BIM do that CAD can’t?
Information is the most important aspect of BIM. The accuracy of design is much higher and more controllable. This doesn’t just include dimensions but material quantities as well. The content of a material such as cast in place concrete can be much more accurately estimated which can save on costs. The building energy uses can be extrapolated from the model to more accurately size AC equipment. This means equipment can be specified that isn’t too big or to small for the building. This information is not just useful to clients and architects but to contractors as well. They can more accurately price out a project because their material needs are more precisely known.
What are some of the issues with BIM?
The adoption of BIM by design professionals is very limited at this time. There are a few of reasons for this. The first one is the reluctance of established practitioners to make major changes to how they work. BIM is a paradigm shift in how architects design and is not an easy change to undertake. Another issue is once the decision to shift from CAD to BIM is made, the learning curve is very steep and long. It may take up to a year before a design team becomes proficient in the software. During this transition production time may actually be longer than before, however the benefits in the long term will be immense. Finding personnel who can use the software is also an issue. The people who know how to use the software don’t usually have the experience in construction to exploit it fully. Conversely experienced designers don’t know the program.
Our experience with BIM:
There have been two major advantages that we have benefitted from using BIM. The amount of time required for construction document production has been reduced significantly. Depending on the project, we have seen time savings of 50-90%. The accuracy of modeling has resulted in fewer construction revisions and RFI’s, requests for information. The most important change has been how we work with our clients. We deliver 3D models as part of the design process in addition to conventional plans. In many ways, we have found that clients, and in some cases engineers, have a better understanding of their project using the 3D model verses the plans. This allows us to have a very interactive design process and deliver a better project.
BIM has become the foundation for construction and as it is adopted more widely in the future by all members of the building team, will continue to be more useful in making design decisions.