While there is a prevailing sentiment that building façades, being confined to the outer footprint of the building, do not need to be actively coordinated with other trades, there is immense value in doing so. Building Information Modeling (BIM) is inherently a holistic process to ensure successful consolidation of several construction trades, and façade contractors should play a key role in this process. By actively engaging in the BIM process, façade contractors can save time and money and unearth issues in the design and coordination phases, rather than dealing with a clash between trades models on the project site.
At Permasteelisa, an international façade design firm, we proactively engage in the BIM process at every stage of the project and benefit greatly. At the tender stage of the project, we frequently receive a 3D model from the architect. With the increasing complexity of projects, having a 3D representation of the architect’s vision has enhanced our ability to understand the design intent and provide a more accurate bid. Being willing to learn and adopt the architect’s tools gives us the ability to communicate quickly and efficiently with them. We use Catia, Rhino, and Revit in order to interface more directly with the architect’s model and extract geometry and metadata.
The anchors that transfer the load from the curtain wall back to the steel structures or concrete slab are very much intertwined with these structural elements, and it is essential to coordinate these connections. Not only is it easier to coordinate these interfaces in 3D, it is also more prudent to do so, as the 2D structural plans of the steel structure rarely show connectors like gusset plates or bolts. We frequently collaborate with the steel contractor to either shop weld our steel anchors or provide bolt holes for us to attach them. By sharing a model of our anchors in their native form, this information exchange is seamless and easily verifiable, decreases cost, and reduces risk on the job site. On several occasions we have had to coordinate with trades that penetrated or fastened to our system. Some examples include electrical conduit, sprinklers, crane tie-backs, and other temporary structures. Integrating these penetrations is easier in 3D where we can simultaneously account for their locations in plan and elevation. For our site teams, a merged 3D model of all trades serves as a quick and easy reference. It has proven to be a helpful tool to identify when something is out of tolerance and communicate that information back to the design team.
BIM is a powerful tool that can simplify communication in the design and coordination phase and save cost and labor in the factory and on the job site
Implementing the BIM process has its challenges, but there are some simple ways to address them. In the early stages of BIM, when all the models are in flux, it can be difficult to gauge how seriously to take a clash or even the position of an object. Establishing a line of communication with the other subcontractors and simply asking the questions about their model accuracy and status typically resolves these issues rather quickly.
There is also the question of whether or not the BIM model is or should be considered the contract document. The BIM model sometimes contradicts the 2D contract document. In our experience, when there is a discrepancy, it is easily resolved by bringing it up at a BIM meeting or writing a quick RFI. There is also a lot of benefit to establishing the 3D model as a contract document; for some complex projects we have had success with a 3D model - the project wireframe - being a contract document for the project.
For BIM to work successfully, all parties involved need to be proactive and BIM needs to be more than a requirement to fulfill. Ideally, early on in a project, all the subcontractors identify the areas where they interface with other trades and agree on a timeline for coordination that works for all parties involved. Adjustments to individual processes will likely be required, but it is well worth the effort for timely BIM coordination. In the last few years Permasteelisa has rearranged design timelines significantly. We now model the anchoring connections prior to the curtain wall in order to ensure early coordination with the steel and concrete subcontractors. We also provide a simplified model of our scope at the beginning of the project for early clash detection. In addition to the clash detection done by the GC, all subcontractors should visually check how their scope of work interfaces with the other trades. While clash detection is important, not doing a visual check runs the risk of missing “soft clashes”, i.e. items that would clash if tolerances worked against us.
Façade design is more complex than most think. By proactively engaging in the BIM process and being willing to learn and adopt new tools, our international façade firm has improved our design process and has a high degree of success with increasingly complex projects. BIM is a powerful tool that can simplify communication in the design and coordination phase and save cost and labor in the factory and on the job site.