by Erik Sanford
In the increasingly complex world of design, construction, and building operations/maintenance, building information modeling (BIM) enables exceptional vision and management with incredible speed and offers significant opportunity during the preconstruction process.
I have witnessed, over the past 20 years, the incredible growth that modeling has experienced within the industry, as well as the tangible, impactful results that a BIM can help us — designers, builders, and owners — to achieve together. Whether used for putting together an estimate, or planning where and when to construct and install, a model provides the ability to see from multiple angles, as well as with both macro and micro lenses, what I like to call “BIM vision.”
In my experience, this BIM vision, guided by skilled preconstruction teams, brings an unparalleled advantage to the process during the design phase of a project.
As a designer creates items within a BIM, each item exists as a specific object, i.e. doors, windows, walls, etc. Every object also has a corresponding set of parameters that allow for automatic reference to calculations, as well as notes and details from contract documents. All those parameters and levels of data help at the preconstruction and estimating phase with generating quantities directly from the BIM. The associated data (the “I” in BIM) is searchable, sortable, and accurate — and reflects real-time changes and updates. Data within the model allows the experienced estimator to see what was counted (and, equally importantly, what wasn’t) and generate accurate and predictable estimates and plans.
Alternatively, developing a plan based on 2D documents can be complex and take a significant investment of time— days, or even weeks or months. A CM must then attempt to explain the plan in meetings that often cover multiple aspects of a project, leaving room for confusion. The visual, three- and four-dimensional nature of the model can provide the CM with clearer understanding of design intent and the owner with clearer construction intent. The fourth dimension of time can be added
to a model by linking schedule tasks to elements within a model to show when and where different work is going to be completed. Developing time-enhanced models tests the plan — like a dress rehearsal for major, complex construction. Here, the project team can identify any possible misalignments in the plan and correct them. Ultimately, the project team has greater confidence in the plan because it has been tested, and everyone proceeds with better alignment and a clear, shared understanding.
BIM vision can also help in looking at specific design assemblies. For example, a column enclosure needs to be created in a room that is already very tight. Different enclosure options can be tested in a virtual mockup approach. A planner working with the architect can model out the different options as they would be built. The best option can then be picked with greater confidence knowing that it has already been tested. This timely collaboration between CM and architect will also improve the subcontractor submittal approval process. I have experienced great success with this approach over the years. The trust that is created with collaboration like this is invaluable; it enhances communications, and earlier, more comprehensive solutions.
It is important to note there is a difference between a design model and a construction model, and each has a purpose. Design models primarily provide important documentation and energy analysis information, while construction models allow teams to test constructability and run spatial coordination analysis.
Erik Sanford, CM-BIM, CM-LEAN, currently spearheads Dimeo Construction Company’s Virtual Design & Construction Group.
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While simplified, these examples show the differences in purpose that lead to differences in approach. As a result, perhaps a wall in a design model may be shown from slab to slab with full height GWB, but will not necessarily be built that way. It may actually be built (and estimated) as framed slab to slab, with GWB stopping just above the finish ceiling. The raw area and height dimensions for this wall in the design model will be different than that in a construction model and in the estimate. Models are not perfect and at times elements aren’t modeled, or duplicates of elements are; whether a design or construction model, it is only as good as the level of effort that is put into it.
Developing a strong partnership with the design team during pre-construction is beneficial to all. Even if the models being shared are in a “raw” state with generic placeholders, the team can still visualize the design intent and come to more certain decisions faster. Collaborating with designers and owners that see the value in sharing models and working together during the preconstruction process enables all of us to make more comprehensive decisions with greater clarity and certainty, ultimately facilitating the construction with less opportunity for changes.