The Dimensions of BIM
by Holly Allison
“So, do you do BIM?”
How many times have you been asked that question during presentations to Owners?
BIM stands for Building Information Modeling. We’ve all seen the fantastic models that architects, GCs, and subs produce to help the Owner visualize their work; now let’s break down the dimensions.
2D BIM: As much as we would like to change commercial construction contract law, the 2D drawings remain the cornerstone of the contract. The BIM model is typically used to produce these 2D drawings.
What tools do you have in place to organize the 2D drawings you receive? Do they land on your desk with a thud at the eleventh hour? And is it your job to catch all the changes made between this version and the last version you received? It would be advantageous to have a Drawing Registry which automatically collates and compares the different versions of 2D vector-based PDFs and DWGs. It would locate the changes so you can mark up the drawings with clouds, comments, questions, and even provides a collaborative workflow so you can assign teammates to investigate the changes.
3D BIM: This model represents the geometry of the building and is a collection of objects such as walls, slabs, columns, doors, windows, etc.
As more models become available, coordination and clash detection come next in the workflow. Clash detection is all about BIM objects and where they intersect each other. Constructability combines clash detection with 2D and 4D information to provide a much richer and more comprehensive coordination process.
4D BIM: the combination of time and geometry creates the fourth construction dimension. We define 4D BIM and the integration of quantity takeoff, location-based quantities, resources, productivity rates, and labor costs into the BIM, thus making the 4D BIM vastly more powerful and valuable to the Owner, CM, and the GC’s Preconstruction and Operations teams. We also automatically produce a cost and resource-loaded schedule from this workflow (to the delight of the Owner and his or her CM).
5D BIM: Recall that the 3D BIM is a collection of objects (which have their unique polygonal geometry from which we can extract construction-caliber quantities). These elements have what we call an assembly structure: the cost of the item, the cost of the crew to install it, the tools and materials necessary to install it, and its quantities per location. Pulled together, this produces a cost-loaded schedule for earned value analysis.
You should be able to compare cost plans to the original project budget at any point in time. Integrating this information back to the 3D model helps Owners understand which decisions have the largest impact on the budget. And all of a sudden, your 5D BIM model becomes the hub for each project decision, your go-to source for what-if questions, and a true reflection of your organization’s understanding of the project.
BIM-Based Production Control: Once you break ground on the site, you’ll want to check your progress, post look-ahead schedules, identify crews who are working slower or faster than planned, and make the appropriate adjustments. “Controlling” the schedule is critical to an organized and on-time completion of the project! The easiest way to remember this is that 2D is paper, 3D-4D-5D-PC BIM are all models. The models all look the same, it’s just that they are referencing different information from your knowledge base of cost and time elements along with your estimating database.
So the next time an Owner asks “Do you do BIM?” make sure the answer is a resounding YES!