why bim?

The short answer: using BIM will save the project team time and money, and prevent a lot of headaches.

The long answer: there are many benefits associated with the use of BIM. Those benefits are realized incremently, as the various dimensions are implemented.

After the 3D model is created, the following benefits can be realized:
  • Increased visualization
  • Scope clarification
  • Document coordination
  • Collision detection and resolution
  • Options analysis
  • Building walk-throughs
After the construction schedule is linked with the model, the follow benefits can be realized:
  • Visual sequencing (increasing the realism of the schedule)
  • Visual logistics planning
  • Visual progress tracking
Finally, when the model is used to develop the construction cost, the following benefits can be realized:
  • Accurate cost engineering (instead of a cost estimate)
  • 'On the fly' value engineering
All of those benefits contribute to cost and time savings for both the designer and contractor. Proof to follow.

shortcomings of revit for contractors

We (the "BIM Team" at Tocci Building Companies) were just given a presentation by Hunter Marston, of Autodesk Consulting. Hunter showed us a Revit add-on tool that facilitates scheduling. As amazing as the presentation was, it really surprised us that this tool isn't part of Revit. In fact, Revit doesn't even have plans to include it in Revit 10.0.

Revit 9.0 has limited tools for contractors; the construction tab of the design bar gives 3 options:
  • Site Components, where you can insert trailers, cranes and other logistics components
  • Phases, where you can add phases to the model and customize phase filters
  • Schedule/Quantity, where you can create quantity takeoffs
Compare those 3 options to the structural tab (which has 12 options) or the rendering tab (15 options) - keep in mind that Revit has other programs which can do advance structural modeling (Revit Structure) and high quality rendering (3D Studio Max). Also keep in mind that the construction tools that exist are limited; phasing is cumbersome and time consuming, site components are not entirely parametric (try putting a temporary fence around a site) and quantity takeoffs sometimes do not include important parameters (try calculating steel tonnage).

How does Revit expect to compete with Constructor, a BIM tool that currently does everything? There are obvious advantages to using Revit - you don't have to give up your current software systems, like Timberline and Primavera. Also, it is an Autodesk product & Autodesk AutoCAD is the most widely used 2D CAD software in the US. By using Autodesk Revit, we are easing collaboration with all AutoCAD architects and users. However, as we continue to implement BIM using Revit, we are getting frustrated by the limitations of the software.

I implore everyone who is either using Revit (despite its current limitations) or interested in implementing BIM (utilizing Revit), to contact their Autodesk reseller (or me) with their comments regarding the limitations of Revit as well as their own "Revit wish list". I plan on compiling my own "Revit wish list" (as I've seen on other BIM/Revit Blogs) and will be contacting the Revit product manager with our comments.

Revit Wish List
  • A more intuitive phasing tool, that allows the user to set start and end dates, instead of merely naming a phase
  • A phasing tool bar, with a drop down box for changing the phase filter of the current view
  • More detailed phasing, so that the layers of walls can be phased separately and window openings phased the same as the walls they are in (with the window scheduled at a later phase)
  • All object parameters should be available for schedules
  • More parametric logistics objects (i.e. temp fencing) and a wider variety of logistics objects
  • More API tool inclusions, so that team members who are less familiar with Revit can contribute to the model (i.e. the schedule tool that can be exported to Primavera or MSProject and then imported back into the Revit model

Don't get me wrong; I love Revit and couldn't imagine a better BIM software to use. I only criticize out of love.

definition and dimension

The official term was coined by Jerry Laiserin, but there are as many definitions for BIM as there are people who are talking about it (but probably not using it). The definition that I prefer (and that we use at Tis the following:

BIM is an object-oriented building development tool that utilizes 5-D modeling concepts, information technology and software interoperability to design, construct and operate a building project, as well as communicate its details.

This definition considers the 3rd dimension space, the 4th dimension time and the 5th cost. Some definitions categorize BIM as 4D: the 3rd dimension is space and the 4th is the database of information that is available in the model. Other definitions (like the C3T definition) refer to the extended applications of the 3D model as "XD" since there are so many ways to utilize the model.

Personally, I like the 4D/5D method because it differentiates the uses of the 3D model, especially since most of the current applications relate to cost or time, or some combination of the two.

I consider any activity that relates to the spacial relationships in the model to be 3D: the development of the model, document coordination, the clash report, etc. The same goes for 4D and 5D; each dimension refers to a number of activities. In the future, I'm sure I will have to modify my definition to include 6D (procurement applications) and 7D (operations applications) activities. Until then, I'll leave my definition as is.

why I'm adding to the mass of BIM information

I'm aware that there are already tons of blogs (as well as other resources) out there that discuss BIM (building information modeling) and related practices. However, those resources are unintentionally one-sided; they are produced by the AIA and other architects. This is not to say that they aren't useful; I use these resources daily (in fact, I urge you check out the links to my favorite blogs).

However, as a BIM implementer at a CM firm, I'd like to offer another one-sided resource - but the other side.