Reductive Thinking in BIM: Autodesk Revit and the Myth of the Over-Modeled Family

Industry Talk

Revit and the myth of the over-modeled family

How did we get here?

Making buildings is complicated. There is no doubt about it. Every year, talk increases about how the construction industry is falling behind. The main problem with construction is that it is fractured. Everyone involved is a specialist and uses specialized software. This is why developers have focused on collaboration for the last decade. There are so many moving parts it is hard to keep track of what is what. It's easy to see why simplifying things would be necessary.

Reductive Thinking

As a new Revit user, one of the first things you learn is that file size is bad. It's black and white. Take a look at any Revit message board. The forums are littered with questions about reducing file size. This creates a tendency to think of our projects like laboratories. We need to maintain a clean workspace. Anything that increases the file size of our project contaminates our beautiful experiment. Revit tends to bring out the purist in us. It's not surprising that a reductive way of thinking started taking over how we make families. Revit is object-oriented — A wall is a wall, a floor is a floor, and so on. Objects need to work in a specific way so that we can collaborate across trades. This isn't the wild wild west like AutoCAD.
Yes, there are still workarounds. Yes, there are still loopholes. But in general, Revit rewards you for not faking things.


A few years ago I attended a case study lecture about a large healthcare project. They had developed a script to query the project for any placeable family over 500kb. Any family found to be over 500kb would have to be re-worked or replaced to come in below the threshold. I couldn't believe it. Where did this arbitrary number come from? For reference, Autodesk Seek's Revit Model Content Style Guide recommends doors and windows to be 600kb. This guide was published in 2009! The family templates that come with Revit are between 300-400 kb. This leaves you with 100-200 kb worth of size to create your family. It was at this moment that I realized that reductionist thinking had become a problem. As the wise Obi-Wan Kenobi once said, "Only a sith deals in absolutes."


Only a Sith Deals in Absolutes

The Smoking Gun

Building product manufacturers deserve some of the blame. The pressure was mounting for manufacturers to make their content in Revit. A 2012 report from McGraw Hill Construction illustrates this pressure. Lack of BIM content from manufacturers was cited as one of the largest problems for Revit users. Most firms did not have the resources to make large quantities of families on their own. After relentless pressure for content, manufacturers finally gave us what we wanted.

Or did they?

Manufacturers took the path of least resistance. First, they exported their manufacturing model to DWG. Then, they imported the DWG straight into a Revit family. Every bolt and screw is showing. 500 new line types have inadvertently been added to your project. The family isn't parametric and it contains no usable data. This is how the "over-modeled" family was born. We learned an important lesson. Trying to get manufacturers to adopt BIM with very little recourse to show ROI was going to be a tall order. This isn't something that you can do half-heartedly. You have to dive in headfirst. Remember how fun it was to convert AutoCAD users to Revit?

The overcorrection

Like an inexperienced motorist who hits a patch of ice, this led to a hard overcorrection. We call this the box dystopia. Instead of using the manufacturing model, BPMs outsourced their content creation. The creators made families with the smallest amount of detail possible. Because the families were outsourced, BPMs did not update or maintain any of their models.

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Kyle Bruxvoort