Reference Lines and a Former US Secretary of Defense

Reference Lines and a Former US Secretary of Defense

Put aside your political views and your opinions on the War on Iraq. We are about to get some BIM advice from Donald Rumsfeld.

[T]here are known knowns; there are things we know that we know.
There are known unknowns; that is to say there are things that, we now know we don’t know.
But there are also unknown unknowns – there are things we do not know, we don’t know.

United States Secretary of Defense, Donald Rumsfeld

I know there are arguments for and against it, but I’ll be honest… I LOVE this quote. And I really enjoy that it is from such a divisive figure as Donald Rumsfeld. I reference this concept almost every time I’m teaching a new student ArchiCAD.

Here’s why you need to respect Rumsfeld’s BIM advice.

When SALA Architects was transitioning to ArchiCAD, a regular complaint I heard from project architects went something like this: “the young staff are asking for information before I know the answers!” The crux of this argument was two-fold. First – designers were frustrated that during schematic design, the support staff wanted to know about wall construction, floor height, and other tectonic issues that weren’t necessarily asked for when working in other programs and methods. The project architect would get nervous and fear the design was getting pigeon-holed or pin-downed too early. Where’s the fluidity, grace, and magic? From this sprung the second issue. Working with ArchiCAD, the more experienced architects – the ones with a set process and an understanding of the traditional steps that lead to project completion – were forced to confront new, more advanced methods of working. The amount of time and fee you spend at the beginning of a project can be scary if you don’t understand the whole process (these two graphs will help).

BIM changes the order of things. It’s a paradigm shift.

What is to be done? What is the solution? It’s time to start thinking about Donald Rumsfeld. The question we ArchiCAD users are asking is what are the “known knowns” and what are the “known unknowns”. It’s okay not to have all the answers figured out. With smart modeling in ArchiCAD, we don’t need a final answer. But to be efficient and smart, we do need an answer. And ‘I don’t know, so let’s make an educated assumption’ is a perfectly acceptable answer. In fact, it’s a better answer than ‘go away’, ‘don’t worry about it’ or some overly specific seemingly concrete, but 100% wrong answer (i.e., treating a known unknown as a known known). In early design, ArchiCAD and BIM make us filter decisions into knowns and unknowns. Once they are categorized, we can start parsing them further. Because of codes, site constraints, design predilections, etc. a starting point exists for all these hyper-specific questions that get asked early. And if we have a baseline, then we can proceed with wisdom. Here’s a practical example:

ArchiCADReference lines. When first placing a wall during schematic design, think about the future. Is the reference line on the exterior of your building or the interior? If the wall grows, which direction will it grow? Typically projects have a suggested direction of growth. Perhaps it’s an existing wall that you don’t want to have to refinish on the interior. The wall has to grow out. Or maybe you’re building up to a setback or lot line. The wall has to grow in. There are going to be plenty of unknowns, but many of those unknowns are knowable and are things you can state clearly and place in the model with flexibility.

More about Reference Lines. I recommend adding the Wall Extras as a Sticky popup menu to one of your toolbars. The Wall Extras menu has three options: Modify Wall Structure, Modify Wall Reference Line, and Invert Direction. The Modify Wall Structure option is great for resizing walls from a constant point, for instance the middle or edge of the core (i.e., your known known from which the known unknown will occur). Modify Wall Reference Line is wonderful for flipping the reference line from one side of a wall to the other (though there are other options). It is great if you know which way the wall needs to grow, but sometimes you make an incorrect initial assumption. Modify Wall Reference Line will help you in these situations. And there are always unknown unknowns because clients have evolving issues, and bosses sometimes don’t give the production staff all the information they need from day one.

The Wall Extras menu provides the flexibility you need to work fast, efficiently, and yet still be able to resolve wall issues on the fly. It’s just one small example of using the tools within ArchiCAD to manage your known knowns and your known unknowns, and also to prepare for the inevitable unknown unknowns. Want to learn more about Wall Extras and reference lines? Here’s some old advice from an ArchiCAD Master that’s still relevant after all these years. Tired of reading for now? Here’s a video I did back in January 2012 that explains much more about all three options in the Wall Extras Menu.

This is all About Fighting Ignorance

All this talk about knowns and unknowns aims to focus the entire team on awareness of the design and documentation process. Mixing up known knowns and known unknowns is dangerous and leads to stifled designs and huge amounts of damage control. So the next time you are doing a schematic and come across a question, ask your team members “is this a known known or an known unknown?” You’ll be surprised how such a convoluted use of the English language will clarify so much.

um… how about some disclaimer language… Donald Rumsfeld wasn’t really talking about ArchiCAD or BIM.


  1. Guest Blogger James Badcock: Modify Reference Line in ArchiCAD 17 - [...] the reference line is so important in ArchiCAD, for wall stretching, clean up and editing, we weren’t able to…
  2. Compatibility notes: ArchiCAD on Mac OS X Yosemite (10.10) - […] than no BIMx there seems to be no known big problems. But there is a big difference between the…

Submit a Comment

Your email address will not be published. Required fields are marked *