Tuesday, September 01, 2009

Errors and Omissions

Every now and then I read an article pumping BIM or Revit. It used to be few and far between but new articles pop up daily lately. All too often the words, never, perfect, automatic, press-of-a-button and many more show up in the text. These words are used to compare Revit with other software and are often meant to highlight the strengths that Revit has. The fact that we can generate elevations and sections easily and that they are derived from the model without drawing them completely from scratch is wonderful. Many examples can use a little dose of reality.

There is an Urban Legend where a person bought a Winnebago and thought the cruise control didn't require someone behind the wheel. Most people laugh or at least chuckle at the notion that someone would set cruise control and get up to make a sandwich (the version I've heard, and believed too for awhile, the most) and think that the vehicle could safely navigate on its own.

Let's be clear...we can make mistakes in Revit too.

I used the image above a few days ago regarding interference detection but each of these things can be done easily in Revit.

Revit coordinates information much better and makes it more obvious that things are wrong too, like the things in the image. When things are working well, if it is correct it is correct everywhere. With Revit, when it is wrong, it is wrong EVERYWHERE too. This is an important distinction. When comparing Revit to other software the thing that is wrong in other software may be correct elsewhere because there is no connection to the other drawing or representation of the building. The distinction here is that documents are derived from the modeling process in Revit and embellished to create a finished document, with documents as the deliverable or focus for now.

Schedules are never wrong! I read this one every now and then, unfortunately this is incorrect. A schedule that does not use sorting/filtering, design options or phases as criteria will not report incorrect information. A schedule will NOT misrepresent data though. For example, a single panel door will not magically become a double panel door unless someone swaps a single for a double in the model. A schedule CAN misrepresent the whole story though by excluding information because of criteria applied by the user. User Error CAN and WILL creep into a Revit model. You can't blindly accept the results you get.

If we can make mistakes in cad and in Revit then what's the difference?

The difference is in how many of the mistakes are easily prevented or eliminated. Revit does a great job of managing the annotation related to views, sections, elevations, details and enlarged views etc. So much of the hassle of checking these is greatly reduced. When mistakes are made in Revit a team is much more likely to bump into them because they are working on the same data set or model. With the separate file process used by cad a team can be quite isolated from one another. How do I know if someone is making mistakes in their drawing if I really only see their work when it is printed out? Even then I have to visually compare their work with mine. Digitally I can reference their files and check them on the computer. All of this is so much easier, or at least more fluid, and we are always in the context of the building with Revit.

So much of quality assurance is the rigorous studying of printed drawings for inconsistencies. Much of it is based on years of experience and even intuition. I know that this and this are likely conflicts so I'm hunting for them. Most firms have checklists that go on for days.

It is my observation that teams using Revit know more about each others work and the whole building than teams who use other software. How can you avoid being more aware of what someone on your team has been up to when you see and walk by their work in the model each day? I've also observed many times that two users will have a conflict because they both observed a problem and set out to fix it at the nearly the same time, which generates a permission warning.

With my Revit bias you won't likely find me telling you Revit isn't the correct choice for you. I do want you to have realistic expectations though. The Staples EASY Button is a great fun thing to think of but what we do in this AEC business is rarely truly easy.

Mistakes can and will be made using Revit. Revit does give you a much better chance to catch and minimize mistakes as well as the opportunity to focus on making good decisions, and doing so as early as is practical so that the costs associated with those decisions can be managed well. Said another way, a past client once said to me in language more colorful than I'll write here, "My staff are making mistakes in cad all day long, at least in Revit they will be better coordinated!". Perhaps a bit too practical or not a lofty enough goal, but focused and realistic!

1 comment:

Christopher Hubbard said...


Missed this post earlier.

I must say that I agree with you, that Revit can assist with reduction in errors while Brand X does not have the tight constraints that control that.

One thing I wanted to note was we have been getting information fron the Insurance Industry (O&E) about concern with BIM and specifically Revit content created by non registered professionals that may not meet code and could contain errors that expose the firm to liability. I wanted to make sure people are careful about what they download and use even if it comes from a known source. There is still some real CRAP on Seek and Sweets.