Problems with Groups, a brief look at the most abused tool in the Revit toolbox.

Using groups in Revit seems to be a no brainer; we create groups for elements that are repetitive and yet we are still be able to quantify them as if they were individual elements. Modify one instance of the group and it will be updated everywhere in the entire project. One can even exclude an element from a group instance to make an exception. Over the years, Autodesk has improved upon this awesome tool, but has not made it more flexible. If we create a group the wrong way, Revit gets upset. You don’t want to see Revit upset. In actuality, Revit actually gets confused. The main problems occur when groups contain elements that are constrained outside the group. In the simplest form, if one was to create a group of elements including a door, the wall where the door is hosted would need to be within that group. And in many instances the wall could have a top constraint that is not applicable for all instances. It is also common to create groups for casework that rely on the walls for placement, but the walls are not part of the group. In class, you may have heard me say, groups should be “self-centered”. These types of constrained can also cause problems in Design Options.

That being said, yes, there are restrictions that one should be aware of when implementing the use of groups throughout a big project. Here are some tips.

• Put elements and their hosts in the same group.
• Ensure all elements in the group are hosted to the same level.
  • Some elements may not behave correctly. Line based families for instance.
• Don’t constrain elements outside the group. There are many kinds of constraints.
• Large numbers of elements in a group will hinder performance, and possibly cause corruption.
• It is better to have many small groups than a few large groups.
• Don’t nest Groups. Don’t have groups inside groups.
• If you see a warning asking you to fix the groups, don’t. Fixing the group really doesn’t fix the group. It actually explodes it or creates a new group that is no longer referenced to the first group.
• Name groups correctly. Don’t make copies of groups called Group1.
• Although we are now able to mirror groups, some elements with constraints still cause problems when mirrored. Ceilings in groups get confused when mirrored.
• Take ownership of the group type workset when editing
  • All elements in a group reside on the group instance workset.
  • Be Aware of the ownership of type properties.
• Be cautious putting floor or stairs in groups. Don’t lock the sketch lines to other objects.
• Groups can be used to distribute elements and then can be un-grouped.

In a previous post, I discussed “What Causes Revit Data Corruption?” and some model maintenance suggestions, “Revit Project Maintenance Guidelines”. I hope you find this article and those listed here helpful. Reach out with questions or comments anytime.

Credits:

Best Practices with Revit Groups: Rule #1 http://www.seandburke.com/blog

About Best Practices for Groups Autodesk Knowledge Network