Revit – Black holes on Level Four, the Vortex of Doom, Thinking like Revit, and Best Practices.

Revit – Black holes on Level Four, the Vortex of Doom, Thinking like Revit, and Best Practices.

A designer asked for help this week with a project where they were having difficulty creating shafts on certain levels. On some levels there was no issue, on other levels she was unable to create a shaft to save her life.  This was her question:

“Good morning! One of my revit models is giving me trouble when creating a shaft. When I choose to create a new shaft it immediately gives me an error that the top of the opening is lower than the bottom of the opening. It does not allow me to adjust the heights, and I am unable to place a new shaft. I’ve audited but cannot figure this one out…”

When I jumped into their model, activated one of the problem levels and launched the shaft tool, I was greeted with this dialog box just as she described it:

Invalid shaft settings
Invalid shaft settings

Clicking Delete Element(s) gave me another cryptic message about not being able to delete the element I am unable to create in the first place.

Can't delete currently active element while in sketch mode
Can’t delete currently active element while in sketch mode

Of course hitting the Cancel button will allow me to exit the sketch mode based shaft command, leaving me right where I started with no shaft!…. It seems my designer has spawned a black hole and now I’ve been swept into the vortex with her! So I try again and this time pay attention to the property palette.

Its a black hole or an inside out shaft...
Its a black hole or an inside out shaft…

Notice the level based constraints on the shaft and the resulting Unconnected Height. Seeing this, I switch to another level and try creating a shaft and viola no error message, I seem to be able to create the shaft with no problem. So it appears the black hole only exists on the fourth floor.

Remove the top constraint association - first!
Remove the top constraint association – first!

So I cancel the command and see if I can create a shaft on the offending level four again…much to my chagrin, I still cannot create it, but at least I’m not past the event horizon so I cancel the command again. My next thought is it is a problem with an existing shaft and prepare to find the offending shafts and remove them. But wait, before I go down that rabbit hole, let me think about how Revit works! I know that Revit is always trying to help me by remembering the values I previously used for different commands… so maybe all I have to do is successfully create a shaft that is not tied to an upper constraint.  As shown in the image above, with a floor to floor height of 20′-6″ (intermediate level not shown), a base offset of 15′-0″ the result is a shaft of 5′-6″, which is valid.  Then it occurs to me, perhaps I shouldn’t have canceled out of the command after all! Since canceling didn’t store the value in the properties palette, I go ahead and try creating a shaft again on the level without the black hole, this time setting the upper constraint to “Unconnected” and clicking the green check mark to successfully complete the process.

Click to finish the sketch and create the shaft
Click to finish the sketch and create the shaft

Completing the process results in new shaft tool defaults, so when I launch the tool on another level, the properties of the shaft tool will default with the base constraint of that current level, but no upper constraint. My theory is that the tool will not error out.

Unconnect the top constraint
Unconnect the top constraint

I try on another level and have success. I try on the offending level and have success.

Success!
Success!

Ding ding ding, winner winner, chicken dinner!

Once I’ve created a shaft I am able to then create a new one on any level I wish. So next time you’re faced with this vortex of doom, just find a level that works, or create a new level and create a shaft with no top constraint. Then you can delete it and resume creating shafts on levels you want to create them on.

The invalid default settings have been replaced.
The invalid default settings have been replaced.

P.S. I am sure that this problem originated as a result of nesting shafts within Model groups and copying them from level to level with “Upper Constraint” properties tied to levels.

Revit: Best Practice – Shaft Openings

So the best practices for today are:

  1. NEVER create elements with Upper constraints set to a level and then group and nest them and copy to other levels.
  2. ALWAYS remove the “Upper Constraint” for elements within Groups and set the upper constraint to “Unconnected” with an explicit height.
  3. Better yet, don’t include level constrained elements inside groups!