No Dimension Line? No Problem

Editor’s note: This post was originally published on EvolveLAB's blog and re-published here with permission.

Every so often, we come across BIM documentation that looks like this:

BIM- conduit-center-line.gif

The GIF above shows a conduit center line.  Many have had to use a detail line drawn through the center point of the conduit elbow to get the dimensions that they need.

The reason for this is that OOTB fitting families aren’t built with the references required to properly dimension the system.

Below is an example of adding a reference within the family to enable this dimensioning ability. It isn’t always more advantageous to add a reference line versus adding a reference plane for dimensioning, but in this case, adding a reference line makes the whole process much easier to adapt.

First, we’ll go ahead and open a conduit elbow family from the imperial library (any family can theoretically have this functionality added to it though).


Conduit Elbow Fitting from Imperial Library

Here I’ve navigated to the Reference Level Floor Plan view of the family:


What I’ll go ahead and do right away is add the reference line to the family and constrain one end of the line to the fitting’s arc center point.


Next, I’ll add an angle parameter that will allow the reference line to follow the fitting’s arc’s midpoint as the angle is changed.


Here is the Half Angle instance parameter that was created:


Last, I add the length parameter for the bend radius to the reference line, so that the end of the reference line will grow/shrink with the bend radius.


Now, we have a fully functional reference point to draw our dimensions. As we move our conduit in the project, the dimensions will follow, and we can achieve a BIM process where previously the process wasn’t delivered out of them box.


For automatic documentation workflows, we had to add some sort of visible geometry to the project when working with Revit 2017 and earlier. Revit 2018 API now allows us to grab all the references from the family (such as reference planes/lines) with one simple method ( This has already led to brilliantly streamlined documentation processing.

Feel free to reach out to Mark by visiting his blog here. You can also download the Conduit Family.

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