Adding Purlins to a Revit model can be a bit tedious as there is no “dedicated” function that specifically allows you to easily modify related parameters. In Revit you will need to make use of the Beam System function, AND you need to have a Purlin Family loaded before making use of the function.

Once selected, you will need to set the Workplane as the top flange of the Rafters and define to boundary of the Beam System, which is the entire one-side of the Rafters.

Once defined, you will need to change the z-Justification for every Purlin (you can Select Similar, etc.) to Bottom so that the bottom flange of the Purlin is resting on the top flange of the Rafter. If you aren’t happy with the number of Purlins, you can select the boundary of the Beam System and adjust the spacing.

Lastly, you will need to extend the Rafter ends so that their ends rest on the first and last Rafters. This cannot be done (as far as I have seen) with the Trim/Extend function. You will need to make use of the Change Reference function when selecting an element. This function works well in the relevant Elevation views.

Advance Steel, as with Portal Frames, has a dedicated function, called Purlins. This function is located in the Extended Modeling section of the Home tab ribbon.

Once selected, you need only select the relevant Rafters, press Enter, and select No for both pop-ups, after which a dedicated dialogue window will pop up which allows you to modify a series of relevant parameters.

This functionality really stands out for me as it would be very difficult to replicate in Revit.

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