Creating Revit Parameters to use with Groups and PropertyWizard

If you are creating parameters in projects that have Groups, and you are using PropertyWizard, you should be aware of this setting in the Parameter Properties dialog:

Revit Parameter Properties dialog, highlighting the group settings

What does the setting do? Well, it only has an effect if you’re using groups, and it’s only active for instance parameters. For example, imagine you add a new instance parameter to the Doors category. Each door in your project now has the new parameter, and since it’s an instance parameter you can set the value differently on every door.

But what happens if you create a Group, add a door to it, and then place several instances of the group? Can you still change all the parameter values independently?

That depends on this setting.

Group Settings from Revit Parameter Properties dialog

If you chose the first option ‘Values are aligned per group type’, then the doors will have the same parameter value in all the group instances – and you can only edit the value in Group Edit mode.

On the other hand, if you chose the second option, you can still freely edit the parameter values on each of the doors – you’re not restricted when they are part of a group.

How does this affect your PropertyWizard formulas?

This matters because PropertyWizard cannot enter Group Edit mode to edit parameter values. So if you choose the first option for your parameter, add some of the relevant elements to groups, and then try to drive the parameter with PropertyWizard, you will get a ‘editing while not in group edit mode’ error:

Revit Warning dialog showing a 'Changes to groups are only allowed in group edit mode' error

This error dialog cannot be bypassed or ignored – it only has a Cancel button. So it will stop and undo whatever you are doing. Which can be awkward.

So you have to use the second option ‘Values can vary by group instance’ for all parameters that you want to control with PropertyWizard.

A Few Awkward Types of Parameter

You will notice that the setting is sometimes greyed out, even for some Instance parameters. Why is this?

Well, for some reason Autodesk have chosen to lock the setting to the first option for these values of ‘Type of Parameter’:

Type of Parameter dropdown from the Parameter Properties dialog, highlighting the values that lock the group settings - which are: Integer, Angle, Length, Number, Slope, Yes/No, and Family Type

It is only locked for these few types of parameter in the ‘Common’ discipline, and not for any of the types in the ‘Structural’, ‘HVAC’, ‘Electrical’, etc. disciplines. It is unfortunate that the affected types include some of the most-used types of parameter in PropertyWizard.

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