What Revit Wants

Let’s say you have a nested family with a formula driven parameter, something like =Length/10. You want to expose this to a host family and make it a Reporting Parameter, but that option seems to be grayed out (firstly, because its formula driven, secondly because its a nested family):

Here’s what to do:

1. Remove the formula from the nested family and reload it (so you can now apply a parameter to it in the host)
2. Add an instance parameter as per the image above
3. Close this dialog by clicking OK
4. Go to the Family Types dialog
5. Select and Modify that parameter
6. Now you can tick the Reporting box
7. Edit the nested family again – reinstate the formula
8. Reload the family
9. You now have a Reporting parameter in the host family that tells you the value of a nested, formula driven parameter

Another workaround that may assist with reporting parameter restrictions is to:

1. Save the family and close it
2. Rename with extension .rft
3. Make a new family based on this “template”
4. Maybe the problems you were having with Reporting parameter restrictions are gone, but you might have mixed results