Get and Set Parameter - Error Parameter is Read only


I have a mass built in revit with a series of points (5 x 5 grid) I set a parameter to the Z offset to each reference point.

Revit screen capture





I got all the parameter values from my mass and port it to an excel file.

Get points






The values were changed in excel and the new values are ported back. But when I do this I get an error. Parameter is read only.








Is there a step I’m missing? It seems like a straight forward process but I’m doing something wrong.

Thanks for helping out.

Just a guess, but the problem might be that you are within the same transaction. If you put a Transaction.End node followed by a Transaction.Start node between the List.Join and the Set Parameter By Name nodes that might fix the problem.

The error message tells you exactly what is going on here: You’re trying to write to a read-only parameter. To filter out read-only parameters, you can use Clockwork’s Element.ParameterIsReadOnly node in conjunction with a List.FilterByBoolMask node.


You are right. the node you suggested came back all false. everything is read only.

My knowledge is very limited with Dynamo so I’m out of options. Can you suggest a workflow for what I am trying to do. I want to:

  • export the z offset parameter to excel
  • modify the z values
  • read the excel file and the revit model will then modify based on the new z values.
thank you for your help.


Once you have associated the “Offset” parameter with a family parameter, it automatically becomes a read only parameter.



At that point the only way to change it is to modify the family parameter you associated it with or to disassociate it.


I was afraid of that. ok, thank you!