Hey,
Here’s a forum result…
So, a key principle is that the surface used to create the Wall.ByFace must have a Revit ‘Reference’.
This is only created by Revit once the surface creation transaction is completed.
That’s why you see a ‘Transaction.End’ node in the example graph, it forces the graph to execute as 2 transactions rather than the typical 1 transaction.
When the 2nd transaction starts, the surface exists in Revit and now has a Reference which can be used to create the wall.
Hope that makes sense!
Mark