Project and Shared Parameters with Yes/No data type - issues with IFC export - Revit 2025.4
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I created a project parameter called 'IsExternal' and assiged it to 'Walls', clicked a few of them to mark them as external (IsExternal=True); Next, I created an IFC export script that relates the parameter to IfcWalls and exported an IFC file. The expected outcome was to have all walls that have been checked as external with 'Yes' and all unchecked with 'No' in the IFC file.
However, I am only getting an output for the parameter for walls that were marked as 'Yes' for 'IsExternal' while other walls do not contain the parameter. (See Picture 1 - parameter checked to suggest 'Yes' and Picture 2 - parameter unchecked and grey to suggest 'No').
The only way to get 'No' in the IFC file for the custom 'IsExternal' parameter is if I make sure the box is unchecked (See Picture 3 - box is first checked to activate it from being grey, then unchecked to appear empty).
I believe this is a bit illogical and more time consuming that it should be, why do I need to also uncheck the elements that require the parameter to be 'No' in order to have the parameter in the IFC export? It is much more practical to have unchecked and grey = negative. It adds to the workload if I have to check both external and internal walls one by one to make sure the export has all the information for the custom parameter.
I am using Autodesk Revit 2025.4.
Note: I am aware that this parameter is exported by default by taking the information for 'Function' for Wall elements, I just need it to be a custom parameter under a separate property set.
This post has been edited due to: @heather_tracy added the product and product version to the title to help more users find this topic via external search.
