Manually Specifying IFC GUIDs for Levels
The algorithm employed byRevit to create IFC Level GUIDS changed between Revit versions 2009 and 2010. This means the Level GUIDs created by Revit 2009 for export in a 2009 IFC file will not match those created for IFC export by a later version of Revit. If you need later versions of Revit to match the building storey level GUIDs created by Revit 2009, there is a simple way to do it:
- Open the 2009 IFC file in a text editor such as Notepad or WordPad.
- Search the file for all the strings “IfcBuildingStorey”. These lines contain the GUID for the levels. For example, in the line below, the level GUID would be 011Qw9l0H8eOB6Sxs85DRd.
- Copy each of those lines to a convenient place such as Notepad.
- Open the IFC file in the newer version of Revit.
- Create a new shared instance parameter in the project. Call it IfcGUID and associate it with Levels. See Shared Parametersand Specifying IFC Entities for Families.
- For each level in the project, paste the appropriate GUID value into the IfcGUID parameter in the Properties Palette. (Don’t include the quotes.)
- Save the RVT file.
- Export it to IFC again.
- You can then confirm that the building storey level GUIDs exported to IFC from the later version of Revit continue to match that which was exported by Revit 2009. We do not anticipate a need to change the GUID calculation algorithm in the future.