In practice, foundations are often modeled with the wall tool. In principle, there is nothing wrong with this, but caution is required with the IFC export.
As you may already know from the Revit IFC Manual walls can also be exported as IfcFooting. IfcFooting is the corresponding IFC class for foundations.
All that is required is a IfcExportAs parameter (as a type or copy) and filled with the value IfcFooting.
What must be taken into account, however, is the function of the wall - it must be Foundation or Retaining wall otherwise the wall will be exported as a wall despite this setting!
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