Industry Foundation Classes (IFC) is the data format for OpenBIM and provides an interoperability solution between different software applications. With IFC is it possible to export 3D objects and their properties.
SketchUp has some issues with the original IFC export function. You can only export the Description and Name properties from the dynamic component. It’s also impossible to export custom property sets attached objects. I hope that SketchUp will improve their IFC import and export function to improve the BIM workflow.
After the general information about IFC and SketchUp, I will answer your questions now:
1: 2D lines and 2D objects without any face don’t export to IFC.
You must model objects with a face and it is important that the exterior of the modeled object consistently consists of the “front” face.
It is possible to export different 2D faces to IFC as you separate them in a group and give the groups different colors / materials. In Solibri it will appear as one solid but you see the different colors.
This is only a solution for visualization purpose.
Can I ask why you want to export 2D information in IFC?
To export 2D information you can export your model to a DWG or DXF file.
That is the open standard for 2D information.
2: For a proper IFC export you must give all the objects (dynamic components) a classification.
You can do this with the BIM Classifier function. With this function you tell what the object is, for example: Beam, Door, Roof etc…
If the object (dynamic component) has a classification, IFC properties will appear in the component options browser. Only the information from the Description and Name properties will export to IFC.
If you are interested in a BIM workflow with Sketchup, please look at the BIM Basis ILS in the Netherlands. It is an initiative to use a basic information delivery specification.
I hope this helps.