Voids not exported to IFC

[j-davelaar]

Good day,

When exporting my Revit family to IFC, I notice that some voids of the nested families dissapear.

This is a Revit model with the big steel cage family, but also similar instances of the nested family next to the cage in the project. Can anyone explain me why the voids of the plates are not exported?

(IFC files cannot be uploaded?? So the export has to be done manually)

[gokcen.ezgi.sen]

Hello @j-davelaar ,

I have reviewed your work, since you are working on a nested family, you cannot detect and define the void elements individually in the holistic structure of the family during the IFC export process.

For this reason, spaces can be exported as unidentified elements (other).

You worked on a generic model family and created voids with solid objects defined in the Invisible Family Subcategory. Even when you define void elements as void, you will not be able to obtain void elements defined in the IFC export process, since you are working in a Generic Model family.

In this context, I can recommend you to regenerate your model in a more defined way (except for the Generic Model).

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Best regards,

Gokcen Ezgi Sen

MSc. Architect - BIM Consultant

LinkedIn 

[j-davelaar]

Hello,

Have you exported the Revit file to IFC and have you seen that the nested families, placed as instance do get their holes, but the plates do not have holes when nested in the big cage family?

I have tried to change the category of the cage from generic model to structural column, but this did not fix the problem.

Did I do something wrong (or understand you wrong)?

[FuldenYilmaz]

@j-davelaar  when the model is analyzed, the cage is a generic model family therefore normally, void classes are not created from real voids. Your models include a void geometry like a nested family. Therefore the voids are not identified as "Void" in IFC. 

In fact, I think you should model a  cage as rvt model by using floor- and vertical voids.

[gokcen.ezgi.sen]

Hi @j-davelaar ,

Yes, I exported the model as IFC and even confirmed the existence of voids when I opened the file in a different software that allows viewing IFC files. You can see it in the attached image.

But these elements are not defined as void elements in the IFC model, they are defined as other.

Best regards,

Gokcen Ezgi Sen

MSc. Architect - BIM Consultant

LinkedIn 

[j-davelaar]

Hello!

Interesting to see that these voids do not get recognised as voids when working with a generic model. I do wonder how to fix this or if this is an IFC issue. I cannot make the cage family out of floors, because it has to be a premade loadable family. Floors are not loadable families.

Even if I change the category to something else than generic model for the host family, the voids do not appear in IFC.

I have also tried to add a normal void family (not nested profile) to the plates, but no succes in the IFC export.

Any practical tips on how to make the voids appear as voids in IFC?

[L.Maas]

Maybe you can try to do the following (I have not tested this).

Add the following to you void generic model void family

It might be needed to make your void family shared.

[j-davelaar]

Hello 🙂

Currently I have 2 types of voids in the lowest family. A void (default void function) which cuts the extrusion and a sweep (default sweep function) with a profile, which cuts the extrusion.

For both I cannot add a parameter, only for the profile. I have tried to do the IfcExportAs on IfcOpeningElement and I have tried the IfcExportAs with IfcBuildingElementProxy, but both didn't have any positive effects. What I do find strange, is that some other voids from the beams do not dissapear. I do not understand the pattern yet.

[j-davelaar]

Is there anybody who has an idea to practially fix this? All theoretical options didn't seem to work out!