IFC Export Issues - Openings and Generic Models Voids

[JasonLLINDNER]

Greetings Experts

The problem is with the model in place and generic model families with nested void extrusions that I used to cut a slab or wall openings (also any family modeled using a void extrusion insted default opening tool  to cut it's host) Every time I try to export as IFC it comes out as a solid block mass/extrusion when I link the IFC file back to a Revit model!! I have tried to change the IFC options and IFC classnames maybe a bit over 50 different combinations between Ifcbuildingproxies and ifcopening and Ifcvoid and and and No Use! same result

I am having same issue with some default windows and doors families...once exported to IFC they are filled with a generic mass/solid block instead of the opening! AND Same issue with openings done with Shaft tool...where the slab is supposed to be cut I would find the cut piece filling the void. (And of course all generic families with nested Void extrusion cut

1. if IFC format recognize voids and openings how are those handeled?
2. Is there a standard IFC Classname and IFC Mapping  definitions which covers all elements? (in the default file lots of elements are noted Not Exported) or building proxies)

Thanks

At the back is a generic model for elevator shaft with a nested void to cut slabs through all floors

Front is just a slab cut using the default Opening > Shaft tool

[Anonymous]

IFC is great to share a Revit model with other programs.  Not so great bringing an IFC model back into Revit.

Is there a reason you are exporting the IFC only to link it back into Revit?  Perhaps there is a different solution?

[JasonLLINDNER]

Hi @Anonymous

I took it as an elective for extra credits! Thought it will be an easy catch but it turned out that part of the kurss is to alanyse and understand how Revit works and not just tutorials to follow like those one finds online. So with each assignment there need to be a report with pros and cons associated with What IF(s) and Why NOT(s).

The IF for this one came out as: What if one can assossiate the generic model void cut and shaft openings with the IFC Classname and/or IFC Mapping definitions of the built in Revit Window families which actually work fine when exported (no mass/block filling the opening)

And I got stuck at this...howcome some built in window openings export fine and why can't one implement the same for other openings such as the ones I have stated above. At first I thought it has to do with Room/Space bounding requirements. I deleted the rooms from the model but that made no difference. I went through the whole Help Section (litrally cover to cover) checked several other forums and couldn't really find the logic so I thought maybe someone knows.

[RDAOU · Accepted solution]

Hey @JasonLLINDNER

1. Yes; IFC does recognize Voids and Openings (each differently)
2. Yes; there are standard IFC Class definitions for the different IFC formats (the ones listed in Revit Export dialog are not all... you can find a list with clarifications on  IFC2x3 Class Definition HERE

The best practice is trial and error till you find the configuration that suits/defines your project.

Example: gary slab cuts pieces added back after export to IFC.

1. They are still cuts...IFC export did not patch the slab
2. you can select those elements and hide them (visibility issue)
3. You might not find them nice (visually speaking) but others might find them essential
4. It's a Data model so everything is in it even the elements you subtracted (if you think about it; its how the volume of your slab is calculated for instance it's A-B = C...the gray part you see is the B

[Anonymous]

Hello,

I'm running in to a similar problem. We are a manufacturer of aerated concrete panels and silicate blocks and make all our drawings custom to the demands of the client.
Since a while now we are implementing bim and using ifc to import into our software for production.
First I thought it was due to our software some openings were not imported. But when I started reviewing the ifc's (exported by our clients) in other programs such as Tekla and Solibri it quickly became clear something is going wrong with the export.
The same errors occur when viewing the ifc's in different software packages.
Sometimes the voids only appear in the insulation and finishing layers, sometimes in all layers and sometimes in none.

Why does a particular type of window export as void in one wall and not in others even when the same types were used for both walls and windows?

It seems the problem especially occurs when walls are split into parts. Does anyone have some advice I can share with our clients on how to export correctly, so the walls geometry gets exported correctly including all the voids?