IFC Common Property Sets

What is the most important thing in BIM? At least on this question everyone agrees - it's about that I, i.e. the information assigned to the components. In order to make this information in the openBIM process understandable for everyone, buildingSMART has also defined corresponding property sets in the IFC schema for each class, which describe the essential properties of this component. In this way it can be ensured that any software in which this IFC is read out will find these properties straight away.

These properties are defined as Common Property Sets and are also exported by default when exporting IFC from Revit. Please note:

Not all properties from the IFC schema are available in Revit by default! 

The reason for this is simple - many of these properties are probably only relevant for a few projects and having them by default in Revit would overwhelm the user.

But let's see this in detail using a wall as an example:

Link to current IFC 4 documentation

Here we can read exactly which properties are contained in the Pset_WallCommon. For the export it is important that the following option always remains activated:

Export of default properties in Revit

If we now export a wall from Revit, we notice the following:

This means that the following parameters are automatically mapped in the case of a wall:

Pset_WallCommon
ExtendToStructure = Top edge is fixed. (Yes No)
IsExternal = Function (External = Yes, Internal = No)
LoadBearing = Structure (Yes/No)
reference = type name
ThermalTransmittance = heat transfer coefficient (U)
FireRating - Missing
Combustible - missing
SurfaceSpreadOfFlame - absent
Complementation - missing
Status - missing

There are two ways to describe the missing parameters:

  • either parameters with exactly the same name and data type are created and filled in Revit
  • or values ​​of other Revit parameters are mapped to these parameters (requirement: the same data type)

Add IFC properties in Revit

In this case, it's easiest to use the shared parameter files that come with the Revit IFC plugin, since you don't have to worry about the data type in that case.

For Revit 2021 the following path applies:
C: \ Programdata \ Autodesk \ ApplicationPlugins \ IFC 2021.bundle \ Contents \ 2021 \ IFC shared parameters-revitifcbuiltin_all.txt

Notes:

  • Free choice between type and copy
  • Grouping is not critical, but IFC parameters are recommended for a better overview
  • Important: select the correct categories in the right window
  • The parameters MUST not necessarily be shared, but it is recommended as part of good BIM management

All IFC parameters that you create and fill in this way (attention, parameters with empty values ​​are not exported!) are also automatically added to the PSet_WallCommon.

Unfortunately, the disadvantage of this method is that you use terms like Fuel in your Revit project and thus the prerequisite is given that the employees understand all these terms and can assign them correctly. Therefore, in practice, the so-called parameter mapping is used.

Mapping of Revit properties to IFC properties

To map custom Revit properties to IFC properties, use a parameter mapping table - this is a simple text file with the following syntax:

A text file prepared in this way can then be selected in the IFC Exporter and causes the values ​​of the Revit properties to be transferred to the corresponding IFC values:

One final note: it is not intended to assign more properties than those already defined in the IFC schema to the standard property sets, as this would make them lose their universal character.
However, other properties can be defined in the form of your own, user-defined property sets – more on that in the next post!

0 comments
  1. Hello Lejla, with Revit ifc export, nested families, i.e. an assembly with several individual parts, are resolved and only the individual parts are displayed in ifc. The superordinate family with all information disappears in the ifc. I know that in Revit I can declare the individual parts as not shared but that would break my BOM in Revit. Is there a way to export such a Revit model to ifc so that the superordinate families appear in the ifc with all BIM information?
    gruß

  2. Hello Zeljko, unfortunately I don't know of any other way than the one you describe - although of course I can understand that this is not always desired in the Revit project itself. Anyway, it's an interesting question - I'll ask the development team!
    Greetings, Lejla

  3. Hey Leijla, your posts are really very helpful and have a very good quality in terms of content. Thank you very much for that!

    But I have a question regarding Revit and IFC.

    How can I define my own types for a component and export them under this name?

    Example: According to the IFC, wall has the predefined types: MOVABLE, PARAPET, ELEMENTEDWALL etc.. But I would like to define a type for the component via IfcExportType that is not available in the data structure.

    How do I do this in Revit?

    Regards
    Oguzhan

    1. Hello Oguzhan,
      Thank you for the nice comment, it's always nice to hear that someone is reading along and appreciating the content! 🙂
      Predefined types are defined in the IFC schema, and in your case you would have to use the predefined type USERDEFINED and then set the value via ObjectType - in the current IFC manual you can also find this on page 16 including screenshots - here is the link to the manual, if so you don't have it yet: https://www.autodesk.de/industry/bim/interoperability/ifc

      Best regards,
      Layla

  4. Hello Leijla,
    First of all, thank you for the interesting posts. I'm currently facing a problem for which I haven't found a solution yet. I created a shared parameter that I assigned to the Material category. So I can fill this parameter in the material browser. Unfortunately, I haven't managed to export it to an IFC file yet. Do you perhaps have a solution?

    Best regards,
    Julia

  5. Hello Lejla,
    first of all thank you for this section! She has been accompanying me for weeks with the introduction of BIM in my office.

    I have a question about the mapping of Specific Psets - e.g. on a wall. I would like to assign parameters like maintenance (true value), maintenance interval (positive integer), construction cost (positive number) to the components. The parameters exist in Revit and have a value. I'm exporting with custom property sets, in whose table I've entered the new parameters. However, they do not come out in my IFC viewer.
    Do you know what could be the reason?

    Kind regards,
    Antoni

  6. Hello Lejla!

    I have a question, we are only at the beginning and are currently taking the final steps towards BIM certification.

    My question would be how it works with non-standard parameters such as fire resistance, sound
    look like this exported.

    LG
    Julian

  7. Hello Lejla,

    to create a new IFC class? So an IfcElementProxy in any self-designed IFC class. Such as IfcBimMeUp?

    Thanks and best regards

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