The Global ARCHICAD Community

Stay informed. Get help. Share your knowledge.

Everything about GDL - Doors/Windows/Objects/Stairs etc. (Example: I created an object that prints an error message in 3D all the time, please help!)

Moderators: Barry Kelly, Karl Ottenstein, LaszloNagy, ejrolon, gkmethy, Gergely Feher

In the standard ArchiCAD Library, some objects have preset Classifications, while others are unclassified. For example, the Precast Beam objects are set as a Beam in the Classification system.

See attached screenshot.

I know that it is possible to change this on the fly for any object, however I am sharing some project files that have been migrated into AC21 and want to make sure that I have preset both standard and custom library parts properly in terms of classifications.

I opened up the Library Part editor and assumed it would be set in much the same way that you can set default parameters, but can’t see any information about classifications there.

I also looked in the GDL Reference manual and can’t see any info about where this is set.
Just quickly (because I have to go and can't test) - does it come from the object sub-type in the GDL editor?

Hey Barry - I looked at object subtypes and didn't see anything that defined or selected a classification. I used the command Open Object by Subtype and selected Beam (for example) and it looks just like a normal object except for the checkbox in the Details section that says "Use as subtype". There's nothing that I can see that refers to a classification.

As an extra test, I saved a Precast Beam object as a new Object in the Embedded Library, and changed the subtype to Column. When I opened up the Object Settings, this new object still knew that it was a Beam; it did not change to be classified as a Column, so it was not affected by the Subtype.

BTW, when I search for and choose an object that is clearly a column, for example Column Doric 01 21, it has the classification Column as expected. So there MUST be something in the library part definition that remembers the classification, I just can't see it...
Update - it appears that the subtype does control the new object. At first, when I opened up the object settings for the new beam object that I set to use the Column subtype, it still showed Beam as the classification. However after I switched the object settings and selected other elements, then came back to this new object, it "correctly" showed Column (matching the arbitrary subtype I had chosen).

I did some more web research and found some references to this in the IFC documentation: ... _ifc_data/

Here is a relevant excerpt:

In the case of Objects, if it has a Subtype (for example, an Object having a Column-subtype), that subtype will map the Element Classification and thus the IFC Type. For example: “Column” Subtype sets “Column” Element Classification and thus “IfcColumn” IFC Type.

The article refers to "default Subtype-Element Classification mapping" but doesn't say where this is controlled, or even if there is a mapping table that can be viewed or printed.

I found one more reference to this system in the following document: ... m/63135-2/

I haven't seen anything based on AC21, so I don't know if there are any changes with the advent of the Classification Manager and the additional options for multiple classifications to meet different standards.
Hello Eric,

In ARCHICAD 20 you only had the Hard-wired Classifications of ARCHICAD 20, you couldn't choose the classification of the elements freely. In that system objects were special, as not every object can be classified as furniture, there are quite a few appliances, building structures, MEP Elements, etc.. To solve this conundrum we wired the classification to the subtype of the object.

In ARCHICAD 21 this system changed: Now you can create your own classifications, and select the classification of each element freely (you can even have multiple classification systems for each element). In this new system we couldn't tell what to set as default for elements (since we can't know what kind of classifications will one use), so we gave that choice to the user: you can set up the Default/Favorite of an element with a specific classification. When you open a tool in ARCHICAD 21, and you see it is already classified as a "Wall" by default, that's because the default of the wall in the template was saved like that. If you change it to something else, it will have that as the default from that point on.

Still, in this system we had to make sure that objects get classified properly by default/template. The way we did that is (similarly to general building elements) it will just save a default in the PLN/Template for the objects as well, but it will link this to the subtype. So if you open the default settings of a chair for example (which would be classified as a "Furniture" by subtype), change it's classification to "Wall", and click OK on these settings, from that point on, the default for the "Seating" subtype will be "Wall". This means, if you open the default settings again, and switch to a different element (eg. a Building Structure), and switch back to a different chair, it will be classified as a "Wall" by default.

I hope I could explain it well.
Hello dkovacs,

I understand that user defined classifications is also the reason why only the Source Classifications System for Archicad Classification is properly mapped to IFC types.
We are implementing the UniFormat classification and I am looking for a solution to avoid multiple classification for each element. For now, only Archicad Classification is properly linked to the Property manager and connected to the IFC types for Export .

Do you think it is possible to re-map UniFormat (also other mainstream classifications) by connecting the properties in the Property Manager and IFC types for Export ?