Base Quantities for Objects (2025)

[stefan]

There is a 2019 post with a similar subject, but I'm looking for a more general solution.

I'm setting up modelling conventions based on IFC and need to confirm if this also works inside Archicad.

Base Quantities for beams, columns and quite a few other Archicad categories are calculated automatically, when you active IFC Base Quantities in the IFC Translator. However, when using GDL objects, this doesn't seem to be the case.

E.g., when I use a "Beam" GDL Object, no quantities are exported (I did classify the object as a Beam so it becomes an IfcBeam upon export).

I added a custom IFC property named Qto_BeamBaseQuantities.NetVolume in the IFC project manager to the GDL Beam.

and also set a mapping rule inside the IFC Translator to map the default "volume (net)" to this IFC Quantity. 

And as a result, the Quantity is there in the IFC file...

Alas... this is not a real Quantity (IfcVolumeMeasure), but an IfcPropertySingleValue in the IFC file. So it only looks about right, but is semantically wrong...

At the same time, I assume that actual beams get properly calculated, so there is no reason to override this calculation based on my rule. What would be the correct approach? I don't want to recreate the full set of all IFC Base Quantities for all objects, based on the built-in quantities for Archicad objects, if they are already properly calculated for regular categories.

Are custom quantities properly supported in the Archicad IFC mappings and translators?

[davdelven]

This is something important, indeed. As long as there are more elements built from a GDL-object perspective, that could be an issue regarding the publication of QTO and Bill of Quantities based on openBIM approach from Archicad.