Order of Materials in walls
Hi,
I built a wall with different materials (as IfcMaterialLayerSet) and now I'm wondering in which order I have to arrange them. Is there a general order in which I have to put them, for example start with the most inner/outer material? Here is one example of my wall construction:
Thank you! :)
Comments
The convention is that the 1st material in the list is on the exterior, and the last material on the list, on the interior.
I just added the following to the UI, to help...

Great, thank you!!
Hey @theoryshaw, I am interested in finding out if this is an Ifc convention or a user convention? I'm not sure how this can be applicable in all situations - what about interior partition walls that don't have a finished exterior material?
Our office uses a conditional convention for ordering wall assembly materials, prioritizing exterior, interior, or control line layers based on availability. If a finished exterior material is specified, layers start from the exterior (e.g., cladding material). Without an exterior material, layers start from the interior (e.g., plasterboard/gypsum wallboard). If the wall is an interior partition and symmetrical, it doesn't matter. Suppose neither finished material is specified or the wall is an interior partition that is not symmetrical. In that case, layers start from the preferred control line (e.g., consider if the wall were to change dimension slightly, which line should not change).
We found this convention worked for projects that contained complete IfcWall assemblies as well as wall assemblies that are a combination of IfcWalls and IfcCoverings. But in the end, it was not about BIM accuracy, but rather an office preference for consistency.
This is a user convention. IFC does not define interior or exterior. That said, we should as a community try to encourage a convention as a best practice so that we can share libraries.