buildingSMART Forums

How to recognize "earth connected" of ifcCovering or other Entities


we are a bit crazy in Switzerland to classify elements whether they are earth connected or not, because they might have different costs. Is there any relation to get the information of a ifcCovering (or ifcSlab/ifcWall) wheather it is connected to earth? When not, what is the recommended way to get this information of the user? a property or a custom system for all earth connected building elements?

Thanks for your hints or best practise hints,

I’ve never dealt with this issue, but here are some methods I can think of.

  • IfcSlab.PredefinedType = BASESLAB as “The slab is used to represent a floor slab against the ground (and thereby being a part of the foundation).
  • IfcWall.PredefinedType = RETAININGWALL as “A supporting wall used to protect against soil layers behind.
  • IfcCovering.CoversElements.RelatingBuildingElement. If RelatingBuildingElement = ( IfcSlab | IfcWall), then check if PredefinedType = ( BASESLAB | RETAININGWALL ).

I would not treat IfcCovering in a special way, instead an IfcCovering should always cover another element, and so you should resolve the root element, and then query that element.

Alternatively, perhaps “earth” can be considered as vital to the wall / slab / whatever’s construction. In that case, an IfcMaterialLayerSet can be applied where there is an IfcMaterialLayer.Category = Insulation. However, I find this semantically awkward, as it requires a thickness value (even if set to 0, it is strange for me).

Of course another easy alternative is a custom Pset, but I think this should be avoided if there is a more native way to do it.