IFC Element Types

Each ArchiCAD modeling element, building-type object and annotation element has a mapped pair in the IFC structure (IFC element type). The following table summarizes the default IFC element types converted from the ArchiCAD elements.

Notes:

•The export of Grid elements and 2D elements occurs only if the appropriate option in the IFC Translator is enabled.

See Import/Export Filter Options.

•The IFC standard does not support the intelligent export of dimensions. Therefore, exporting dimension elements will result in these elements falling apart into lines and texts (IfcAnnotation elements).

•In the case of Objects, if you can classify a Subtype (for example, an Object having a Wall-subtype), then the object will be exported accordingly (e.g. as an IfcWall). Certain subtypes are automatically assigned the IFC element types that correspond to their group name (e.g., in case of the “Bed,” “Seating” or “Table” subtypes, its IFC type is automatically set to “IfcFurnishingElement”, since its group name is the “Furnishing” subtype). If no subtype exists that corresponds to an IFC element type, then we recommend that you search for a subtype under IFC2x_Base_Object (see illustration below), or use the “Element Classification” option in the Tags and Categories panel of Object Settings (see later). If no such IFC element type exists, then the Object will be exported as a general solid object “IfcBuildingElementProxy”).

An ArchiCAD’s element classification affects that element’s IFC export type. The mapping displayed in the above table shows the default and recommended situation, when an element’s element classification value (set under “Element Classification” in the Tags and Categories Panel of element Settings) is set to “ArchiCAD Type”.

The sub-elements that compose a Curtain Wall cannot be assigned an Element Classification. The IFC element types of all Curtain Wall Frames will be IfcMembers, and all Curtain Wall Panels will be IfcPlates.

But in some cases, you will have to model building elements that have no exact counterpart in the ArchiCAD toolbox; you will have to use an existing tool. For example, you might use the Slab tool to model a ceiling. Using the default “ArchiCAD Type” value for this element would export it as IfcSlab, respectively. To avoid this, use ArchiCAD’s Element Classification feature to handle these non-standard modeling and export tasks correctly. Except for ArchiCAD Zone, Grid and annotation elements, all ArchiCAD elements can be classified for IFC export purposes, so, for example, your ceiling modeled with the Slab tool can be classified as “Ceiling”. This way, that Slab will be classified as an IfcCovering element of the Ceiling predefined type in the IFC hierarchy of the architectural model (these settings can be confirmed using IFC Manager), as well as in the IFC model that will be exported.

See also IFC Manager.

Notes:

•Do not change an ArchiCAD element’s default classification unless your modeling logic requires such a change. In every other case, use the default “ArchiCAD Type” classification. For example, there is no reason to classify an ArchiCAD Wall as a “Wall”: this would produce the same result as retaining the default value of “ArchiCAD Type”, which automatically exports your wall as an ifcWall.

•Element Classification has another advantage, not directly related to IFC exchange: you can use Find & Select to filter the project by “Element Classification” criteria, or use Interactive Element Schedule to list this data for ArchiCAD elements. For example, you can select or list just the slabs that were used to model ceilings.

•Thus, Element Classification is an ArchiCAD-based classification function that affects IFC export. The available Element Classification values do not correspond exactly to the IFC entity type names. For example, the “Ceiling” classification: there is no such thing as an IfcCeiling; instead, the corresponding name is IfcCovering, with a predefined type of “Ceiling”. The same is true for the Roof classification: such ArchiCAD elements are exported as the predefined IfcSlab type. (An entity called “IfcRoof” does exist, but that is an IFC Container. See IFC Container.) To check the corresponding IFC Entity of any ArchiCAD element’s classification, check the “IFC Type” entity on the Tags and Categories panel of the element’s Settings dialog box or in the IFC Manager above the element’s IFC Attributes. You can also use Find & Select to filter the project by “IFC Type” criteria, or use Interactive Element Schedule to list this data for ArchiCAD elements. For example, you can select or list just the IfcSlab-classified model elements.

•An ArchiCAD element classified as Site Geometry will become, as part of the IFC export process, part of the IfcSite geometry (provided that the ArchiCAD element has a geometry). Since the IFC data of an IfcSite can be edited only in IFC Manager, you will not see the “Manage IFC Properties” interface in the Tags and Categories panel of such ArchiCAD elements.

•The types of the IFC Type Product generated automatically to an element can be checked and managed in IFC Manager only. Also, in some cases, the default IFC Type Product can be modified to an alternative IFC Type Product within the IFC Manager.

See IFC Type Product.

For details on these functions, see Find and Select Elements and Interactive Schedule.

Element conversion rules according to IFC element types at IFC model import:

•If the geometry of an imported IFC model element is “extruded” and can be recreated using an ArchiCAD tool (not an object-type tool), then the imported element will be converted into a native, editable ArchiCAD element. For example, an IfcBeam will become an ArchiCAD Beam.

•If the geometry of an imported IFC model element is “BREP”, or if it cannot be recreated with a non-object-type ArchiCAD tool (that is, it has no ArchiCAD tool counterpart), then it will be converted into an Object or a Morph (depending on the Import Options setting). For example, a BREP IfcBeam will be converted to an ArchiCAD Object with subtype Beam; an IfcCovering element will be converted to an ArchiCAD Object with subtype Covering, if the Import Option for this conversion is set to “Object”.

Note:

•Whether the created element is an Object or a Morph depends on the Geometry Conversion import option of the IFC Translator being used.

See Import Options of IFC Translators.

•“Extruded geometry” is the standard IFC geometry representation, which retains the elements’ parameter values (such as thickness, height, location of reference line or edge, skin structure of composites) - however, certain specialized sections are not retained. “Boundary representation” (BREP) geometry method comes closest to reproducing the shape of the element, together with its specialized sections and connections (but the element’s parameters are lost).

•Naturally, whether a given element or element type is imported at all depends on the Model Element Filter settings or the import options of the IFC Translator.