Definition from IAI: A building (IfcBuilding) represents a structure that provides shelter for its occupants or contents and stands in one place. The building is also used to provide a basic element within the spatial structure hierarchy for the components of a building project (together with site, storey, and space).
A building is (if specified) associated to a site. A building may span over several connected or disconnected buildings. Therefore building complex provides for a collection of buildings included in a site. A building can also be decomposed in (vertical) parts, where each part defines a building section. This is defined by the composition type attribute of the supertype IfcSpatialStructureElements which is interpreted as follow:
- COMPLEX = building complex
- ELEMENT = building
- PARTIAL = building section
The quantities relating to the building are defined by the IfcElementQuantity and attached by the IfcRelDefinesByProperties. The following quantities are foreseen, but will be subjected to the local standard of measurement:
| Name | Description | Value Type |
| TotalHeight | Calculated total height of the building, measured from the level of terrain to the top part of the building | IfcQuantityLength |
| SiteCoverage | Calculated coverage of the building site area that is occupied by the building (also referred to as footprint). | IfcQuantityArea |
| GrossFloorArea | Calculated sum of all areas covered by the building. The exact definition and calculation rules depend on the method of measurement used. | IfcQuantityArea |
| NetFloorArea | Calculated sum of all usable areas covered by the building (normally excluding the area of construction elements). The exact definition and calculation rules depend on the method of measurement used. | IfcQuantityArea |
| GrossVolume | Calculated gross volume of all areas enclosed by the building. The exact definition and calculation rules depend on the method of measurement used. | IfcQuantityVolume |
HISTORY: New entity in IFC Release 1.0.
Use case:
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The heated space within a Building shall be handled by the IfcZone, including the property for overall height of the heated space in the Building. The following figure shall define the interpretation of building heights and elevations for IfcBuilding. The ElevationOfRefHeight is used to give the height above sea level of the internal height 0.00. The height 0.00 is often used as a building internal reference height and equal to the floor finish level of the ground floor. |
Geometry Use Definitions:
The geometric representation of IfcBuilding is given by the IfcProductDefinitionShape and IfcLocalPlacement, allowing multiple geometric representation.
Local Placement
The local placement for IfcBuilding is defined in its supertype IfcProduct. It is defined by the IfcLocalPlacement, which defines the local coordinate system that is referenced by all geometric representations.
- The PlacementRelTo relationship of IfcLocalPlacement shall point (if relative placement is used) to the IfcSpatialStructureElement of type "IfcSite", or of type "IfcBuilding" (e.g. to position a building relative to a building complex, or a building section to a building).
- If the relative placement is not used, the absolute placement is defined within the world coordinate system.
Geometric Representations
Currently, the use of a 2D 'FootPrint' representation of type 'Curve2D' or 'GeometricCurveSet' and a 3D 'Body' representation of type 'Brep' is supported.
Foot Print Representation
The foot print representation of IfcBuilding is given by either a single 2D curve (such as IfcPolyline or IfcCompositeCurve), or by a list of 2D curves (in case of inner boundaries), if the building has an independent geometric representation.
The representation identifier and type of this geometric representation of IfcBuilding is:
- IfcShapeRepresentation.RepresentationIdentifier = 'FootPrint'
- IfcShapeRepresentation.RepresentationType = 'Curve2D' or 'GeometricCurveSet'
Body Representation
The body (or solid model) geometric representation (if the building has an independent geometric representation) of IfcBuilding is defined using faceted B-Rep capabilities (with or without voids), based on the IfcFacetedBrep or on the IfcFacetedBrepWithVoids.
The representation identifier and type of this representation of IfcBuilding is:
- IfcShapeRepresentation.RepresentationIdentifier = 'Body'
- IfcShapeRepresentation.RepresentationType = 'Brep'
Since the building shape is usually described by the exterior building elements, an independent shape representation shall only be given, if the building is exposed independently from its constituting elements.