5.4.3.2 IfcBuilding

Bâtiment
Gebäude

A building 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).

NOTE  Definition from ISO 6707-1:
Construction work that has the provision of shelter for its occupants or contents as one of its main purpose and is normally designed to stand permanently in one place.

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:

The IfcBuilding is used to build the spatial structure of a building (that serves as the primary project breakdown and is required to be hierarchical). The spatial structure elements are linked together by using the objectified relationship IfcRelAggregates.

HISTORY  New entity in IFC1.0.

Figure 111 shows the IfcBuilding as part of the spatial structure. It also serves as the spatial container for building and other elements.

NOTE  Detailed requirements on mandatory element containment and placement structure relationships are given in view definitions and implementer agreements.
IfcBuildingStorey as part of a spatial structure

Figure 111 — Building composition

Systems, such as building service or electrical distribution systems, zonal systems, or structural analysis systems, relate to IfcBuilding by using the objectified relationship IfcRelServicesBuildings.

Attribute Use Definition

Figure 112 describes the heights and elevations of the IfcBuilding. It is used to provide the height above sea level of the project height datum for this building, that is, 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.

building heights 

Figure 112 — Building elevations


Common Use Definitions

The following concepts are inherited at supertypes:

 Instance diagram

Spatial Composition

The Spatial Composition concept applies to this entity as shown in Table 23.
Spatial CompositeDescription
IfcProjectDirect assignment to project, if the building is the outermost spatial container, and no site information is provided for building projects
IfcSiteAssignment to site, if the building is the spatial container for the building project with site information
IfcBuildingAssignment to another building as spatial container, e.g. if this building represents a building section.

Table 23 — IfcBuilding Spatial Composition

NOTE  By using the inverse relationship IfcBuilding.Decomposes it references IfcProject || IfcSite || IfcBuilding through IfcRelAggregates.RelatingObject. If it refers to another instance of IfcBuilding, the referenced IfcBuilding needs to have a different and higher CompositionType, i.e. COMPLEX (if the other IfcBuilding has ELEMENT), or ELEMENT (if the other IfcBuilding has PARTIAL).


Spatial Decomposition

The Spatial Decomposition concept applies to this entity as shown in Table 24.
Spatial PartsDescription
IfcBuildingStoreySpatial decomposition into building stories.
IfcBuildingSpatial decomposition into other buildings, e.g. if this building represents a complex building that is subdivided into building sections.

Table 24 — IfcBuilding Spatial Decomposition

NOTE  By using the inverse relationship IfcBuilding.IsDecomposedBy it references IfcBuilding || IfcBuildingStorey through IfcRelAggregates.RelatedObjects. If it refers to another instance of IfcBuilding, the referenced IfcBuilding needs to have a different and lower CompositionType, i.e. ELEMENT (if the other IfcBuilding has COMPLEX), or PARTIAL (if the other IfcBuilding has ELEMENT).


Spatial Container

The Spatial Container concept applies to this entity as shown in Table 25.
Contained elementsDescription
IfcElementPhysical elements contained in the building.
IfcAnnotationAnnotations that are directly related to the building.
IfcGridGrids that are directly related to the building.

Table 25 — IfcBuilding Spatial Container

NOTE  If there are building elements and/or other elements directly related to the IfcBuilding (like a curtain wall spanning several stories), they are associated with the IfcBuilding by using the objectified relationship IfcRelContainedInSpatialStructure. The IfcBuilding references them by its inverse relationship:


Property Sets for Objects

The Property Sets for Objects concept applies to this entity as shown in Table 26.
PredefinedTypeName
 Pset_BuildingCommon
 Pset_BuildingUse
 Pset_BuildingUseAdjacent
 Pset_OutsideDesignCriteria
 Pset_UtilityConsumptionPHistory
 Pset_PropertyAgreement
 Pset_AirSideSystemInformation
 Pset_SpaceFireSafetyRequirements
 Pset_SpaceLightingRequirements
 Pset_SpaceOccupancyRequirements
 Pset_SpaceThermalRequirements
 Pset_ThermalLoadAggregate
 Pset_ThermalLoadDesignCriteria

Table 26 — IfcBuilding Property Sets for Objects



Quantity Sets

The Quantity Sets concept applies to this entity as shown in Table 27.
Name
Qto_BuildingBaseQuantities

Table 27 — IfcBuilding Quantity Sets



Product Placement

The Product Placement concept applies to this entity.

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.



FootPrint GeomSet Geometry

The FootPrint GeomSet Geometry concept applies to this entity as shown in Table 28.
IdentifierTypeItemsDescription
FootPrintGeometricCurveSetIfcGeometricCurveSetSet of curves (outer and inner) representing the floor projection,

Table 28 — IfcBuilding FootPrint GeomSet Geometry

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.

NOTE  The independent geometric representation of IfcBuilding may not be allowed in certain model view definitions. In those cases only the contained elements and spaces have an independent geometric representation.


Body Geometry

The Body Geometry concept applies to this entity.

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.

NOTE  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 and such independent geometric representation may be prohibited in model view definitions.



XSD Specification:

 <xs:element name="IfcBuilding" type="ifc:IfcBuilding" substitutionGroup="ifc:IfcSpatialStructureElement" nillable="true"/>
 <xs:complexType name="IfcBuilding">
  <xs:complexContent>
   <xs:extension base="ifc:IfcSpatialStructureElement">
    <xs:sequence>
     <xs:element name="BuildingAddress" type="ifc:IfcPostalAddress" nillable="true" minOccurs="0"/>
    </xs:sequence>
    <xs:attribute name="ElevationOfRefHeight" type="ifc:IfcLengthMeasure" use="optional"/>
    <xs:attribute name="ElevationOfTerrain" type="ifc:IfcLengthMeasure" use="optional"/>
   </xs:extension>
  </xs:complexContent>
 </xs:complexType>

EXPRESS Specification:

ENTITY IfcBuilding
SUBTYPE OF IfcSpatialStructureElement;
ElevationOfRefHeight : OPTIONAL IfcLengthMeasure;
ElevationOfTerrain : OPTIONAL IfcLengthMeasure;
BuildingAddress : OPTIONAL IfcPostalAddress;
END_ENTITY;

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

ElevationOfRefHeight : Elevation above sea level of the reference height used for all storey elevation measures, equals to height 0.0. It is usually the ground floor level.
ElevationOfTerrain : Elevation above the minimal terrain level around the foot print of the building, given in elevation above sea level.
BuildingAddress : Address given to the building for postal purposes.

Inheritance Graph:

ENTITY IfcBuilding
ENTITY IfcRoot
GlobalId : IfcGloballyUniqueId;
OwnerHistory : OPTIONAL IfcOwnerHistory;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ENTITY IfcObjectDefinition
INVERSE
HasAssignments : SET OF IfcRelAssigns FOR RelatedObjects;
Nests : SET [0:1] OF IfcRelNests FOR RelatedObjects;
IsNestedBy : SET OF IfcRelNests FOR RelatingObject;
HasContext : SET [0:1] OF IfcRelDeclares FOR RelatedDefinitions;
IsDecomposedBy : SET OF IfcRelAggregates FOR RelatingObject;
Decomposes : SET [0:1] OF IfcRelAggregates FOR RelatedObjects;
HasAssociations : SET OF IfcRelAssociates FOR RelatedObjects;
ENTITY IfcObject
ObjectType : OPTIONAL IfcLabel;
INVERSE
IsDeclaredBy : SET [0:1] OF IfcRelDefinesByObject FOR RelatedObjects;
Declares : SET OF IfcRelDefinesByObject FOR RelatingObject;
IsTypedBy : SET [0:1] OF IfcRelDefinesByType FOR RelatedObjects;
IsDefinedBy : SET OF IfcRelDefinesByProperties FOR RelatedObjects;
ENTITY IfcProduct
ObjectPlacement : OPTIONAL IfcObjectPlacement;
Representation : OPTIONAL IfcProductRepresentation;
INVERSE
ReferencedBy : SET OF IfcRelAssignsToProduct FOR RelatingProduct;
ENTITY IfcSpatialElement
LongName : OPTIONAL IfcLabel;
INVERSE
ContainsElements : SET OF IfcRelContainedInSpatialStructure FOR RelatingStructure;
ServicedBySystems : SET OF IfcRelServicesBuildings FOR RelatedBuildings;
ReferencesElements : SET OF IfcRelReferencedInSpatialStructure FOR RelatingStructure;
ENTITY IfcSpatialStructureElement
CompositionType : OPTIONAL IfcElementCompositionEnum;
ENTITY IfcBuilding
ElevationOfRefHeight : OPTIONAL IfcLengthMeasure;
ElevationOfTerrain : OPTIONAL IfcLengthMeasure;
BuildingAddress : OPTIONAL IfcPostalAddress;
END_ENTITY;

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