#### IfcBuildingStorey

Natural language names

##### Semantic definitions at the entity

Entity definition

The building storey has an elevation and typically represents a (nearly) horizontal aggregation of spaces that are vertically bound.

A storey is (if specified) associated to a building. A storey may span over several connected storeys. Therefore storey complex provides for a collection of storeys included in a building. A storey can also be decomposed in (horizontal) parts, where each part defines a partial storey. This is defined by the composition type attribute of the supertype IfcSpatialStructureElements which is interpreted as follow:

- COMPLEX = building storey complex
- ELEMENT = building storey
- PARTIAL = partial building storey

> EXAMPLE: In split level houses, a storey is split into two or more partial storeys, each with a different elevation. It can be handled by defining a storey, which includes two or more partial storeys with the individual elevations.

> HISTORY New entity in IFC Release 1.0

Property Set Use Definition

The property sets relating to the IfcBuildingStorey are defined by the IfcPropertySet and attached by the IfcRelDefinesByProperties relationship. It is accessible by the inverse IsDefinedBy relationship. The following property set definitions specific to the IfcBuildingStorey are part of this IFC release:

- Pset_BuildingStoreyCommon: common property set for all types of building stories

Quantity Use Definition

The quantities relating to the building storey 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
NominalHeight | Standard height of this storey, from the bottom surface of the floor, to the bottom surface of the floor or roof above. The exact definition and calculation rules depend on the method of measurement used. | IfcQuantityLength
GrossFloorArea | Calculated sum of all areas covered by the building storey (as horizontal projections and normally including the area of construction elements. 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 storey (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 storey (normally including the area of construction elements). The exact definition and calculation rules depend on the method of measurement used. | IfcQuantityVolume
NetVolume | Calculated net volume of all areas enclosed by the building storey (normally excluding the area of construction elements). The exact definition and calculation rules depend on the method of measurement used. | IfcQuantityVolume

Spatial Structure Use Definition

The IfcBuildingStorey 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. The IfcBuildingStoreyreferences them by its inverse relationships:

- IfcBuildingStorey.Decomposes -- referencing (IfcBuilding || IfcBuildingStorey) by IfcRelAggregates.RelatingObject, If it refers to another instance of IfcBuildingStorey, the referenced IfcBuildingStorey needs to have a different and higher CompositionType, i.e. COMPLEX (if the other IfcBuildingStorey has ELEMENT), or ELEMENT (if the other IfcBuildingStorey has PARTIAL).
- IfcBuildingStorey.IsDecomposedBy -- referencing (IfcBuildingStorey || IfcSpace) by IfcRelAggregates.RelatedObjects. If it refers to another instance of IfcBuildingStorey, the referenced IfcBuildingStorey needs to have a different and lower CompositionType, i.e. ELEMENT (if the other IfcBuildingStorey has COMPLEX), or PARTIAL (if the other IfcBuildingStorey has ELEMENT).

If there are building elements and/or other elements directly related to the IfcBuildingStorey (like most building elements, such as walls, columns, etc.), they are associated with the IfcBuildingStorey by using the objectified relationship IfcRelContainedInSpatialStructure. The IfcBuildingStorey references them by its inverse relationship:

- IfcBuildingStorey.ContainsElements -- referencing any subtype of IfcProduct (with the exception of other spatial structure element) by IfcRelContainedInSpatialStructure.RelatedElements.

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

Geometry Use Definitions

The geometric representation of IfcBuildingStorey is given by the IfcProductDefinitionShape and IfcLocalPlacement, allowing multiple geometric representation.

Local Placement

The local placement for IfcBuildingStorey 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 IfcBuilding, or of type IfcBuildingStorey (e.g. to position a building storey relative to a building storey complex, or a partial building storey to a building storey).
- 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 'GeometricCurveSet' and a 3D 'Body' representation of type 'Brep' is supported.

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

Foot Print Representation

The foot print representation of IfcBuildingStorey 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 storey has an independent geometric representation.

The representation identifier and type of this geometric representation of IfcBuildingStorey is:

- IfcShapeRepresentation.RepresentationIdentifier = 'FootPrint'
- IfcShapeRepresentation.RepresentationType = 'GeometricCurveSet'

Body Representation

The body (or solid model) geometric representation (if the building storey has an independent geometric representation) of IfcBuildingStorey 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 IfcBuildingStorey is:

- IfcShapeRepresentation.RepresentationIdentifier = 'Body'
- IfcShapeRepresentation.RepresentationType = 'Brep'

Since the building storey shape is usually described by the exterior building elements, an independent shape representation shall only be given, if the building storey is exposed independently from its constituting elements.

Attribute definitions

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
10 | Elevation | - |  | This attribute is out of scope for this model view definition and shall not be set. |

##### Inherited definitions from supertypes

Entity inheritance
Attribute inheritance

# | Attribute | Type | Cardinality | Description | A
--- | --- | --- | --- | --- | ---
IfcRoot
1 | GlobalId | IfcGloballyUniqueId | [1:1] | Assignment of a globally unique identifier within the entire software world. | X
2 | OwnerHistory | IfcOwnerHistory | [1:1] | Assignment of the information about the current ownership of that object, including owning actor, application, local identification and information captured about the recent changes of the object, NOTE: only the last modification in stored. | X
3 | Name | IfcLabel | [0:1] | Optional name for use by the participating software systems or users. For some subtypes of IfcRoot the insertion of the Name attribute may be required. This would be enforced by a where rule. | X
4 | Description | IfcText | [0:1] | Optional description, provided for exchanging informative comments. | X
IfcObjectDefinition
| IsDecomposedBy | IfcRelDecomposes @RelatingObject | S[0:?] | Reference to the decomposition relationship, that allows this object to be the composition of other objects. An object can be decomposed by several other objects. | X
| Decomposes | IfcRelDecomposes @RelatedObjects | S[0:1] | References to the decomposition relationship, that allows this object to be a part of the decomposition. An object can only be part of a single decomposition (to allow hierarchical strutures only). | X
| HasAssociations | IfcRelAssociates @RelatedObjects | S[0:?] | Reference to the relationship objects, that associates external references or other resource definitions to the object.. Examples are the association to library, documentation or classification. | X
IfcObject
5 | ObjectType | IfcLabel | [0:1] | The type denotes a particular type that indicates the object further. The use has to be established at the level of instantiable subtypes. In particular it holds the user defined type, if the enumeration of the attribute PredefinedType is set to USERDEFINED. | X
| IsDefinedBy | IfcRelDefines @RelatedObjects | S[0:?] | Set of relationships to type or property (statically or dynamically defined) information that further define the object. In case of type information, the associated IfcTypeObject contains the specific information (or type, or style), that is common to all instances of IfcObject referring to the same type. | X
IfcProduct
6 | ObjectPlacement | IfcObjectPlacement | [0:1] | Placement of the product in space, the placement can either be absolute (relative to the world coordinate system), relative (relative to the object placement of another product), or constraint (e.g. relative to grid axes). It is determined by the various subtypes of IfcObjectPlacement, which includes the axis placement information to determine the transformation for the object coordinate system. | X
7 | Representation | IfcProductRepresentation | [0:1] | Reference to the representations of the product, being either a representation (IfcProductRepresentation) or as a special case a shape representations (IfcProductDefinitionShape). The product definition shape provides for multiple geometric representations of the shape property of the object within the same object coordinate system, defined by the object placement. | X
IfcSpatialStructureElement
8 | LongName | - |  | This attribute is out of scope for this model view definition and shall not be set. |
9 | CompositionType | IfcElementCompositionEnum | [1:1] | Denotes, whether the predefined spatial structure element represents itself, or an aggregate (complex) or a part (part). The interpretation is given separately for each subtype of spatial structure element. | X
| ContainsElements | IfcRelContainedInSpatialStructure @RelatingStructure | S[0:?] | Set of spatial containment relationships, that holds those elements, which are contained within this element of the project spatial structure. NOTE The spatial containment relationship, established by IfcRelContainedInSpatialStructure, is required to be an hierarchical relationship, i.e. each element can only be assigned to 0 or 1 spatial structure element. | X
IfcBuildingStorey
10 | Elevation | - |  | This attribute is out of scope for this model view definition and shall not be set. |

##### Definitions applying to AISC Model View

Instance diagram

Concept usage

Spatial Composition

The Spatial Composition concept applies to this entity as shown in Table 1.

RelatingObject
IfcBuilding
IfcStair
Table 1 — IfcBuildingStorey Spatial Composition

Exchange |
--- | ---
Import | R
Export | R

Placement

The Placement concept applies to this entity.

Exchange |
--- | ---
Import | R
Export | R

Spatial Container

The Spatial Container concept applies to this entity.

Exchange |
--- | ---
Import | R
Export | R

Concept inheritance

# | Concept | Model View
--- | --- | ---
IfcBuildingStorey
| Spatial Composition | AISC Model View
| Placement | AISC Model View
| Spatial Container | AISC Model View

##### Formal representations

XSD Specification
`<xs:element name="IfcBuildingStorey" type="ifc:IfcBuildingStorey" substitutionGroup="ifc:IfcSpatialStructureElement" nillable="true"/>
<xs:complexType name="IfcBuildingStorey">
<xs:complexContent>
<xs:extension base="ifc:IfcSpatialStructureElement"/>
</xs:complexContent>
</xs:complexType>
`
EXPRESS Specification
`ENTITY IfcBuildingStorey
SUBTYPE OF (IfcSpatialStructureElement);
Elevation : OPTIONAL IfcStrippedOptional;
END_ENTITY;

EXPRESS-G diagram

`

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