A stair is a vertical passageway allowing occupants to walk (step) from one floor level to another floor level at a different elevation. It may include a landing as an intermediate floor slab.

NOTE  Definition according to ISO 6707-1: Construction comprising a succession of horizontal stages (steps or landings) that make it possible to pass on foot to other levels.

The IfcStair shall either be represented:

NOTE  In case of an IfcStair being the aggregate of all components of the stair the aggregation is handled by the IfcRelAggregates relationship, relating an IfcStair with the related IfcStairFlight and landings, IfcSlab with PredefinedType=LANDING. IfcRailing's belonging to the stair may also be included into the aggregation.
NOTE  The 'Body' geometric representation shall only be provided if the IfcStair has no components defined (empty set of SELF\IfcObject.IsDecomposedBy).
HISTORY  New entity in IFC2.0.
IFC4 CHANGE Attribute ShapeType renamed to PredefinedType.

Common Use Definitions

The following concepts are inherited at supertypes:

 Instance diagram

Object Typing

The Object Typing concept applies to this entity as shown in Table 173.

Table 173 — IfcStair Object Typing

Property Sets for Objects

The Property Sets for Objects concept applies to this entity as shown in Table 174.

Table 174 — IfcStair Property Sets for Objects

Material Single

The Material Single concept applies to this entity.

The material of the IfcStair is defined by the IfcMaterial and attached by the IfcRelAssociatesMaterial.RelatingMaterial. It is accessible by the inverse HasAssociations relationship.

Material information can also be given at the IfcStairType, defining the common attribute data for all occurrences of the same type. It is then accessible by the inverse IsDefinedBy relationship pointing to IfcStair.HasAssociations and via IfcRelAssociatesMaterial.RelatingMaterial to IfcMaterial. If both are given, then the material directly assigned to IfcStair overrides the material assigned to IfcStairType.

Spatial Containment

The Spatial Containment concept applies to this entity as shown in Table 175.
IfcBuildingStoreyDefault spatial container
IfcBuildingSpatial container for the element if it cannot be assigned to a building storey
IfcSiteSpatial container for the element in case that it is placed on site (outside of building)

Table 175 — IfcStair Spatial Containment

The IfcStair, as any subtype of IfcBuildingElement, may participate alternatively in one of the two different containment relationships:

Element Decomposition

The Element Decomposition concept applies to this entity as shown in Table 176.
IfcStairFlightStairs may be decomposed into stair flights.
IfcSlabStairs may be decomposed into stair landing, represented by IfcSlab.PredefinedType=LANDING
IfcRailingStairs may be decomposed into railings for zero, one, or both sides.

Table 176 — IfcStair Element Decomposition

Geometric representation by aggregated elements

If the IfcStair has components (referenced by SELF\IfcObject.IsDecomposedBy) with own 'Body' representation, then no 'Body' representation shall defined for the IfcStair. The IfcStair shape is then represented by the geometric representation of its components. The components are accessed via SELF\IfcObject.IsDecomposedBy[1].RelatedObjects.

Figure 215 illustrates stair placement, where the IfcStair defines the local placement for all components and the common 'Axis' representation, and each component has its own 'Body' representation.


Figure 215 — Stair placement

Product Placement

The Product Placement concept applies to this entity as shown in Table 177.
IfcLocalPlacementIfcLocalPlacementRelative placement according to position and rotation relative to container.
IfcLocalPlacement Absolute placement according to position and rotation of world coordinate system.
IfcGridPlacement Placement according to grid intersection.

Table 177 — IfcStair Product Placement

The following restriction may be imposed by view definitions or implementer agreements:

Axis 2D Geometry

The Axis 2D Geometry concept applies to this entity.

The walking line is represented by a two-dimensional open curve as the axis. The curve is directed into the upward direction (direction has to be interpreted as specified at the subtypes of IfcCurve).

NOTE  The 'Axis' representation of IfcStair may be provided even if the IfcStair has components with own shape representations.

Body SweptSolid Geometry

The Body SweptSolid Geometry concept applies to this entity.

XSD Specification:

 <xs:element name="IfcStair" type="ifc:IfcStair" substitutionGroup="ifc:IfcBuildingElement" nillable="true"/>
 <xs:complexType name="IfcStair">
   <xs:extension base="ifc:IfcBuildingElement">
    <xs:attribute name="PredefinedType" type="ifc:IfcStairTypeEnum" use="optional"/>

EXPRESS Specification:

SUBTYPE OF IfcBuildingElement;
PredefinedType : OPTIONAL IfcStairTypeEnum;
CorrectShapeDecomposition : (HIINDEX(SELF\IfcObjectDefinition.IsDecomposedBy) = 0) OR ((HIINDEX(SELF\IfcObjectDefinition.IsDecomposedBy) = 1) AND ((NOT(EXISTS(SELF\IfcProduct.Representation))) OR ((EXISTS(SELF\IfcProduct.Representation)) AND (SIZEOF(QUERY( temp <* SELF\IfcProduct.Representation.Representations | temp.RepresentationIdentifier = 'Body')) = 0 ) ) ) );
CorrectPredefinedType : NOT(EXISTS(PredefinedType)) OR (PredefinedType <> IfcStairTypeEnum.USERDEFINED) OR ((PredefinedType = IfcStairTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType));
CorrectTypeAssigned : (SIZEOF(IsTypedBy) = 0) OR ('IFCSHAREDBLDGELEMENTS.IFCSTAIRTYPE' IN TYPEOF(SELF\IfcObject.IsTypedBy[1].RelatingType));

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

PredefinedType : Predefined generic type for a stair that is specified in an enumeration. There may be a property set given specifically for the predefined types.
NOTE  The PredefinedType shall only be used, if no IfcStairType is assigned, providing its own IfcStairType.PredefinedType.
IFC4 CHANGE The attribute has been renamed from ShapeType and changed to be OPTIONAL with upward compatibility for file based exchange.

Formal Propositions:

CorrectShapeDecomposition : Either the IfcStair is not decomposed into its flights and landings, then the IfcStair may have independent geometry. Or the IfcStair is decomposed into parts, then the IfcStair shall not have an own geometric shape representation of RepresentationType = 'Body'.
CorrectPredefinedType : Either the PredefinedType attribute is unset (e.g. because an IfcStairType is associated), or the inherited attribute ObjectType shall be provided, if the PredefinedType is set to USERDEFINED.
CorrectTypeAssigned : Either there is no stair type object associated, i.e. the IsTypedBy inverse relationship is not provided, or the associated type object has to be of type IfcStairType.

Inheritance Graph:

GlobalId : IfcGloballyUniqueId;
OwnerHistory : OPTIONAL IfcOwnerHistory;
Name : OPTIONAL IfcLabel;
Description : OPTIONAL IfcText;
ENTITY IfcObjectDefinition
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;
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;
ReferencedBy : SET OF IfcRelAssignsToProduct FOR RelatingProduct;
ENTITY IfcElement
Tag : OPTIONAL IfcIdentifier;
FillsVoids : SET [0:1] OF IfcRelFillsElement FOR RelatedBuildingElement;
ConnectedTo : SET OF IfcRelConnectsElements FOR RelatingElement;
IsInterferedByElements : SET OF IfcRelInterferesElements FOR RelatedElement;
InterferesElements : SET OF IfcRelInterferesElements FOR RelatingElement;
HasProjections : SET OF IfcRelProjectsElement FOR RelatingElement;
ReferencedInStructures : SET OF IfcRelReferencedInSpatialStructure FOR RelatedElements;
HasOpenings : SET OF IfcRelVoidsElement FOR RelatingBuildingElement;
IsConnectionRealization : SET OF IfcRelConnectsWithRealizingElements FOR RealizingElements;
ProvidesBoundaries : SET OF IfcRelSpaceBoundary FOR RelatedBuildingElement;
ConnectedFrom : SET OF IfcRelConnectsElements FOR RelatedElement;
ContainedInStructure : SET [0:1] OF IfcRelContainedInSpatialStructure FOR RelatedElements;
ENTITY IfcBuildingElement
HasCoverings : SET OF IfcRelCoversBldgElements FOR RelatingBuildingElement;
PredefinedType : OPTIONAL IfcStairTypeEnum;

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