Decke / Dachfläche / Bodenplatte

A slab is a component of the construction that normally encloses a space vertically. The slab may provide the lower support (floor) or upper construction (roof slab) in any space in a building.

NOTE  Definition according to ISO 6707-1
thick, flat or shaped component, usually larger than 300 mm square, used to form a covering or projecting from a building.

Only the core or constructional part of this construction is considered to be a slab. The upper finish (flooring, roofing) and the lower finish (ceiling, suspended ceiling) are considered to be coverings. A special type of slab is the landing, described as a floor section to which one or more stair flights or ramp flights connect.

NOTE  There is a representation of slabs for structural analysis provided by a proper subtype of IfcStructuralMember being part of the IfcStructuralAnalysisModel.
NOTE  An arbitrary planar element to which this semantic information is not applicable or irrelevant shall be modeled as IfcPlate.

A slab may have openings, such as floor openings, or recesses. They are defined by an IfcOpeningElement attached to the slab using the inverse relationship HasOpenings pointing to IfcRelVoidsElement.

There are three entities for slab occurrences:

HISTORY  New entity in IFC2.0; it is a merger of the two previous entities IfcFloor, IfcRoofSlab, introduced in IFC1.0

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 164.

Table 164 — IfcSlab Object Typing

Property Sets for Objects

The Property Sets for Objects concept applies to this entity as shown in Table 165.

Table 165 — IfcSlab Property Sets for Objects

Quantity Sets

The Quantity Sets concept applies to this entity as shown in Table 166.

Table 166 — IfcSlab Quantity Sets

Material Layer Set

The Material Layer Set concept applies to this entity.

The material of the IfcSlab is defined by IfcMaterialLayerSet, or as fallback by IfcMaterial, and it is attached either directly or at the IfcSlabType.

NOTE  It is illegal to assign an IfcMaterialLayerSetUsage to an IfcSlab. Only the subtype IfcSlabStandardCase supports this concept.

Spatial Containment

The Spatial Containment concept applies to this entity as shown in Table 167.
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 167 — IfcSlab Spatial Containment

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

Surface Geometry

The Surface Geometry concept applies to this entity.

NOTE  The 'Surface' can be used to define a surfacic model of the building (e.g. for analytical purposes, or for reduced Level of Detail representation).

Body SweptSolid Geometry

The Body SweptSolid Geometry concept applies to this entity.

The following additional constraints apply to the swept solid representation:

Figure 208 illustrates a 'SweptSolid' geometric representation.

NOTE  The following interpretation of dimension parameter applies for polygonal slabs (in ground floor view):
standard slab

Figure 208 — Slab body extrusion

Body Clipping Geometry

The Body Clipping Geometry concept applies to this entity.

The following constraints apply to the 'Clipping' representation:

Figure 209 illustrates a 'Clipping' geometric representation with definition of a roof slab using advanced geometric representation. The profile is extruded non-perpendicular and the slab body is clipped at the eave.

advanced slab

Figure 209 — Slab body clipping

Element Voiding

The Element Voiding concept applies to this entity as shown in Table 168.

Product Assignment

The Product Assignment concept applies to this entity as shown in Table 169.
IfcStructuralSurfaceMemberAn idealized structural member corresponding to the slab.
IfcTaskA task for operating on the slab.

Table 169 — IfcSlab Product Assignment

XSD Specification:

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

EXPRESS Specification:

SUPERTYPE OF(ONEOF(IfcSlabElementedCase, IfcSlabStandardCase))
SUBTYPE OF IfcBuildingElement;
PredefinedType : OPTIONAL IfcSlabTypeEnum;
CorrectPredefinedType : NOT(EXISTS(PredefinedType)) OR (PredefinedType <> IfcSlabTypeEnum.USERDEFINED) OR ((PredefinedType = IfcSlabTypeEnum.USERDEFINED) AND EXISTS (SELF\IfcObject.ObjectType));
CorrectTypeAssigned : (SIZEOF(IsTypedBy) = 0) OR ('IFCSHAREDBLDGELEMENTS.IFCSLABTYPE' IN TYPEOF(SELF\IfcObject.IsTypedBy[1].RelatingType));

Link to EXPRESS-G diagram EXPRESS-G diagram

Attribute Definitions:

PredefinedType : Predefined generic type for a slab 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 IfcSlabType is assigned, providing its own IfcSlabType.PredefinedType.
IFC2x CHANGE The attribute has been changed into an OPTIONAL attribute.

Formal Propositions:

CorrectPredefinedType : Either the PredefinedType attribute is unset (e.g. because an IfcSlabType is associated), or the inherited attribute ObjectType shall be provided, if the PredefinedType is set to USERDEFINED.
CorrectTypeAssigned : Either there is no slab type object associated, i.e. the IsTypedBy inverse relationship is not provided, or the associated type object has to be of type IfcSlabType.

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 IfcSlabTypeEnum;

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