|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
There are three entities for slab occurrences:
- IfcSlabStandardCase used for all occurrences of slabs,
that are prismatic and where the thickness parameter can be fully
described by the IfcMaterialLayerSetUsage. These slabs are
always represented geometrically by a 'SweptSolid' geometry (or
by a 'Clipping' geometry based on 'SweptSolid'), if a 3D
geometric representation is assigned. In addition they have to
have a corresponding IfcMaterialLayerSetUsage
- IfcSlabElementedCase used for occurrences of slabs
which are aggregated from subordinate elements, following
specific decomposition rules expressed by the mandatory use of
- IfcSlab used for all other occurrences of slabs,
particularly for slabs with changing thickness, or slabs with non
planar surfaces, and slabs having only 'SweptSolid' or 'Brep'
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:
- IfcRoot: Identity, Revision Control
- IfcElement: Product Placement, Box Geometry, FootPrint Geometry, Body SurfaceOrSolidModel Geometry, Body SurfaceModel Geometry, Body Tessellation Geometry, Body Brep Geometry, Body AdvancedBrep Geometry, Body CSG Geometry, Mapped Geometry
- IfcBuildingElement: Surface 3D Geometry
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
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.
The Spatial Containment concept applies to this entity as shown in Table 167.
|IfcBuildingStorey||Default spatial container|
|IfcBuilding||Spatial container for the element if it cannot be assigned to a building storey|
|IfcSite||Spatial 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:
- the Spatial Containment (defined here), or
- the Element Composition.
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
- Solid: IfcExtrudedAreaSolid is required,
- Profile: IfcArbitraryClosedProfileDef,
IfcEllipseProfileDef shall be supported.
- Extrusion: The profile can be extruded perpendicularly
or non-perpendicularly to the plane of the swept profile.
Figure 208 illustrates a 'SweptSolid' geometric representation.
NOTE The following interpretation of dimension parameter applies for polygonal slabs (in ground floor view):
- IfcArbitraryClosedProfileDef.OuterCurve: closed bounded curve interpreted as area (or foot print) of the 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'
- Solid: see 'SweptSolid' shape representation,
- Profile: see 'SweptSolid' shape representation,
- Extrusion: see 'SweptSolid' shape representation,
- Boolean result: The IfcBooleanClippingResult
shall be supported, allowing for Boolean differences between the
swept solid (here IfcExtrudedAreaSolid) and one or several
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.
Figure 209 — Slab body clipping
The Element Voiding concept applies to this entity as shown in Table 168.
The Product Assignment concept applies to this entity as shown in Table 169.
Table 169 — IfcSlab Product Assignment
XSD Specification: <xs:element name="IfcSlab" type="ifc:IfcSlab" substitutionGroup="ifc:IfcBuildingElement" nillable="true"/>
<xs:attribute name="PredefinedType" type="ifc:IfcSlabTypeEnum" use="optional"/>
|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.RelatingType));|
|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.
|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.
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