IfcStairFlight
Definition from buildingSMART: Assembly of building components in a single "run" of stair steps (not interrupted by a landing). The stair steps and any stringers are included in this object. A winder is regarded as part of a stair flight.
An IfcStairFlight is normally aggregated by a stair (IfcStair) through the IfcRelAggregates relationship, the stair flight is then included in the set of IfcRelAggregates.RelatedObjects.
An IfcStairFlight normally connects the floor slab of zero to two different storeys (or partial storeys) within a building. The connection relationship between the IfcStairFlight and the IfcSlab is expressed using the IfcRelConnectsElements relationship.
HISTORY: New Entity in IFC Release 2.0.
Property Set Use Definition:
The property sets relating to the IfcStairFlight 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 IfcStairFlight are part of this IFC release:
Geometry Use Definitions:
The geometric representation of IfcStairFlight is given by the IfcProductDefinitionShape, allowing multiple geometric representation. Included are:
Local placement
The local placement for IfcStairFlight 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.
Standard Geometric Representation
The standard geometric representation of IfcStair is defined using the following multiple shape representations for its definition:
First Representation: WalkingLine
The walking line is represented by a twodimensional open curve within a particular shape representation. The curve is directed (direction has to be interpreted as specified at the subtypes of IfcCurve).
Second Representation: Boundary
The flight boundary is represented by a twodimensional closed curve within a particular shape representation.
Third Representation: Body
The three dimensional shape of the flight is represented by a Brep representation.
IfcShapeRepresentation RepresentationIdentifier : 'Body' RepresentationType : 'Brep' 
EXPRESS specification:

NumberOfRiser  :  Number of the risers included in the stair flight. 
NumberOfTreads  :  Number of treads included in the stair flight. 
RiserHeight  :  Vertical distance from tread to tread. The riser height is supposed to be equal for all stairs in a stair flight. 
TreadLength  :  Horizontal distance from the front to the back of the tread. The tread length is supposed to be equal
for all steps of the stair flight. 
