A stair flight is an 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 the stair flight. A winder is also regarded a part of a stair flight. 

An IfcStairFlight is normally aggregated by an 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, or landings) within a building. The connection relationship between the IfcStairFlight and the IfcSlab can be expressed using the IfcRelConnectsElements relationship. 

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). The image below illustrates the axis representation which has the following constraints:

• In case of straight flights the curve is a single item of type IfcPolyline
• In case of winding flights the curve is a single item of type IfcCompositeCurve
• In case of a curved flight or a spiral flight the curve is a single item of type IfcTrimmedCurve

The image below illustrates the 'Body' geometric representation using a 'SweptSolid' representation type. 

The flight foot print, including the flight boundary is represented by a two-dimensional geometric curve set. The image below illustrates the footprint representation which has the following constraints:

• In case of straight flights the curve set consists of a single item of type IfcPolyline
• In case of winding flights or curved flights the curve set consists of a single item of type IfcCompositeCurve
• In case of a spiral flight the curve set consists of a single item of type IfcConic or IfcPolyline