**CV-2x3-100**

Correct usage of IfcMaterialLayerSetUsage for IfcSlab [modified 15-12-2006]

**Based on** IFC2x3

**Initiator** ISG Meeting-Berlin

**Effects** Extended Coordination View

**Date ** 2006 02 24

**Description:**

** **

For standard, prismatic slabs, the support of IfcMaterialLayerSetUsage is mandatory. This effects all usage of IfcSlab for floor slabs, roof slabs, base slabs, landings, etc.

The following conventions are agreed:

* Reference geometry: the extruded profile (plane) of *IfcExtrudedAreaSolid.SweptSolid* is the reference area. The *IfcMaterialLayerSetUsage.OffsetFromReferenceLine* is given as a distance from this plane.

* The reference coordinate system: coordinate system of the *IfcExtrudedAreaSolid.Position*.

** IfcMaterialLayerSetUsage.DirectionSense* = Positve : the site of the plane where the positive extrusion direction is. TRUE means into the positive z-axis of the position as defined by the *IfcExtrudedAreaSolid.Position*. A positve value of *IfcMaterialLayerSetUsage.OffsetFromReferenceLine* would then point into the positive z-axis of the position.

* *IfcMaterialLayerSetUsage.OffsetFromReferenceLine* is the distance parallel to the base plane and perpendicular to the base (XY) plane. This is independent of a potential non-perpendicular extrusion given by *IfcExtrudedAreaSolid.ExtrudedDirection* <> 0.,0.,1.

* The Thickness of each* IfcMaterialLayer* shall be the parallel distance (measured perpendicular to the base plane). The TotalThickness of the *IfcMaterialLayerSet* is the sum of all layer thicknesses and in case of a perpendicular extrusion identical with *IfcExtrudedAreaSolid.Depth*

* *IfcMaterialLayerSetUsage.LayerSetDirection* = AXIS3 (always)

**Figures:**

Figure 1: Applying a material layer set usage to *IfcSlab* being a horizontal slab.

Figure 2: Applying a material layer set usage to *IfcSlab* being a sloped roof slab.