# 8.10.3.9 IfcMaterialLayerWithOffsets

## 8.10.3.9.1 Semantic definition

IfcMaterialLayerWithOffsets is a specialization of IfcMaterialLayer enabling definition of offset values along edges (within the material layer set usage in parent layer set).

It defines the assignment of two offset values for a material layer in its intended use within a material layer set. Offsets are applied to the edges of layered elements (that is, in directions perpendicular to the layer set direction). Offsets shall not be used in layer set direction, that is, for modelling gaps (or overlaps) between layers; gaps shall be modeled as layers with appropriate material assignment for the void.

Take a layered wall with the outer material layer for the external isolation extending above extrusion by 100mm, but starting at the same base height. In this case the following values are set: > * OffsetDirection = .AXIS3. * OffsetValues[1] = 0.0 * OffsetValues[2] = 100.0 (default unit assumed to be mm)

Informal Propositions:

1. The OffsetDirection shall not be identical to the LayerSetDirection of the corresponding IfcMaterialLayerSetUsage.

2. The attribute ReferenceExtent shall be asserted at the corresponding IfcMaterialLayerSetUsage.

The OffsetValues and OffsetDirection correspond to the definitions ReferenceExtent and LayerSetDirection at the IfcMaterialLayerSetUsage. Figure 8.10.3.9.A shows an example of applying the OffsetValues to the material layers of a layered wall.

## 8.10.3.9.4 Formal representation

ENTITY IfcMaterialLayerWithOffsets
SUBTYPE OF (IfcMaterialLayer);
OffsetDirection : IfcLayerSetDirectionEnum;
OffsetValues : ARRAY [1:2] OF IfcLengthMeasure;
END_ENTITY;