Material facet

Elements like walls, doors, windows, etc. in IFC may have a Material associated with them. In the simplest case, an element may have a single Material. For example, a chair may be made from a "wood" material. The Material Facet lets you filter, require or prohibit elements having this Material.

Many disciplines, such as costing, scheduling, sustainability and structural analysis depend on correct Material association and exact spelling.

Parameters

Parameter	Required	Restrictions Allowed	Meaning
Value	❌	✔️	Any material name or category. The material name is typically specific to the project or local convention. The element must be made out of a Material with the specified name or category. If there are multiple Materials, then any Material, Layer, Profile or Constituent with that name or category will also satisfy the requirement.
URI	❌	❌	Uniform Resource Identifier of the material. Used to reference a standardized definition of a material, to ensure consistency of interpretation. The target resource should include a name and definition, and preferably comply with the ISO 12006-3 and ISO 23386. This is an optional attribute that is not subject to IDS checking - the IFC model does not need to have the same or any URI. One source of valid URIs is the bSDD, and an example URI is that of a "Plywood": https://identifier.buildingsmart.org/uri/cei-bois.org/wood/1.0.0/class/8dca70a2-01a2-489b-9381-fbeff09db8dc.

* The material Category is an optional attribute of IfcMaterial, and is recommended by the IFC to be one of 'concrete', 'steel', 'aluminium', 'block', 'brick', 'stone', 'wood', 'glass', 'gypsum', 'plastic', or 'earth'.

The value field is optional. Optional attribute uri is only a metadata, not subject to IDS checking.

If no parameters are specified, then it means that any Material should be present, regardless of name or category.

IFC Material Relations

An element may have multiple Materials associated in three possible scenarios:

Layered materials: an element (e.g. a wall or slab) is parametrically defined in terms of material layers with a thickness (e.g. stud layer, insulation layer, and gypsum layer). Each layer may have a different Material.
Profiled materials: an element (e.g. a column or beam) is parametrically defined in terms of a profile (e.g. C-profile, Z-profile, or I-profile) extruded along a path. Composite columns and beams may have multiple profiles from different Materials.
Constituent materials: an element (e.g. a window, or slab) where portions of the element are made out of different Materials (e.g. the window glazing and the window frame) or mixed (e.g. a concrete slab may be composed of a percentage of cement, aggregate, etc)

Material Facet

In IFC (4x3 and before) materials (IfcMaterial) can be associated to objects (IfcObject) through IfcRelAssociatesMaterial relation.

However, the relation is not always direct. Sometimes objects are defined by a type or are parts aggregated in a larger assembly. Also, there are multiple ways to associate material with an object, for example, through a set of layers or as a list of constituents.

Material-relation

The IDS simplifies the material relation for its users, allowing them to simply specify material association, shifting the interpretation of various possible relations to IFC-IDS checking tools.

Material facet interpretation

Applicability

Material Value	IDS Interpretation
-	Applies to all entities with any associated material. Good way to filter only physical objects, given they have a material relation.
Steel	Applies to all entities with an associated material named Steel (exact spelling and case). It is not relevant if the entity has more material associations.

Requirements

IDS Cardinality	Material Value	Configuration Allowed?	IDS Interpretation
REQUIRED	-	✅	Applicable objects must have at least one related material, no matter its name.
REQUIRED	Steel	✅	Applicable objects must have the material Steel related. More materials are allowed.
OPTIONAL	-	❌	Not allowed. No added value in specifying that it can have material or not.
OPTIONAL	Steel	✅	Applicable objects don't need to have any materials, but if they do, Steel must be among them.
PROHIBITED	-	✅	Applicable objects must not have any materials associated.
PROHIBITED	Steel	✅	Steel must not be among the materials associated with applicable objects.

Examples of interpering IFC materials

IDS Material Value	IFC Material.Name	IFC Material.Category	IFCxIDS Result
Steel	Steel	-	✅
Steel	S275	-	❌
Steel	S275	Steel	✅
Brick	[Gypsum, Brick, Insulation]	-	✅