IFC - Industry Foundation Classes/IFC materials

IFC can store information about real life materials, and objects can be assigned to materials. Materials may contain attributes like a name and description, and contain physical properties. Some of these properties are part of the IFC standard, such as concrete strength, thermal properties, or mechanical properties, or it may be a custom property defined by the user.

A material may be assigned directly to an object. However, for more complex materials, it is possible to create a composite material from multiple materials. This composite material is known as a material "set" in IFC, and may then be assigned to an object. There are three distinct types of composite material sets.

• Material layer set
• Material constituent set
• Material profile set

When a material set is defined, it is sometimes necessary to describe which parts of the geometry a portions of the material set applies to. For example, when an object has a material layer set, we need to describe the start and end point of each sub material. When we describe a material set assignment parametrically, this is known as a material set usage. There are two types of parametric usages that can be defined in IFC:

• Material layer set usage
• Material profile set usage

A material may also have a visual style associated with it, such as a colour. When viewing an IFC model, the colour of an object may represent its material.

However, it is also possible for IFC objects to be assigned a visual style or colour that is not associated with a material. This is a common cause for confusion, as users may think a colour represents a material. It is made more confusing by the fact that a visual style may have a name. This name is not the same as a material name, but some BIM software may not make the distinction between them.

A visual style may be used to represent non-material information. One common usecase is when a style correlates with a discipline. For example, all hydraulic objects may be coloured blue, and all mechanical objects may be coloured green. The concept of visual styles is a separate concept to materials, and will not be described further here.

Single Material

The simplest possible material definition is a single material by itself. For example, a stirrup or a pipe might have their material assigned this way.

Attribute	Required	Description
Name	Recommended	This can store the name of the material. If a material is given a unique label or tag that is referenced in documentation annotation or schedules, this is where it should be stored. It is usually a short, coded name.
Description	Recommended	This allows you to write a sentence or so to describe the material in human terms.
Category	Recommended	Sometimes, it is important to broadly categorise materials to isolate them for costing or procurement purposes. There is no strict requirement on what categories are allowed, but it is highly recommended to use the value "Concrete", "Steel" or blank.

It is possible for a single material to have IFC properties assigned to it. The following sets are defined by the buildingSMART standard, and should be available in your BIM authoring application. If you wish to store a property that is not part of the standard, you may be define your own property set.

Property Set	Description
Pset_MaterialCombustion	Used to store chemical properties of combustible materials.
Pset_MaterialCommon	Generic material properties.
Pset_MaterialEnergy	TODO
Pset_MaterialFuel	TODO
Pset_MaterialHygroscopic	TODO
Pset_MaterialMechanical	Useful to describing mechanical properties, usually relevant to structural analysis.
Pset_MaterialOptical	TODO
Pset_MaterialThermal	TODO
Pset_MaterialWater	TODO

Material Constituent Set

There are two typical usages of a material constituent set.

A typical usage for material constituent set is a door or a window made of different part like frame + glass :

Material Layer Set

Typical usage for material layer set is a wall which is often made of multiple layers as concrete + insulation + plaster :

Material Profile Set

Typical usage for material profile set is a duct, pipe or a beam :

Assignment example

Following diagram shows how materials are related to their object. Any child of IfcObjectDefinition as IfcWall, IfcDuct etc… can get a material assigned this way :