IFC-UniCLASS Entity Classification system

UniClass 2015 classification for IFC objects

UniClass is a unified classification system used in the BIM approach to organize everything required for built environment assets. Find out how to add a classification to IFC model entities according to the UniClass 2015 system 

If you need to address the tedious task of having to classify the entities of an IFC project, or do you have to read the classifications associated with the entities present in an IFC file, well today I’ll explain what the UniClass (Unified Classification for the Construction Industry) system is and what it is used for, including some useful info on how to use it to classify and add information to IFC Model entities.

I’ve also prepared an example in the IFC format on which you can try to classify objects yourself with usBIM.viewer + (the free software for managing IFC files).

What is the UniClass system?

UniClass is a classification system that was introduced for the first time in 1997 in the United Kingdom by the Construction Project Committee. It was born as an integration of existing standards such as EPIC (Electronic Product Information Cooperation) and CAWS (Common Arrangement of Work Sections for Building Works).

In the construction sector, UniClass can be defined as a “faceted” classification system, partly with an enumerative approach, which operates a classification method based on 15 tables and according to a hierarchy of tables.

Going into detail, the tables available in the UniClass classification are as follows:

  • Complexes: describes a project in overall terms. It can refer, for example, to residential buildings, sports buildings, school buildings, airports, etc.
  • Entity: constitutes one of the parts (or areas) of which a work is composed. It can include buildings, bridges or tunnels within a more complex system.
  • Activities: represents the activities to be carried out in a complex or in an entity. For example, in a school building, motor, administrative, recreational, training, etc. activities meet. The table also includes investigations, operation, maintenance and services.
  • Spaces: they can host one or more activities, inside a building or related to non-punctual works, such as road systems, railway networks, etc.
  • Elements: they are the main components of a structure. For example, in a home, the elements coincide with the floors, pillars, walls, etc.
  • Systems: are a set of components associated to form an element or to perform a function. For example, the roof system consists of tiles, insulation, vapor barrier, beams, etc.
Image showing a graphic scheme explaining the organization of the tables in the UniClass 2015 classification system

Graphical scheme explaining the organization of the tables in the UniClass 2015 classification system

So the UniClass 2015 system is based on tables. Each of these tables relates to a specific informative aspect and can be used individually or combined with other tables to express more complex concepts.

Here are the main titles and contents of the various tables.

AForm of informationThe documents are classified either based on the type of content (catalogs, price lists, etc. ) and the media (magazines, videos, etc.).
BSubject DisciplinesThe disciplines related to the world of construction.
CManagementConcepts related to decision making.
DFacilitiesCivil engineering works.
EConstruction EntitiesThe concepts relating to buildings, pavements, bridges and viaducts.
FSpacesThe concepts relating to building spaces, regardless of whether they are internal or external.
GElements for buildingsThe concepts relating to the elements in place belonging to the world of building production.
HElement for civil engineering worksThe concepts relating to the elements in place belonging to the world of civil engineering.
JWork Section for buildingsA classification complementary to that of construction works focused on the “work sections “.
KWork section for civil engineering worksA classification complementary to that of civil engineering works focused on the “work sections “.
LConstruction productsThe products of construction.
MConstruction aidsThe equipment of the construction site.
NProperties and characteristicsThe properties of the entities subject to classification.
QUniversal decimal classificationComplex concepts, which can be determined by combining different class-specific codes.

Between 2013 and 2015 the UniClass 2015 classification tables from 15 were reduced to 11.

Table 1CoComplex (complessi)Project as a whole (villa, university campus etc.)
Table 2EnEntities (Entità)Buildings according to function
Table 3AcActivities (attività)The activities that are carried out within the spaces
Table 4SLSpace/Locations (spazi)The spaces (the premises that make up the building)
Table 5EFElements/Function (Elementi/Funzioni)The elements are the single main components of a building (walls, foundations, roofs, etc.)
Table 6SsSystems (sistemi)The set of components of an element (the panels and uprights of a plasterboard wall, the joinery and carpentry elements that make up a door, etc.)
Table 7PrProducts (prodotti da costruzione)
Table 8TETools and Equipment
Table 9ZzCADThe concepts related to computer science applied to construction
Table 10FIForm of Information
Table 11PMProject Management

An element is identified by:

  • 1 pair of alphabetic letters referred to the table
  • 4 pairs of numbers that identify groups, subgroups, sections and objects.

In the next paragraph I’ll also show you how to classify any entity (for example a roof, a wall, etc.) of an IFC model.

You can try to classify the elements of any 3D model yourself (IFC, DWG, SKP, etc.), using usBIM.viewer + for free. Just open any file, (here you can download an example file) and select the ” Edit ” button in the ” Classification ” section of the ribbon bar.

Color image showing IFC and building classification systems and an example of UniClass 2015 classification with usBIM.view +

IFC and building classification systems | Example of UniClass 2015 classification with usBIM.viewer +


image showing the dialog to select the subgroups of the UniClass 2015 classification in usBIM.viewer+

UniClass 2015 classification in usBIM.viewer +

How to classify IFC entities with usBIM.viewer +

The IFC standard also uses classification systems to catalog the entities of a project and implement the information system associated with them.

How can I actually add new classifications in the IFC language?
Below I show you a practical example to classify a project entity with usBIM.viewer +, according to the UniClass 2015 system.

Simply follow these steps:

  • download and install viewer+ for free;
  • click on File > Open and select the IFC file to upload;
  • to modify the model click on Edit IFC > Edit;
  • select (manually or with the help of selection groups) the objects to add a classification;
  • from the toolbar, in the Select Classification section, click on Edit;
  • from the dialog, select the type of classification, in our case UniClass 2015 (October 2018 version ), and then the subcategories to be associated with the selected entity;
  • then click on confirm;


IFC and building classification systems - animated GIF on how to set up IfcClassificationReference in usBIM.viewer+

Setting  IfcClassificationReference in usBIM.viewer+


As illustrated in the animated GIF, after selecting the interested entity, you can read the information you just assigned in the right toolbox of the Properties:

  • IfcClassificationReference expresses the code to which the type of information we have added corresponds
  • IfcClassification expresses the type of classification adopted (in this case UniClass 2015).

For further information, here’s the IFC File example which you can download for free to view a project cataloged according to the UniClass classification system.

In this way you can check the classification assigned to each entity by following these simple steps:

  • open the IFC file with usBIM.viewer +
  • select an entity (e.g. a door, a wall, an attic, etc.)
  • read the classification information in the right toolbox of the Properties:
    • IfcClassificationReference shows the code
    • IfcClassification expresses information on the type of classification system adopted (in this case UniClass 2015).

Remember that since this is not a standard, it is always necessary to reach agreement in advance between the different role players involved the type of classification to be adopted, in order to make the exchange of information univocal.