BIM classification systems: GuBIMClass, AeasBIMClass, Uniclass and the rest

Why classify a BIM model

A BIM classification system is a common code that says what each object in the model is, regardless of the software, the language or what the modeller called it. For Revit, an element might be “Basic Wall: Generic 300 mm”; for the classification system, it is a code that any program, database or tender document understands in the same way.

That code is what makes it possible to:

• Take off quantities and cost by grouping elements into bill items without reviewing them by hand.
• Link the model to other systems: the maintenance CMMS, the asset register, the GIS.
• Automatically validate that the model meets the requirements: that every pump has its properties, that there are no unclassified objects.
• Search and filter: all the gate valves in a plant, all the suspended ceilings in a building.

If the model will only be used to produce drawings, classification matters little. If it is going to live with the asset —maintenance, management, digital twin—, it is what makes it useful.

The common framework: ISO 12006-2

Almost all modern systems are based on the ISO 12006-2 standard. It is not a classification system: it is the framework that says which tables one should have (by elements, by spaces, by products, by processes…) and how they relate to each other. Each country or sector then fills those tables with its own content. That is why the systems look alike in structure even though their codes do not match.

BIM classification systems in Spain

GuBIMClass · buildings

Created by GuBIMCat (Grup d'Usuaris BIM de Catalunya, the Catalan BIM user group) and presented in 2017; its reference version is 1.2. It starts from the Infraestructures.cat classification and draws on OmniClass, Uniformat, MasterFormat and Uniclass. It classifies by function, in three or four levels of digit pairs. Example: 40.20.10.10 — interior suspended ceilings.

It is free to use and the most widespread in buildings in Spain, although no state body imposes it as a general rule. Its documentation is published in the GuBIMCat repository.

AeasBIMClass · water cycle

The system for the urban water sector, developed by the BIM group of AEAS (now DAQUAS, the Spanish Urban Water Association, Asociación Española de Agua Urbana) with the coordination of Canal de Isabel II and some twenty organisations. Version 02, published in January 2025, has four tables: objects, processes, materials and fluids.

Each class carries a numerical code and a four-letter acronym. Examples from the table itself:

• AO.03.01.01.02.00 — gate valve (VVCM)
• AO.03.03.01.01.00 — horizontal centrifugal pump (BBCH)
• AP.08.04.02.00.00 — wastewater treatment plant, secondary settling (PRDS)
• AM.01.02.00.00.00 — reinforced concrete (MHAR)

It covers equipment, instrumentation and electrical systems, and expressly recommends combining it with GuBIMClass or SCFClass for civil works and buildings. Tables and guide on the AeasBIMClass v02 page. If you work with tanks, water treatment plants or sewer collectors —such as the Retamares tank or the Sant Feliu collector—, it is the system that makes sense.

SCFClass · rail

A system for the rail sector promoted by the Railway Innovation Hub, with a second version from 2023. It appears in ADIF tender documents; ADIF has required it in specific contracts to encode products in the model attributes.

RCEclass · state-owned roads

A multi-criteria classification of the State Road Network (Red de Carreteras del Estado), developed with Ineco. It was approved by Circular Order (Orden Circular) 5/2024 and is mandatory in all contracts with BIM requirements tendered by the Directorate-General for Roads (Dirección General de Carreteras). It is, to date, the clearest formal classification requirement of the General State Administration (Administración General del Estado).

If you have been told that “the Ministry requires GuBIMClass”, ask for the tender documents. The Spanish public procurement BIM Plan does not impose a specific system: each contract sets it in its tender documents, its BEP or the client’s manual. buildingSMART Spain summarises this in its guide to classification systems.

International classification systems

Uniclass 2015 · United Kingdom

Maintained by NBS and updated every quarter. It is the system that accompanies ISO 19650 in the United Kingdom and the one most requested by international clients. It is organised into tables identified by prefix —Ss systems, Pr products, EF elements, SL spaces, among others— and codes in pairs. Example: Ss_25_10_30_35, gypsum board partition systems. Free to consult at uniclass.thenbs.com.

OmniClass, UniFormat and MasterFormat · United States

Published by CSI (Construction Specifications Institute). OmniClass has 15 tables; its table 21 (elements) integrates UniFormat, organised by building systems, and table 22 (work results) integrates MasterFormat, the classic structure of North American specifications. Revit ships with OmniClass and UniFormat by default, which is why they appear in so many models even though nobody asked for them.

CCI and CoClass · Northern Europe

CCI (Construction Classification International) is based on the IEC/ISO 81346 standard and on the Danish and Swedish systems; since 2020 it has been managed by a non-profit association based in Brussels and is used by, among others, Estonia and Czechia. CoClass, from Svensk Byggtjänst, is the Swedish version. Its approach —describing assets as systems and components with reference designations— fits particularly well in infrastructure and asset management.

Quick comparison

How classification is stored in an IFC

In IFC, the open buildingSMART format, classification is not loose text in a property: it has its own entities.

• IfcClassification describes the system: name, version, publisher and location of the source.
• IfcClassificationReference stores the specific code (Identification), its name and, optionally, a link to its definition. It can point to another reference as its parent class.
• IfcRelAssociatesClassification links that code to one or more objects in the model.

Because an object can have several associations, the same element can carry codes from two systems at once. The full specification is in the IFC 4.3 documentation.

The typical mistake is to fill in the code in a Revit parameter and assume the IFC carries it correctly. If the export does not map that parameter to IfcClassificationReference, the code arrives as just another property and validators do not recognise it. It is worth opening the exported IFC in a viewer and checking; we review which ones in the guide to BIM viewers.

Classifying an as-built model

In a model that comes from a laser scan, classification has two particularities:

1. What exists is classified, not what was designed. An existing installation may not fit neatly into a class conceived for a new project. The criterion has to be decided and documented.
2. The point cloud is not classified, but the objects modelled on it are. That is why the list of categories to be modelled and their classification system should go together in the brief, as we explain in what is Scan to BIM.

In practice, what works is agreeing a simple table from the outset: modelling category → classification code → mandatory properties. With that, the model is classified from the start and does not need to be reviewed at the end. If your client has a BIM manual, we work to it; if not, we propose one based on the system that best fits their sector.