16 April 2020

Classification is needed in the construction industry. It was needed in a pre-BIM environment (an early example the Swedish Samarbetskomittén för Byggnadsfrågor, SfB, was launched in 1950), and it is needed even more in a BIM environment where the benefits of digital interoperability are likely to be huge. Over the years, this need for classification has resulted in a multitude of classifications, in different countries, across different disciplines, and even for the same purpose in the same place. This has reflected and reinforced professional and other information silos, frustrating efforts to coordinate, and now stymying digital integration.

Classifications have three levels of use. There are those who design, develop and maintain the classifications. There are those who apply the classifications to information about particular objects, such as manufacturers and model software developers. And then there are designers, specifiers, builders, maintenance workers and others who use the classifications assigned to the objects they are dealing with without knowing or caring where they came from. The author has operated at all three levels. But for most, object classification is ‘under the hood’. That does not mean that it is not important, and that an appreciation of it isn’t useful.

Classification tables

Individual unrelated classification tables are not enough. Current classifications in use in Australia in the construction industry include

  • the National Classification System (2019), published by NATSPEC; [1]
  • the classification used to structure the ANZ Standard Method of Measurement of Building Works (2018), published by AIQS and NZIQS (Australian and New Zealand Institutes of Quantity Surveyors, respectively); [2]
  • the North American OmniClass Table 22 Work results (2012), used by SpecPack; [3]
  • the project phases classification used in the Australian Institute of Architects Client architect agreement (2019); [4]
  • the property classification used to structure the Australian Building Codes Board National Construction Code suite; [5]
  • the property classification used to structure of the Green Building Council of Australia Green Star suite; [6] and
  • the buildings classification given in the ABCB’s NCC (2019). [7]

All seven classifications were developed independently of each other and do not align where they could – they were not intended to be interoperable. The first three are about the same object class – on a given project it is possible that all three could be used. In particular, it would have been useful if the first two aligned (NCS and the ANZ SMM), so Australian specifications could ‘talk to’ bills of quantities, and vice versa. This was the case in the UK some years ago. The NBS and NES national building specification systems and the RICS standard method of measurement used the same classification (Uniclass 1997 Table J Work sections for buildings), enabling interoperability. [8] But this has never been the case in Australia and, since RICS (Royal Institution of Chartered Surveyors) released the NRM (New Rules of Measurement) in 2012, it is no longer the case in the UK. [9]

Classification systems

A classification system is needed – comprising multiple tables, each for objects of different classes. Just one table, covering one object class, is not enough to serve many needs along the project timeline and across the various disciplines. The NCC partial Entities classification is useful at certain stages and to certain users (e.g. architects and other designers, building control authorities), but not to manufacturers and installers. The NCS likewise is useful at certain stages and to certain users (e.g. specifiers, quantity surveyors, subcontractors), but is not of much interest to planners or manufacturers.

The system must be coherent. An integrated sequence of coordinated tables is needed to create a coherent object hierarchy. This is especially the case for BIM, in which modelling essentially maps big things to little things. For example, it maps buildings to elements, elements to systems, and systems to products, and vice versa. Since each of these object classes will have its own classification table, it would make sense if they were designed with each other, and modelling, in mind. An incoherent collection of unrelated tables is not good enough.

None of the tables mentioned are part of a classification system of the kind outlined in ISO 12006-2:2015. [10] Current classification systems include OmniClass from North America, [11] CoClass from Sweden, [12] and Uniclass 2015 from the UK. [13] Table 1 shows how they correlate to the ISO and to each other. Only two might be regarded as coherent – CoClass and Uniclass 2015.

Table 1: ISO 12006-2 and three classification systems

ISO 12006-2



Uniclass 2015

A2 Construction information



Form of information

A3 Construction products







A4 Construction agents

Organizational roles






A5 Construction aids



Tools and equipment

A6 Management



Project management

A7 Construction process




A8 Construction complexes


Construction complex


A9 Construction entities

Construction entities by function

Construction entity


Construction entities by form



User activity [14]





Maintenance activities

Process activities (in development)

A10 Built spaces

Spaces by function

Built space


Spaces by form



A11 Construction elements


Functional systems



Constructive systems


A12 Work results

Work results

Work result

Redundant in Uniclass 2015 (see below)

A13 Construction properties





Since Australia has no such system of its own the question is: which of these classification systems should be adopted here, if any? The answer so far has been Uniclass 2015, though this adoption is in its early stages. Among major clients, the Office of Projects Victoria recommends it. [15] Transport for New South Wales (TfNSW) requires it and is actively engaged with NBS in its ongoing development. [16] The Rail Industry Safety Standards Board (RISSB) recommends it. [17] The use of Uniclass 2015 was recommended to Austroads in 2018. [18] Client adoption means that their supply chains will also use it, for civil works and for architectural works. However, most States have no requirements for classification in their BIM implementation guidelines. For example, SA does not stipulate an approach to classification, leaving this to the contractor [19] The relevant Queensland document makes no mention of classification. [20]

As for Australian BIM tools, NBS Chorus uses Uniclass 2015 as its ‘native’ classification system (others can be used). [21] The forthcoming NBS Source – for proprietary objects, their geometries and properties – will also use it as the ‘native’ classification system.[22] Autodesk Revit, Graphisoft ArchiCAD and Vectorworks 2020 SP3 embed Uniclass 2015 for objects linked to NBS Chorus. [23] Both NATSPEC and NZ Masterspec required that ‘BIM objects shall have a Uniclass 2015 classification assigned’ in the 2018 draft of the Open BIM Object Standard (OBOS), but this has been dropped in the published version. [24] However its use is supported (after a fashion) in the NATSPEC BIM Properties Generator, along with OmniClass and the NCS. [25]

Why Uniclass 2015?

OmniClass is comprehensive, but it is not current – the most recent official tables are dated 2012. The tables are not coherent – they were developed independently (e.g. MasterFormat and UniFormat) and then collected together to make OmniClass. Terminologies, sequences and groupings are different where they could be the same, making them difficult to use together in an integrated BIM environment.

CoClass is not comprehensive – it only has 9 tables. These are quite small so do not allow for the classification of many objects. The Components table, for example, could classify 17,576 objects if full. The Constructive systems table could hold 67,600 objects. This sounds a lot, but as they could never be anywhere near full for all sorts of practical classification reasons, it is quite a restriction on its future development.

Why are Australian organisations adopting Uniclass 2015? In terms of tables, Uniclass 2015 is more comprehensive than CoClass but less so than OmniClass, though other tables are planned (several have been drafted). The tables themselves serve all sectors and disciplines – since 2014 NBS has been working hard to expand the original architecture-focus to deal with transport and other sectors. Uniclass 2015 is current (most tables were updated in January 2020) and dynamic – updates are regular as the NBS team liaises with users, which is important to organisations such as TfNSW and VDAS. The tables in Uniclass 2015 are as coherent as they can be. For example, Complexes, Entities, Activities and Spaces all use the same basic classification – hence Co 45 Residential complexes, En 45 Residential entities, Ac 45 Residential activities and SL 45 Residential spaces. Finally, there is plenty of room within each of the tables for future expansion as required by industry for current and future needs. The Products table, if it was full, could classify 108 objects, though it currently classifies around 6800. The Systems table could also accommodate 108 object, and it currently classifies around 1500. All this room is needed to ensure adequate space around each object, for the addition of objects in the future. CoClass does not have this space for expansion.

One point to note for those who have looked carefully at Table 1 is that, in Uniclass 2015, the Work results table is considered redundant and will not be included. Mapping between object classes (e.g. Complexes and Entities) is properly done in BIM tools such as Autodesk Revit and NBS Chorus. Conventionally, Work results (or work sections) are used for mapping from Systems to Products, which is done in the Systems within NBS Chorus. Separate Work results sections would only duplicate this mapping. In the future in NBS Chorus, mapping from Complexes to Entities would be done in the Complexes ‘sections’ of what would be a ‘lifetime’ specification. And so on.

Perhaps a significant omission in Uniclass 2015 is the Properties table. Readers’ views on the need for this would be welcome. This would have to serve all the other tables, e.g. classifying properties for Products and for Activities. The properties assigned by BIM tools, geometric and otherwise, would all be classified, facilitating digital searching for compliant proprietary objects, or against attributes of interest such as flammability. Work on this table has commenced. Proposed tables beyond the ISO include Districts (or Precincts) and Regions (both in draft). These would allow Uniclass 2015 to be used to support Smart Cities initiatives. [26]

Where users insist on retaining an existing classification table or system, but others in a project are using Uniclass 2015, then two-way mapping will be needed. For the purposes of BIM, this should be able to be managed digitally, which requires simple 1:1 mapping. That is, an object in the existing table corresponds exactly to an object in Uniclass 2015, e.g. they both have ‘clay bricks’. However, for many objects this will not be the case. Instead we will find 1:many, many:1, 0:1, 1:0 and many:many mappings. All require human intervention to resolve, which is anti-BIM. To avoid this, ultimately everyone will have to use the same classification system, to ensure full interoperability, and to maximise the benefits of BIM. National adoption of a single classification system is good and international adoption is better.


A coherent classification system for construction is essential if we are to realise the full benefits of BIM. This is why the UK government ran a competition for the development of such a system in 2014, which was won by NBS with Uniclass 2015. As a result, Uniclass 2015 is now an official component of the UK BIM Framework, and promoted in BS EN ISO 12006-2:2020 (National foreword). ISO 12006-2:2015 in turn is mandated in ISO 19650-2:2018 (clause 5.1.7c), which has been adopted in Australia. [27] When we began this work, we thought it might only be used by NBS. But now we see the classification system being adopted very much more widely, including in Australia. The tables have been copied thousands of times worldwide. The adoption and implementation of Uniclass 2015 will expand into the future.


[1] NCS is free online at: www.natspec.com.au/resources/national-classification-system

[2] ANZ SMM is available to purchase online at: www.aiqs.com.au/imis/AIQS_Website/Shop/Books/AIQS_Website/Public/Shop/Books.aspx

[3] SpecPack is available to purchase at: https://specpack.com.au/

[4] These are: Concept design, Design development, Planning/Development Application, Construction documentation, Contractor selection, Contract administration. Also in use for project phases is the RIBA Plan of Work 2020.

[5] The NCC Volume 1 structure is: Structure, Fire resistance, Access and egress, Services and equipment, Health and amenity, Ancillary provisions, Special use buildings, and Energy efficiency.

[6] The Green Star Design & As Built structure is: Management, Indoor environment quality, Energy, Transport, Water, Materials, Land use & ecology, Emissions, and Innovation.

[7] NCC 2019 Volume 1 is free online at: https://ncc.abcb.gov.au/

[8] NES, the National Engineering Specification, has since shut down. UK services engineers have largely moved to the services engineering content produced by NBS and first published in 2004.

[9] The 3 volumes of RICS NRM are available to purchase online at: www.rics.org/uk/upholding-professional-standards/sector-standards/construction/rics-nrm-new-rules-of-measurement/

[10] ISO 12006-2:2015 Building construction – Organization of information about construction works – Framework for classification, ISO, Geneva.

[11] The OmniClass tables, including Table 22 mentioned above, are free online at: www.csiresources.org/standards/omniclass

[12] CoClass tables are free online at: https://byggtjanst.se/tjanster/coclass/

[13] Uniclass 2015 tables are free online at: www.thenbs.com/our-tools/uniclass-2015

[14] Identified in the ISO, but outside its scope.

[15] Office of Projects Victoria (2020) Victorian Digital Asset Strategy, Part C Application, pp71-73: “The VDAS recommends using Uniclass 2015, as it is ISO certified and a globally recognised and consistent system”.

[16] TfNSW (2019) Application of Uniclass 2015 for Transport for NSW, 6.2 Our decision: “TfNSW has selected Uniclass 2015, developed by the NBS … as the preferred classification system. The choice to adopt Uniclass 2015 follows comprehensive analysis of the current state, and comparative research of available classification systems, industry-wide, against ISO 12006.2:2015 …”.

[17] RISSB (2019) Digital Engineering: Code of Practice, Part 6.3 Project data classification: “This Code of Practice recommends the use of Uniclass 2015 as the adopted classification of assets and locations during the project lifecycle”.

[18] Austroads (2018) Asset data harmonisation Stage III: BIM IFC alignment review.

[19] Department of Planning, Transport & Infrastructure (2019) Project controls: Master specification – PC-EDM5 Digital engineering: “The DEXP [Digital Engineering Execution Plan] shall include the Contractor’s approach to … Asset Classification Matrix”.

[20] Department of State Development, Manufacturing, Infrastructure & Planning (2018) Digital enablement for Queensland infrastructure: Principles for BIM implementation.

[21] NBS Chorus (Australia) is available to purchase at: www.thenbs.com.au/

[22] NBS Source launches in the UK in April 2020: www.thenbs.com/nbs-source

[23] For the various NBS Plug-ins, see: www.thenbs.com/our-tools/nbs-plug-in-for-autodesk-revit

[24] OBOS is free online at: https://bim.natspec.org/documents/open-bim-object-standard

[25] The Properties Generator is free online at: www.propgen.bim.natspec.com.au/pages/178534.html

[26] The Smart Cities Council ANZ is at: https://anz.smartcitiescouncil.com/

[27] AS ISO 19650.2:2019 Organization and digitization of information about buildings and civil engineering works, including building information modelling (BIM) – Information management using building information modelling – Delivery phase of the assets, Standards Australia.