In this article from 2012, John Gelder here considers the Uniclass parent standard, ISO 12006-2, now being revised. John is on the ISO/TC 59/SC 13/WG 2 externallinkTask force, as the UK expert (reporting to BSI committee B/555 externallink). Its first meeting was held in December 2011.

This standard – ISO 12006-2:2001 externallink Building construction – Organization of information about construction works – Framework for classification of information – has been implemented in several national classification systems (e.g. BSAB 96 externallink – Sweden, Uniclass externallink 1997 – UK, DBK 2006 externallink – Denmark, NS 3451:2009 externallink Table of building elements – Norway, and OmniClass externallink 2011 – USA and Canada). This experience has suggested some ways the ISO could be improved. Here we look mostly at the UK Uniclass experience.

There are four issues explored briefly here. The first is that the standard does not offer a single definitive framework for classification. The second is that the sequence of tables does not correlate very well to the project sequence. The third is that a number of objects do not have tables at all. Finally, we look at the idea that we need tables that classify objects by their composition. Any changes made to the ISO should of course be reflected in Uniclass.

The standard

The sequence, objects and terminology vary a little throughout the document, which is confusing. There are at least three versions, as the table indicates. So we are forced to ask, just which version is the standard? Tighter editing would fix this. The Task force agreed that the standard should be consistent.

Section 3 Section 4 Table 1 Annex A
3.3a Construction result
Construction entity Construction entity – form A.1 Construction entities by form
  Construction entity – function or user activity A.2 Construction entities by function or user activity
Construction complex Construction complex A.3 Construction complexes
Space Space – degree of enclosure A.4 Spaces by degree of enclosure
  Space – function or user activity A.5 Spaces by function or user activity
Construction entity part Construction entity part -
- - A.6 Facilities
Element Element A.7 Elements
Designed element Designed element A.8 Designed elements
Work result Work result A.9 Work results
3.3b Construction process
Management process Management process A.10 Management processes
Work process Work process -
Construction entity lifecycle stage Construction entity lifecycle stage A.11 Construction entity lifecycle stages
Project stage Project stage A.12 Project stages
3.3c Construction resource
Construction product Construction product A.13 Construction products
Construction aid Construction aid A.14 Construction aids
Construction agent Construction agent A.15 Construction agents
Construction information Construction information A.16 Construction information
3.3d Property/ characteristic Property/ characteristic A.17 Properties and characteristics

Project sequence

Objects at different levels in the hierarchy are resolved at different stages in the project timeline, e.g. complexes are resolved at master planning, products at specification. It makes sense, then, for the object sequence to match their corresponding timeline sequence. But the sequence of the ISO tables does not match the basic project timeline (as in the RIBA's Plan of Work – see the next table). In particular, entity and complex should be swapped throughout. The Task force agreed that the tables should be rearranged to better match the timeline of a construction project.

RIBA Plan of Work ISO 12006-2
  Construction result Construction resource
  A.3 A.1/A.2 A.4/A.5 A.7/A.8 A.9 A.13 A.14
Construction complex
Construction entity
Work result (traditional)
Construction product
Construction aid
A Appraisal              
B Design brief              
C Concept              
D Design development              
E Technical design              
F Production information              
G Tender documentation              
H Tender action              
J Mobilisation              
K Construction to practical completion              
L Post Practical completion              

Missing tables

A glance at the Uniclass and OmniClass tables suggests some that are missing in the ISO (e.g. materials and roles – see next table). Other missing tables include activities, design aids and districts. We also need to ensure that the classification framework, including examples given, encompasses architectural, landscape, civil and process engineering projects. The Task force agreed that some possible tables are missing from the standard, and will undertake a web survey to determine industry needs for classification tables. This survey will be hosted by bips, the Danish sister organization to NBS.

ISO 12006-2 Uniclass Tables OmniClass Tables
A.1 Construction entities by form E Construction entities 12 Construction entities by form
A.2 Construction entities by function or user activity - 11 Construction entities by function
A.3 Construction complexes D Facilities -
A.4 Spaces by degree of enclosure F Spaces 14 Spaces by form
A.5 Spaces by function or user activity   13 Spaces by function
(Construction entity parts) - -
A.6 Facilities - -
A.7 Elements G and H Elements 21 Elements (includes Designed elements)
A.8 Designed elements -  
A.9 Work results J and K Work sections 22 Work results
A.10 Management processes C Management 32 Services
(Work processes) -  
A.11 Construction entity lifecycle stages - 31 Phases
A.12 Project stages -  
A.13 Construction products L Construction products 23 Products
A.14 Construction aids M Construction aids 35 Tools
A.15 Construction agents B Subject disciplines 33 Disciplines
    34 Organizational roles
A.16 Construction information A Form of information 36 Information
A.17 Properties and characteristics N Properties and characteristics 49 Properties
- P Materials 41 Materials
- Q Universal Decimal Classification -

A suggested set of tables for a future iteration of ISO 12006-2 is as follows:

Documents and management

  • Work sections
    • Work section structure
  • Management
  • Phases
  • Disciplines
  • Roles
  • Form of information
  • Exchange of information.


  • Regions
  • Districts
  • Infrastructure
  • Sites (i.e. facilities or complexes)
  • Buildings, landscape and other entities
  • Activities
  • Spaces
  • Elements
  • Systems (= designed elements)
  • Products
  • Materials
  • Properties and characteristics
  • Services – including 'soft' FM
  • Aids – design, documentation, construction, operation and maintenance etc.

Doubtless this is not a complete list, hence the need for a survey. The classification of objects by function and by form needs to be picked up where relevant. This means that for many objects there would be at least two tables. However, it is suggested that classification by function makes most sense – matching functions can be assigned to objects all through the hierarchy, e.g. Agricultural regions, Agricultural districts, Agricultural sites, Agricultural buildings, Agricultural activities, Agricultural spaces, right down to Agricultural FF&E systems and Agricultural FF&E products.

Other sub-classifications might be considered, e.g. spaces by degree of enclosure, work sections by trade or discipline, products by principal material, and buildings etc by size, principal form of construction, or relationship with adjacent buildings.


The Task force's view on compositional classification is that we should study the need for it further. In my view, the classification of objects by technical composition is not the job of a national classification system, but it is the job of a national master specification system. In NBS Create, for example, we provide compositional mapping between Buildings and their component Systems (we call this a Building outline specification), and between Systems and their component Products (we call this a System outline specification). The outline clauses can cover all technical permutations. For example, an outline clause for the 'Board suspended ceiling system' might have over 60 million product permutations (not all 'legal'). Attempting to cover all such permutations in preconfigured mappings is not viable (one of the limits of the BRE Green guide to specification externallink, for example).

One could, however, map the object to classes of sub-objects in a classification system, which in the case of a system could be called 'sub-systems', e.g.

Board suspended ceiling system

  • Suspension grid
  • Suspension grid fasteners
  • Insulation
  • Barriers in ceiling void:
    • Fire barriers
    • Acoustic barriers
    • Plenum barriers
  • Linings:
    • Inner layers
    • Face layer
    • Fasteners
  • Joint treatment
  • System accessories.

This is the sort of thing we are publishing as part of the NBS National BIM Library externallink, in part as a contribution to the development of IFC-compliant property sets. It may be that the classification table for Systems could be extended in this fashion to include sub-systems, though this would make it very lengthy. Something similar might be done for Elements, and some other object classes.

In later versions of NBS Create we will extend this compositional view of objects by providing mappings (in the NBS Create Work sections) between Sites and their component Buildings, between Buildings and their component Activities and Spaces, and so on. NBS Create is of course organized around Work sections, so provided they cover everything from Regions down to Materials (as they will in NBS Create), Work sections are therefore the key to tying all the tables (including those dealing with management) together through this compositional mapping. This is why they have been put at the top of the list.

This makes sense also because Work sections for modern forms of procurement may be needed as early as project inception, e.g. for full design-build procurement of a university campus or hospital. The Work sections therefore need to be able to describe performance and other requirements for Facilities (and higher-level objects), not just for traditional 'trades'. With this in mind, 'Work sections' need to be redefined as we extend the concept of 'work' to include anything a contractor (and this term should embrace the architect and other consultants) might do, including master planning, design and documentation. That is, 'work' includes design and documentation, which may be carried out by in-house client teams, consultants, and/or construction contractors and subcontractors. It also includes operation and maintenance, which again may be carried by in-house client teams, specialist contractors, and/or construction contractors and subcontractors. For more on this role of the Work sections table, refer to the article 'Unifying Uniclass'.

About this article

A shorter version of this article was published in the ICIS Newsletter externallink, August 2011.