Uniclass2 – Why and How?

Proposed changes to the UK construction sector’s classification system, Uniclass2 – why and how

Adopting Building information modelling (BIM) for managing information from concept to grave means sharing information with the right people at the right time. Ensuring that information is structured the same way by all interested parties requires a unified approach to classification. It is also important that the classification is unified so that at each stage of the life cycle of any construction project information can be developed in a logical manner. The current UK standard classification, Uniclass, consists of a number of tables that provide a good framework but it is not well aligned for mapping from one table to another. This document identifies the issues and sets out the proposals for improving and unifying Uniclass.

Current Uniclass

  • Scope – some Tables cover architecture (buildings and landscape) and civil and process engineering, but others only deal with one or two of these sectors – Table F only covers architectural spaces for example, and Table K only covers work sections for civil engineering (though some of these overlap with those in Table J).
  • Coding – most Tables use numeric coding below Level 1, but two use alpha-numeric coding (Tables J and K). Most respect the ‘limit of ten’, but some use double figures at some levels on an ad hoc basis (e.g. Tables F and L).
  • Depth – depth of the Tables is not consistent – some Tables comprise seven levels (Tables D, L and M), one (Table K) has just two, for example.
  • Object placement – Tables J and K place the objects they are classifying at the same (lowest) level throughout, but the other Tables may place objects at any of two to five levels. That is, in some Tables a given level may be used both for groups of objects and for individual objects.
  • Granularity – in some Tables the lowest level objects differ markedly in ‘scale’, in others they are more consistent. For example, in Table D oil refineries (D165 3) and signal boxes (D116 1) are classed as ‘facilities’ with no further subdivision.
  • Alignment – the tables do not align completely because they were independently developed. Component products do not clearly map to their elements.

Unifying Uniclass

CPI established its Uniclass Working Group in 2006, to consider various industry proposals for revision of the Tables in Uniclass. This has resulted in a number of Stage 1 outputs. These include the release of a new Table, Z, for CAD, an online layer-generating tool for AutoCAD DWG and Bentley MicroStation DGN CAD systems, and the development of an online classification request tool. This tool is an indication of how far CPI has come in embracing the idea that classifications need to be dynamic, responding to industry needs.

Stage 2 entails the overhaul of Uniclass, including the Work sections Table to address the issues outlined above. NBS proposals for Phase 2 were accepted as the basis for industry consultation by the Uniclass Working Group, and then by CPI itself on 30 September 2011. NBS has now been commissioned by CPI to deliver the first tranche of unified Uniclass Tables. Tables under review in this first tranche include those for Facilities (D), Construction Entities (E), Spaces (F), Elements (G and H), Work sections (J and K) and Products (L). It has been agreed that the Elements Tables should be combined (i.e. an elements table for construction rather than one for building and one for civil engineering), and that the Work sections – now Work Results – tables also should combine building and civil engineering projects. New Tables have also be developed in this tranche, e.g. for Activities, Systems, and Work section structure.

Taking the issues described above in turn, here are the current Phase 2 proposals:

  • Scope: All Tables will cover architecture (buildings and landscape), and civil and process engineering.
  • Coding: All Tables will use numeric coding below level 1. This means that the familiar alphanumeric CAWS codes (e.g. H45) will go. Coding for level 1 (Tables) will be revisited, but may be numerical also. All level codes in all Tables will be double-digit, from 00 to 99 potentially.
  • Depth: All Tables will have four levels, where possible, and five levels otherwise. The four levels would be


Numbering system
Level Example
Table Ee
Group 30
Subgroup 65
Object 88


An object code might then be Ee-30-65-88, for example.

  • Object placement: All Tables will set individual objects at the lowest level. Higher levels are for groups and subgroups of objects.
  • Granularity: Objects within a given Table (i.e. at the lowest level) will have similar granularity. There are obviously limits to this, e.g. both bricks and doorsets are manufactured products, and would be listed in the lowest level of the Uniclass Products Table, but one is very much simpler than the other.
  • Alignment between Tables: Tables will be structured so that they align, and their terminology revised so that it is consistent between Tables. If possible, coding will be matched across Tables, though it is expected that this will only be possible in part. For alignment between Tables, the Work sections Table will be pivotal.
  • Missing Tables: Tables will be created for missing objects such as Activities. The Tables will be sequenced to reflect the project timeline, as far as this is appropriate.
  • Alternative approaches to classification: Each Table will deliver just one, complete, approach to classification. In particular, function will be used as a unifying approach to the classification of higher level objects (from Regions down to Spaces, and to FF&E systems – based on the current Uniclass table D), e.g. Agricultural regions, Agricultural districts, Agricultural facilities, Agricultural buildings, Agricultural activities, Agricultural spaces, and Agricultural FF&E systems.
  • Alignment to ISO 12006-2: Ideally the unified Uniclass would align to a revised ISO 12006-2. However, this might not be possible. The ISO is going to be overhauled, and we hope to be involved in that process, but whether we’d be able to influence the outcome so that the ISO aligns with the new unified Uniclass remains to be seen. The unifying Uniclass timeline is such that the project cannot wait for a revised ISO 12006-2.