Unifying Uniclass

Proposed changes to the UK construction sector's classification system, Uniclass, are outlined by John Gelder, Head of content development and sustainability at RIBA Enterprises.

Uniclass: Unified classification for the construction industry (1997) is promulgated by Construction Project Information (CPI) , an organization comprising representatives from RIBA, RICS, UKCG, ICE, CIBSE, CIOB and CIAT. Uniclass is a voluntary classification, but is called up in BS 1192:2007, which is in turn called up in BIM: Management for value, cost & carbon improvement . Its use is therefore endorsed by the Government. It comprises 16 Tables, several of which were created using existing (legacy) classifications (e.g. CAWS, EPIC, CI/SfB Table 0). Uniclass is closely aligned to ISO 12006-2:2001 .

1. Problems with Uniclass

In spite of its publication subtitle, Uniclass is not unified. The Tables differ in many ways:

• Scope – some Tables cover architecture (buildings and landscape) and civil and process engineering, but others only deal with one or two of these sectors. For example, Table F only covers architectural spaces, and Table K only covers work sections for civil engineering (though some of these overlap with those in Table J). See Table 1. The dots indicate emphasis in each Table
• 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). See Table 2
• Depth – the Tables are not consistent – some comprise up to seven levels (Tables D, L and M), one (Table K) has just two, for example. See Table 2
• 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. See the red levels in Table 2
• 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.

Table 1: Uniclass Tables – scope

 
Table 2: Uniclass Tables – coding, depth and placement

 
The Tables should align, but they do not. For example, the Tables for elements, work sections and products should align, so that work sections can be used to map designed elements (aka systems) to their component products, i.e. in the project specification. Consider building services (Table 3): the terminology, sequencing, grouping and coding are inconsistent between the three Tables. This is simply because they were independently developed.

Table 3: Uniclass Tables – poor correspondence

 
Some objects do not have Tables in Uniclass. For example there are no Tables for high-level objects such as 'districts' and 'infrastructure', and there are no Tables for 'activities' or 'systems'. Though 'construction aids' have a classification Table, aids for design and documentation (e.g. simulation software, drawing boards, master specification systems) do not.

Some Tables offer several alternative approaches for classification without plumping for any particular one. Table E is reasonably clear about civil entities, for example, but for buildings it offers several alternatives within the one subgroup – including by form, by relationship with adjoining buildings, and by special form of construction. It does something similar for bridges. ISO 12006-2 provides for alternative approaches to the classification of entities, but it does this using separate Tables. Interestingly, classification by function – a feature of ISO 12006-2 – is not dealt with in Uniclass at all.

Perhaps because it predates it a little, Uniclass does not align perfectly with ISO 12006-2. But then, neither does the US OmniClass  (see Table 4). However, the general feeling is that the ISO itself is not perfect (e.g. Gelder, August 2011), so misalignment is not necessarily a criticism of Uniclass.

Table 4: Mapping to ISO 12006-2

 
In spite of the endorsement in BS 1192, some of the Tables see little use, there being little demand at present (though this might change as we move to Building Information Modelling [BIM]). However, in some cases, their underuse arises because other classification systems have been preferred by UK industry. For elements, for example, RICS' Building Construction Information Service (BCIS) uses other classification systems for the New Rules of Measurement (NRM)  and Standard Form of Cost Analysis (SFCA)  (which are slightly different  from each other). For products, CI/SfB is still used by the RIBA Literature Classification Service  (alongside Uniclass Table L) and RIBA Product Selector  (though you can also search the NBS Plus products subset by Uniclass Table J Groups ), irrespective of the deficiencies identified in the Preface to Uniclass: Unified classification for the construction industry, and the fact that CI/SfB is no longer maintained.

BIM requires a unified approach to classification if it is to work well, e.g. with simple mapping between classification Tables – current Uniclass is not unified at all.

2. 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
• The development of an online classification request tool  – 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 complete overhaul of Uniclass, including the Work sections Table (Gelder, November 2011), 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 by Easter 2012. 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, and that the Work sections Tables should be combined. New Tables will also be developed in this tranche, e.g. for Activities, Systems, Phases 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. However, the work by NBS will only develop the architectural components of the Tables, leaving room for civil and process engineering, which are to be developed by others
• Coding: All Tables will use numeric coding below level 1. This means that the familiar alphanumeric CAWS codes (e.g. H45) must 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. Decimalization won't be used (though users might apply it, e.g. in project specifications)
• Depth: All Tables will have four levels, where possible, and five levels otherwise. The four levels would be:
  •  Table, e.g. 25
  • Group, e.g. 30
  • Subgroup, e.g. 65
  • Object (product, space, element etc), e.g. 88.
  An object code might then be 25-30-65-88, for example. For an application where it is obvious which Table is being used, the first code could be dropped, e.g. in a specification system, which would use only the Work sections Table. NBS does this at present, using H45 rather than JH45 for example.
• Object placement: All Tables will set individual objects at the lowest level. Higher levels are for groups and subgroups of objects. The elements and systems Tables may include a lower level, for 'sub-objects', i.e. sub-elements and subsystems (see below)
• 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 a very much simpler object than the other.
  • Alignment: Tables will be structured so that they align with each other, and their terminology revised so that it is consistent. 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. See below
• New Tables: These 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. See below.
  • 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 Fittings, furnishings and equipment [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 about to be revised (the first meeting of the reconvened ISO/TC59/SC13/WG2 is on 13-14 December 2012), and the author will be involved in that process, but whether we will be able to influence the outcome so that the revised 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.

Alignment

The proposed new Uniclass Work sections Table is the armature for Table-to-Table alignment (this article assumes you are familiar with the structure of the Work sections Table – see Gelder, November 2011). The table below (Table 5) shows how this armature function would work.

The Work sections Table includes sections for systems. The Table does not include the systems themselves, however. These would be held in the project specification. Logically, the proposed new Uniclass Systems Table would have a parallel classification of systems. The Systems Table can exactly parallel the Work sections Table down to the third level. Below this (Level 4 in the Uniclass Systems Table), the actual systems listed in the Systems table would be those described in system outline clauses in the project specification.

Similarly, the Work sections Table also includes sections for products. Again, the Table does not include the products themselves. These would be held in the project specification. Logically, the proposed new Uniclass Products Table would have a parallel definition of products. The Products Table can exactly parallel the Work sections Table down to level 2. Below this (Level 3 in the Uniclass Products Table), the actual products listed in the Products table would be those described in product clauses in the project specification. Product sections are likely to have a subsection structure, which would need to be included here, pushing the Products themselves down to Level 4. This has yet to be resolved.

Table 5: Uniclass Work sections Table as armature

We can achieve similar mapping for regions, districts, facilities and so on, between the new Uniclass Work sections Table (which includes sections for these objects) and the corresponding Uniclass Regions, Districts, etc Tables. We can perhaps even align the administrative components of the Uniclass Work sections Table (Group 00 Project management) with the corresponding Uniclass Management Table. The extent to which this is possible, or practicable, will become clearer as NBS undertakes the development work commissioned by CPI.

The armature function of the Uniclass Work sections Table has another aspect, which is that it indirectly supports mapping between the various object Tables, as indicated in the diagram below (Table 6). Mapping is not the function of the Uniclass Tables, but it is the function of the specification, which is structured using the Uniclass Work sections table. For BIM, this mapping function is critical, so that all objects are connected through the object hierarchy, viz:

• Sites (facilities) comprise Buildings and grounds
  • Buildings and grounds comprise Systems
    • Systems comprise Products
      • Products comprise Components.

Table 6: Uniclass Work sections Table as mapping tool

This suggests that Tables in Uniclass that define objects by composition, in terms of the next objects down the chain (e.g. Systems composed of Products), are not needed. The outline clauses in the Work sections are more suited to providing this. They can also cover all 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 could, however, map the object to classes of sub-objects, which in this case 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

New Tables

This is the proposed list of tables, in their proposed order, which is rather different to that in current Uniclass. Tables in red are new to Uniclass. Three of these are found in the US OmniClass  – Phases, Roles and Services.

Documents and management

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

Objects

• 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.

Work section structure (Gelder, 2006) and Work sections are intimately connected. For example, the Work section structure might be such that everything about a system is described in the section, as is the intention with the revised Uniclass. Or this might not be so, in which case some aspects of a system will need other sections to describe them, as is the case with the North American MasterFormat (Table 22 in OmniClass) and SectionFormat (not part of OmniClass). In other words, work sections cannot be classified without reference to their internal structure.

Phases correspond to the RIBA Plan of work, but there are other phase classifications in use in the UK, for which CPI has prepared a mapping. A generic classification across all sectors would be useful. Roles are independent of Disciplines – architects may have a design role, but also roles as contract administrator, CDM coordinator, access consultant, or BREEAM certifier. Or, others might take on some or all of these roles. Exchange of information is intended to pick up current table Z, extending it beyond CAD protocols to full BIM.

Regions and Districts are high level objects of interest to planners, but also to landscape architects and civil engineers. Infrastructure – the stuff that connects and serves Sites (facilities) – is one of the realms of the civil engineer. Infrastructure straddles Regions and Districts, and some Sites are a part of Infrastructure, e.g. water treatment plants.

Activities currently do not have an explicit table of their own – they are dealt with as a faceted sub-table within the current Table N, Properties and characteristics, e.g. N41:D83 Sleeping. Faceting is supposed to be used between Tables, not within them, so this is not a satisfactory solution – hence the new Table.

Systems are rather different to Elements, which is a term that tends to have different meanings to different audiences, e.g. quantity surveyors vs. manufacturers. In design of buildings we refer to Air conditioning systems, Signage systems, Foundation systems and so on. Systems are what are described in specifications and on drawings, then, and it is worth making the distinction between them and Elements (which have a strict ISO 12006-2 meaning as something un-designed and so only capable of being characterised by function).

Contractors provide many Services, as do other players in the construction project, quite apart from constructing a building. For example, PFI-type contractors may be engaged to provide 'soft' FM services such as catering and laundry during the occupancy phase. If the main construction contractor doesn't do this, then specialist FM contractors will. Construction professionals also provide a range of services. A classification for Services is clearly needed.

Increased usage of Uniclass, decreased usage of alternatives

CPI's classification request tool will help make the Uniclass Tables living tools, rather than static ones, encouraging user participation in classification and use of the new Tables. NBS needs to switch to the new Uniclass within its products and services, such as RIBA Product Selector and NBS Plus, and needs to phase out its use of alternative classification systems. Using the new Uniclass in NBS Create should be quite a significant driver of change. Indeed NBS Create can serve as a partial proxy for the project specification in the development of these Uniclass Tables.

CPI and NBS need to:

• Encourage external agencies (e.g. WRAP, BRE Green Guide) to move to the new Uniclass for the classification of their products and services
• actively promote the new Uniclass on its merits, of which coherence and suitability for BIM will be the most significant.

It is expected that CPI member organizations will be sounding out their memberships regarding the proposals for change to Uniclass, where this is considered appropriate. They should of course adopt the new classifications themselves, in their products and services. Educational activities on the changes outlined in this and related articles will be key – CPI and NBS hope to hold joint workshops in Manchester and London, in late February 2012.

References

BS 1192:2007 Collaborative production of architectural, engineering and construction information – Code of practice.

BIM Industry Working Group, BIM: Management for value, cost & carbon improvement, Strategy Paper, July 2011.

CPIC (Marshall Crawford et al, eds), Uniclass: Unified classification for the construction industry,  RIBA Publications, 1997.

Gelder, John, 'Standard section structure', NBS Journal 9, November 2006.

Gelder, John, 'Some thoughts on ISO 12006-2', ICIS Newsletter, August 2011.

Gelder, John, 'The new Uniclass Work sections Table', NBS Journal 19, November 2011.

ISO 12006-2:2001 Building construction – Organization of information about construction works. Part 2: Framework for classification if information.