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Classification - an introductionOctober 2017

John Sands, Principal Consultant, BSRIA Sustainable Construction Group

With the drive towards more efficient ways of working within the construction industry, classification is a necessary tool for making sure that the vast amount of information about a building or asset can be accessed again when necessary.

In BG 68/2017 Classification – an introduction, the topic of classification is discussed in more detail. It defines what classification is and how it is used. It also gives examples of the classification status which have been, and are currently, used in construction. This article summarises BG 68 to give an introduction to classification and aims to show how useful it can be.

What is Classification?

Cambridge Dictionaries Online defines classification as:

‘The act or process of dividing things into groups according to their type’

Classification has been used in construction for many years, often without the users knowing it. For example, many mechanical engineers will recognise that a heading of ‘T31’ in their specification relates to ‘low temperature hot water heating’. This in fact came from a classification system called The Common Arrangement of Work Sections (CAWS) which covered architectural and MEP elements for construction projects. Using a system such as CAWS is to adopt classification – a structured way of naming or arranging information.

If there isn’t an agreed approach to naming things, it will be very difficult to find something again. One person may be using a naming strategy which is very obvious to them, but unfortunately it may not be as obvious to others.

The adoption of a classification structure or system enables information to be labelled systematically and provides a common language for all parties to use. This is becoming ever more important with information management as the key focus of BIM (building information modelling).

Examples of the types of information to be classified are:

  • Specifications
  • Product information/libraries
  • Drawings
  • Schedules of rates/quantities
  • Information management systems
  • Operation and maintenance information

Classification can also be used for applications other than physical attributes about a built environment asset. As well as classifying the various systems installed and the individual items of plant and equipment which form those systems, there can be benefits to classifying other aspects of the buildings such as spaces and activities.

What does Classification look like?


The most recognisable classification system used in construction in the UK is the Common Arrangement of Work Sections, generally known as CAWS. This is still widely used to identify various engineering systems and equipment within specifications and in drawing numbers.

Table 1 – CAWS (Common Arrangement of Works Section) example

CAWS is a group (or field) of up to three digits, representing increasing levels of detail as shown in table 1.

Here are examples of how it would look in specifications:

T31 Low temperature hot water heating

Other common CAWS classification codes are:

S10 Cold water
T10 Gas/oil fired boilers
T61 Chilled water
U12 Kitchen ventilation
V21 General lighting
V40 Emergency lighting
Y40 Air handling units


In a similar way to CAWS, New Rules of Measurement (NRM) is made up of three groups of digits which can be used to represent increasing levels of detail or granularity. It is used typically amongst cost consultants and wherever contractors for arranging information about cost and quantities.

When the three fields shown above are combined, the resulting code for Central Heating is:


Other common NRM classification codes are:

Table 2 – NRM (New Rules of Measurement) example

5.6.3 Central cooling
5.7.1 Central ventilation
5.8.3 Lighting installations
5.11.3 Lightning protection

Uniclass 2015

The growing presence of building information modelling (BIM) in construction has identified the need for a classification system which is more wide ranging in its scope. For the UK Government’s BIM Level 2 requirements, Uniclass 2015 has been developed as the chosen classification system.

Table 3 – Uniclass example

There are two significant differences between the two classification systems already covered here and Uniclass 2015. Firstly, Uniclass 2015 consists of a number of different tables, each dealing with a different aspect of the built environment. These are topics such as complexes, activities, spaces/locations, systems, products and project management. Secondly, it uses up to five pairs of characters to provide a classification code. These are shown in table 3.

The Products and Systems tables will be the most widely used for construction and asset management and cover most engineering elements which need to be classified in specifications and other forms of construction information.

The Uniclass 2015 classification code for low temperature hot water heating is:


Other common classification codes are:

Ss_60_40_17_12 Chilled water systems
Ss_65_40_33_51 Mechanical supply ventilation systems
Ss_70_80_33_35 Hard-wired general lighting systems
Ss_75_80_45_45 Lightning protection systems
Pr_60_60_08_33 Gas fired boilers
Pr_60_65_03_86 Supply air handling units
Pr_60_70_22_15 Consumer units

This article just touches the surface of what classification is, how it works and what it looks like. You can find out more details in BG 68/2017 Classification – an introduction.

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