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Performance Specifications

Introduction

"Performance Specification" is one of the more misused terms in the construction industry as almost all specifications include a mixture of both prescriptive and performance items. If you are considering specifying any criteria by performance, there are three essential requirements. The criteria must be:
Achievable (There is no point in specifying the impossible.)
Measurable (The criteria must be quantifiable not qualitative.)
Verifiable (There must be a method of measuring the actual performance, e.g. by testing).
Some good guidance on the relative merits of performance and prescriptive specifications is provided in Section 3.2.2 of Production Information : A code of procedure for the construction industry.

The Guide was published, in January 2001, to an almost total lack of interest from the construction industry - hardly surprising considering that it is a very heavy, and essentially theoretical, document. Even the RIBA Bookshops website states "This publication is recommended to anyone seriously involved with performance specifications".
More recently, however, contractors have been asking architects to categorise performance-specified elements of a project in accordance with the JCT Guide. This is undoubtedly linked to contractors becoming more aware of their liabilities under contractual arrangements such as the Contractor Designed Portion Supplement (CDPS).
The JCT Guide categorises, in Appendix D, five levels of performance specification:
Level 1 : Prescriptive Specification (no design by Contractor)
Level 2 : Performance Specification (no 'in context' design)
Level 3 : Performance Specification (simple 'in context' design)
Level 4 : Performance Specification (complex 'in context' design)
Level 5 : Whole Building Performance Specification
Although the Appendix provides examples of "packages of work" which might be appropriate to each of the five Levels, it does not link these examples to the CAWS Work Section (as used by NBS and other proprietary specification systems) nor does it provide any specific guidance on the contractual arrangements most appropriate to each Level.
The JCT Guide is available from RIBA Bookshops.

The lists below, arranged by JCT Guide Level and CAWS Work Section, set out more detailed recommendations for determining which elements of the building may be designed, in detail, by specialists and specified in part, by performance. Note that these recommendations are constantly evolving as industry practice changes. You must read the notes to understand what actions you may need to take.

Although sometimes included in lists of specialist design, or performance specified work, the use of Clause 42, or the CDPS, is rarely appropriate for these items of work. Although they include elements of performance specification, the Contractor (or Sub-Contractor) is required solely to select an appropriate product from a manufacturer’s standard range and no ‘in context' design is involved.
K41 Raised access floors - JCT Guide says Level 3 (see below).
L10 Windows/rooflights/screens/louvres - Level 2 if proprietary.
L20 Doors/shutters/hatches - Level 2 if proprietary.
M22 Sprayed monolithic coatings - JCT Guide says Level 3 (see below).
M61 Intumescent coatings for fire protection - Not referred to in the JCT Guide.
P12 Fire stopping systems - Not referred to in the JCT Guide.
+ Any generic material specified by reference to a published standard, e.g. concrete blocks to BS 6073 : Part 1.
The JCT Guide includes raised access floors (K41) and sprayed monolithic coatings (M22) as Level 3 examples. Whilst, strictly speaking, there may be a small amount of 'in context' design, it is rarely appropriate to make any special contractual arrangements to cover these items of work.

Some, or all, of the work in the section may be designed by a specialist or specified by performance. If using JCT 98/05, this means the use of the CDPS or Clause 42 (Performance Specified Work). Read more about the limitations on the use of JCT Clause 42 below.
F30 Accessories for brick/block/stone/walling, e.g. windposts - Not referred to in the JCT Guide.
H31 Metal profiled/flat sheeting cladding.
H43 Metal composite panel cladding/covering.
H92 Rainscreen cladding.
K10 Plasterboard dry linings/partitions/ceilings.
K40 Suspended ceilings.
L10 Windows/rooflights/screens/louvres - Level 3 if purpose-designed.
L20 Doors/shutters/hatches - Level 3 if purpose-designed.
L30 Stairs/walkways/balustrades

All of the work in the section will be designed by a specialist. If using JCT 98/05, this is most likely to mean use of the CDPS. This is now generally accepted industry practice for these items of work.
G10 Structural steel framing
G12 Secondary structural steelwork
H11 Curtain walling
H13 Structural glass assemblies
H42 Precast concrete panel cladding
H51 Natural stone slab cladding
L35 Fixed utilitarian access systems
N25 Permanent access and safety equipment - Not referred to in the JCT Guide.
R10 Rainwater drainage systems (syphonic) - Not referred to in the JCT Guide.

There are significant restrictions on the use of Clause 42, as described in JCT Practice Note 25 (paragraphs 2.7, 2.8, and 2.10) and these restrictions are still not widely understood by many in the construction industry.
In particular, specifying an element of the works by "performance specification" does not automatically imply that this is "Performance Specified Work" (PSW), requiring the use of Clause 42.
The most significant restriction relates to the co-ordination of Performance Specified Work with work covered by the CDPS. Many believe that the contract (unamended) makes no provision for this and that Clause 42 is only suitable for work which interfaces solely with works prescriptively specified. Any work specified by performance which interfaces with CDPS works must also be covered by the CDPS to provide a contractual route for resolving the inevitable co-ordination issues.
These restrictions mean that, for many medium-large projects, the exclusive use of the CDPS will be preferable to a combination of CDPS with PSW.

Page last reviewed: 24/09/2007