Production specification

3. Production specification generally

3.1 Introduction

3.1.1 Definition of production specification

The term 'specification' can mean type of process, information, or document:

• Specification process: an inherent part of the design process, it consists of determining and communicating the nature and quality (as distinct from geometry, size and shape) of each element, system, type of work, product, etc.
• Specification information: written and numeric description resulting from the specification process.
• Specification document: a document consisting principally of specification information.

The specification process is independent of the form of contract used and who employs the various designers who contribute to it. Under traditional forms of contract most of the specification process will be pre-contract, but with forms that involve design by the contractor much of it will be post-contract.

Specification information is produced and used at all stages of design and construction, and may be included in many types of document, e.g.:

• The client's design brief will include functional, space and performance requirements, cost limits, and perhaps also preferences for certain materials or components.
• Financial analysis statements or cost plans need to state the products, systems and other assumptions allowed for under each elemental category.
• Design drawings and reports for presentation to the client need to confirm the main products, finishes, methods of construction and services systems.
• Submissions for statutory approvals need to describe relevant aspects of the proposed construction relating to appearance, health and safety, thermal efficiency, etc.
• The production documents (drawings, specification, bill of quantities if used, schedule of work if used) describe the nature and quality of the work that the constructor is required to provide.
• Instructions issued to the constructor during the course of the works give additional specification information to clarify or, in some cases, to vary the production documents.

At the early stages of a project the specification information will be mainly in terms of the required performance. During succeeding stages it becomes increasingly prescriptive.

This Code of Practice is concerned with production specification, which is defined as: 'written information prepared by the design team for use by the construction team, the main purpose of which is to define the products to be used, the quality of work, any performance requirements, and the conditions under which the work is to be executed.'

3.1.2 Relationship between production specification and drawings

A drawing consists principally of graphic information, it's primary purpose being to show by means of lines, graphic symbols and dimensions the size, shape and location of the building and it's parts. Drawn information and specification information are therefore complementary, and the relationship between the two should be kept clear and simple.

Descriptive annotation on drawings can give rise to problems, and should be minimised by systematic cross-referencing to the specification document - see the recommendations of this Code in Section 2.2.3. A key convention in this is the Common Arrangement of Work Sections (CAWS), described in greater detail in Section 4.1.2.

Location schedules are traditionally included in sets of production drawings, giving the details and locations of ironmongery, finishes, sanitary fixtures, etc. The essential reason for this information being regarded as drawings is that it's 'matrix' format invariably required it to be on large sheets of paper.

The information on such location schedules is usually production specification information (see definition at 3.1.1 above) and should, logically, be included in the specification document. If the information is formatted with some forethought, it can and should be given on A4 paper as part of the specification or schedule of work, removing the need for 'drawn' schedules.

The way this is done will depend on several factors, but particularly the size and complexity of the project and whether a specification (see Section 4.1.4) or a schedule of work (see Section 5.1.5) is used.

3.1.3 Purposes of production specification

Production specification (in conjunction with drawn and measured information) should define the quality of the systems, products, workmanship and finished work such that all parties can have a reasonable degree of confidence that:

• The designers' detailed requirements will be met.
• The work can be priced with certainty and accuracy.
• Products can be ordered correctly and in good time.
• The work can be planned, executed and supervised in a controlled manner.
• Misunderstandings and unintended variations are minimised.

3.1.4 Attributes of good production specification

Production specification should be:

• Specific to the project, with no irrelevant material.
• Comprehensive, covering every significant aspect of quality to a degree of detail appropriate to the importance and nature of the work.
• Practicable, requirements being specified having regard to the nature of the project and the available knowledge and resources.
• Constructive, in other words helpfully specific, so that all parties know what is expected.
• Technically correct and up to date, reflecting current good building practice and current statutory requirements.
• Enforceable, requirements being specified only if compliance can be demonstrated economically and within an acceptable timescale.
• Well coordinated, with no conflicts or ambiguities, either within itself or with drawings and measured information.
• Developed throughout the project lifecycle, to become an essential part of the as built information.

3.1.5 Use of language

Specifications should be clearly and economically worded – the objective is to transfer information from designers to constructors with speed and certainty. Clarity and simplicity of style can save time for both specifier (when editing a basic text) and constructor.

Brevity can be achieved by using an economical style, judicious use of specification by reference, and saying only that which needs to be said, for example:

• Do not repeat things covered in the standard conditions of contract or the project preliminaries.
• Do not repeat information already specified by reference to another document.
• Do not anticipate remote contingencies by lengthy provisions.
• Use generic description rather than a range of examples.
• Avoid special emphasis as it rarely helps and can imply that other things are not important.
• Leave out 'justificatory' explanation; however where the reason for a requirement may not be clear to the constructor, it may be helpful to state it.

3.1.6 Standards of specification practice

The CPI Production Specification Code 1987, Section 2, described the historical background, current standards, and objectives for future development of UK specification practice. In general, UK specification practice failed to meet the attributes listed in Section 3.1.4, and contributed little to the efficiency of the construction process and the quality of the built product. It was generally recognised that:

• On larger projects, 'architectural specification', produced by the quantity surveyor as 'preambles' to bills of quantities, was usually inadequate in coverage, over-generalised, and not very useful.
• Engineering specification was invariably bulky, often unreasonably onerous and restrictive, with needless variety of technical content and presentation.
• On smaller projects, schedules of work were often produced as the prime specification document, but were extremely variable in form and content, hence of questionable usefulness and reliability.
• On all types of project, it was normal practice to copy text from previous projects, with little checking, so that the specification was invariably out of date and often inappropriate for the project.
• There was a high incidence of discrepancies and divergences between notes on drawings, descriptions in bills of quantities and the information in preambles/specification.
• In consequence, specifications were held in low repute and mostly ignored, with buildings being constructed from the drawings, bill of quantities descriptions and post-contract instructions. The inadequacies of specification information were a frequent source of claims.

Specification practice in the UK compared very unfavourably with practice in other countries, particularly North America. The need to improve standards was widely recognised, and was seen to depend on the creation of an industry Code of Practice and the development and widespread adoption of suitable specification writing systems.

The 1987 CPI Project Specification Code and the development and uptake of the National Building Specification (NBS) have since underpinned a widespread improvement in specification practice on large and medium size projects. However specification systems suitable for small projects and building services have not been available or have not been widely taken up.

Sections 3, 4 and 5 of this CPI Code provide updated and extended guidance to prompt further developments in specification practice. Particular emphasis is placed on the use of suitable computer aided specification writing systems and other currently available IT resources that offer major potential benefits.