These, together with the production drawings, combine to form the legal documents describing the totality of the construction process. A specification is a written document prepared by members of the Design Team and provides fundamental information which, for various reasons, cannot be incorporated on the production drawings for a proposed project. It is an integral part of the design process because it describes the quality of work which is considered necessary during construction. Information for a specification therefore evolves during the preparation of the production drawings, and is subsequently issued in two main parts:
- l Preliminaries describe the legal contract through which the construction work is controlled, including insurances; the facilities to be provided by members of the Building Team on site; the general conditions of the site and/or existing building to be converted, including details of access routes, roads and local restrictions; and other details concerning the general running of a project, including information about the quality of work required, nominated subcontractor and suppliers, hours of working, generation of noise, dust, etc.
- Trade clauses describe the actual construction methods (materials and techniques) to be adopted and may be done in the following ways:
- precisely describing the materials to be used and the work to be executed under each trade describing the materials and work required for each separate part or element;
- giving a performance specification (statement of requirement) which accurately details the quality of work expected in terms of performance criteria for each part involved, without describing a method of achieving it, e.g. Concrete in foundations, C15 (15 N/mm2). BS EN 206-1: Concrete. Specification, performance, production and conformity.
The purpose of a specification is to provide information to the potential builder or contractor of a proposed project which, together with the drawings, will enable a reasonably accurate price to be submitted or tendered for the work involved. The detailed information it provides could not be adequately indicated on the production drawings because these would become far too complicated, and extremely difficult to read. In order to avoid unnecessary confusion, it is important that notes on a drawing should not duplicate clauses of specification. Drawing notes should only provide a general comment necessary for an overall understanding, and which leads to the more detailed description in the specification. Only for very simple projects involving few trades will drawing notation suffice for describing the work; the legal arrangements are left to the clauses of the formal building contract