Last edited 28 Sep 2016

Working drawing

Production information is '...the information prepared by designers, which is passed to a construction team to enable a project to be constructed' (ref CPIC The importance of production information). Production information is incorporated into tender documentation and then the contract documents for the construction works.

Production information may include:

Working drawings provide dimensioned, graphical information that can be used; by a contractor to construct the works, or by suppliers to fabricate components of the works or to assemble or install components. They may include architectural drawings, structural drawings, civil drawings, mechanical drawings, electrical drawings, and so on.

Traditionally, working drawings consist of 2 dimensional orthogonal projections of the building or component they are describing, such as plans, sections and elevations. These may be drawn to scale by hand, or prepared using Computer Aided Design (CAD) software. However, increasingly, building information modelling (BIM) is being used to create 3 dimensional representations of buildings and their components for construction. This may be described as a virtual construction model (VCM) and can comprise a number of different models prepared by different members of the project team.

Working drawings may include title blocks, dimensions, notation and symbols. It is important that these are consistent with industry standards so that their precise meaning is clear and can be understood. Specification information can be included on working drawings or in a separate specification, but information should not be duplicated as this can become contradictory and may cause confusion.

The scale at which drawings are prepared should reflect the level of detail of the information they are required to convey. Different line thicknesses can be used to provide greater clarity for certain elements.

It is important that the purpose of the drawings and the people that will use them are considered. Working drawings might be prepared for; statutory approvals, for contractors to plan the construction works, to provide instructions on site, for the procurement of components, for the preparation of shop drawings, for the appointment of subcontractors and so on.

Drawings must be structured carefully so that they convey necessary information to carry out particular parts of the works. To give greater clarity, they may be separated into packages, so that information is specifically tailored to separate parts of the works, specific components, or separate suppliers or trades. It may be necessary to produce some packages earlier than others, for example, for items with long manufacturing times such as switchgear, chiller units, lifts, escalators or bespoke cladding systems, or for front-end construction such as service diversions, demolition, setting out details, underground drainage, piling and groundworks.

The quality of production information is extremely important. Unless it is prepared and co-ordinated properly, there will be disputes and delays on site, and costs will be incurred. Common problems with working drawings include:

  • Poor co-ordination of information.
  • Errors and omissions.
  • Information not getting to the right people.
  • Poor presentation.

Responsibility for the preparation of production information will depend on the selected system of procurement and the chosen form of contract. On traditional contracts (and management contracts and construction management contracts), production information may be produced by a consultant team, working for the client. Some specialist elements of production information may be produced by specialist contractors, co-ordinated by the lead designer. On other forms of contract, such as design and build, responsibility for preparing and co-ordinating production information may lie with the main contractor.

Working drawings may be updated when the works are complete to show ‘as constructed’ information, reflecting changes to the works that may have occurred during the construction process.

Carefully prepared working drawings can be very beautiful and the very best have been exhibited as works of art.

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