Performance specified work in construction contracts
Specifications vary considerably depending on the stage to which the design has been developed, ranging from performance (open) specifications that require further design by the contractor, to prescriptive (closed) specifications where the design is already complete when the project is tendered.
Most projects involve a combination of performance and prescriptive specifications. Items crucial to the design may be specified prescriptively (such as external cladding) whilst less critical items, or items requiring specialist design may be specified only by performance (such as service lifts).
Performance specifications describe the result that is required from particular items and leave it to the contractor or supplier to satisfy that requirement. In effect it requires them to complete the design. The nature of the performance required is typically defined by the desired outcome, or by reference to standards. See Performance specification for more information.
Performance specified work is increasingly common as buildings become more complex and the supply chain becomes more integrated, with contractors and suppliers having greater involvement in design at an earlier stage of the project.
Performance specified work used to be most commonly defined in a ‘contractors designed portion’ as a supplement to the main contract, but increasingly now it forms part of the requirements of the main contract itself.
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