Last edited 02 Nov 2021

Specification for construction

Specifications describe the products, materials, and work required by a construction contract. They do not include cost, quantity, or drawn information, and so need to be read alongside other information such as quantities, schedules, and drawings.

Specifications vary considerably depending on the stage to which the design has been developed, ranging from performance specifications (open specifications) that require further design work to be carried out, to prescriptive specifications (closed specifications) where the design is already complete.

Having a prescriptive specification when a contract is tendered gives the client more certainty about the end product, whereas a performance specification gives suppliers more scope to innovate and adopt cost-effective methods of work, potentially offering better value for money.

Typically, performance specifications are written on projects that are straight-forward and are well-known building types. For more information, see Performance specification.

Whereas prescriptive specifications are written for more complex buildings. For more information see: Prescriptive specifications.

They can also be used in combination. Items crucial to the design may be specified prescriptively (such as external cladding) whilst less critical items may be specified only by performance (such as service lifts).

Key to deciding whether to specify a building component prescriptively or not, is considering who is most likely to achieve best value, the client, the designers or the contractor:

Specifications should be developed alongside the design, increasing in level of detail as the design progresses.They should not be left until the preparation of production information. By tender, they should describe every aspect of the building in such a way that there is no uncertainty about what the contractor is pricing.

Aspects of the works are generally specified by:

It should be possible to verify standards of products and workmanship by testing, inspection, mock-ups and samples, and documentation such as manufacturer's certificates.

Specifications should be structured according to work packages mirroring the separation of the works into sub-contracts. This makes it easier for the contractor to price and so may result in a more accurate tender. A standard classification system should be followed, such as Uniclass.

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For your country please check examples from major builders they normally have detailed examples that can be modified to suit for build.

Designing Buildings Anywhere

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