Written specifications are an integral part of every construction project manual. These specifications must adhere to the formats and standards of the Construction Specifications Institute in the USA, and Construction Specifications Canada in Canada. Specifications communicate the information required to achieve a desired work result.

There are four methods of specifying: performance, descriptive, reference standard, and proprietary. The different methods of specifying can be combined in a single specification section. Care needs to be taken when combining methods to specify a single product in order to avoid conflict and redundancy. In this article, we provide a basic overview of these four methods.  

Performance Specifications

Performance specifying focuses on the end result, and includes information for verifying the end result. There are no limitations on the method of achieving this result.  To be effective, a performance specification must clearly define the desired end result.  If this is not done, the project can suffer from a loss of quality control.  The end result should be somehow measurable through testing or evaluation. Descriptions of materials and processes should be minimal.  Performance specifying encourages innovation to achieve desired results.  

Performance specifying can be used in any specification. Performance specifications can be selected as a way to access a range of options using current technology.  It can also be used to invite innovation for technologies that are not yet developed or standard in the construction industry.

Descriptive Specifications

While descriptive specifications were once the preferred method of specifying, they are now used less often due to project complexity and increasing availability of reference standards. Descriptive specifications are detailed descriptions of the properties required of a material, product or piece of equipment. Detailed descriptions of workmanship required for installation are used.  For descriptive specifications, the burden of performance rests with the architect or engineer. Descriptive specifications are lengthy, and writing them can be an involved process. They may be chosen when proprietary specifying is not an option and reference standards are not available

Reference Standard Specifications

Industry standards are published by professional groups, trade associations, standards-writing organizations, institutions, and governments.  Industry standards are incorporated into reference standard specifications by reference to a number, title, or other designation.  Use of standards saves the task of writing text that would indicate the requirements of the standard.  The specification writer on a project should know the standard and incorporate it properly into the specification.  Additionally, the specification writer should be aware of potential pitfalls including that standards usually refer to minimum requirements, and inadequate reference standards exist and should be avoided. Once a reference standard is included in a specification, means should be provided to ensure the standards are being met. This can involve test reports, samples, on-site reviews, test reports, manufacturer's literature, and other submittals.

Proprietary Specifications

Selected products may be identified directly in proprietary specifications.  A specification is also considered proprietary even if a manufacturer’s name is not mentioned if the specified product is available from a single source. Proprietary specifications on construction projects allow for control of product selection.  This can reduce costs and save design time, and simplify the bidding process.  The drawbacks of proprietary specifications include reduced competition, or errors made in model or product designations. Closed proprietary specifications name a single product, or several as options and substitutions are not allowed. Open proprietary specifications permit for substitutions, but require approval of the architect or engineer. 

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For all methods, specifications must be written with care and attention to detail. Thorough research of products must be done prior to selection. Products need to be able to be tested or evaluated, as well as coordinated with other selected products.