PerSPECtives: Methods of Specifying
Multiple methods have become traditional within the building industry. The Construction Specifications Institute's (CSI) Project Resource Manual (PRM) is a good resource to use to learn more about the methods of specifying that are covered in this article. Additional information on this subject awaits in the CSI-PRM, which can be ordered from the CSI website at www.csinet.org.
When selecting products, several decisions contribute to whether the final result will provide the desired functional performance. Specifications communicate these functional requirements. Tasks and factors include finding appropriate products for the application, the manufacturer of the product, the installation requirements of the product, the cost(s) of the product - initial, installation, and operational - and the operation and maintenance of the product, to name a few.
A product specification writer needs to be aware of how all of the salient characteristics of a product can be communicated to the contractor. A given specification method can help make the communication process more effective and actually less time-consuming, depending on the product in question.
Four MethodsDesigners can choose from four specifying methods as described by CSI: descriptive, performance, reference standard, and proprietary. Although the methods are distinctly different, their use can be mixed within a single project, depending on the product being specified and the objective of the specification. CSI exerpts about these methods are as follows.
Descriptive specifications: "A descriptive specification is a detailed, written description of the required properties of a product, material, or piece of equipment and the workmanship required for its installation. Proprietary names of manufacturers are not used."
Performance specifications: "A performance specification is defined as a statement of required results with criteria for verifying compliance, but without unnecessary limitations on the methods for achieving the required results. The end result, rather than the means to the end result, is specified."
Reference standard specifications: "Reference standards are incorporated into the specifications by referring to a number, title, or other designation. The provisions of standards so referenced become a part of the specifications just as though included in their entirety."
Proprietary specifications: "Proprietary specifications identify the desired products by manufacturer's name, brand name, model number, type designation, or other unique characteristics."
There are two types of proprietary specifications: closed and open. In a closed proprietary specification, only one product is named (although several products may be named as options), and there can be no substitutions.
In an open proprietary specification, prices are requested for specified alternative products, substitutions and cost adjustments may be proposed by the bidders, and products are allowed as substitutions after approval by A/E.
Using the Method to Get What is NeededWhen and why each of these various methods of specification should be used depends on a number of variables, which we will address in upcoming columns. The objective is to clearly, concisely, completely, and correctly specify what is required.
Although some may not like the idea of a "proprietary" product specification, the reality is that the proprietary specification method is used often. Many products are specified using a "basis-of-design" approach in which the designer uses a specific product as a reference during the design to ensure that something will indeed work. Then this product is specified and scheduled in the contract documents to give the bidding contractors an idea of the "basis-of-design." The contractor is generally free, within the guidelines of specifications, to provide acceptable products from other manufactures. In certain ways, the "basis-of-design" process is most similar to the open proprietary method of specification as described by CSI.
Whether you are an engineer, architect, owner, contractor, supplier, code official, or consultant, it is good to have a clear understanding of the various specification writing formats in order to be able to read and understand contract document specifications. ES