What Are The Types Of Specification In Civil Engineering Projects?

Technical requirements may be specified in different ways, depending on what best meets the client’s requirements. One or more of the following types of technical specifications may be used for a building project.

Descriptive Specifications. These describe the components of a product and how they are assembled. The specification writer specifies the physical and chemical properties of the materials, size of each member, size and spacing of fastening devices, exact relationship of moving parts, sequence of assembly, and many other requirements.

The contractor has the responsibility of constructing the work in accordance with this description. The architect or engineer assumes total responsibility for the function and performance of the end product. Usually, architects and engineers do not have the resources, laboratory, or technical staff capable of conducting research on the specified materials or products.

Therefore, unless the specification writer is very sure the assembled product will function properly, descriptive specifications should not be used.

Reference Specifications. These employ standards of recognized authorities to specify quality. Among these authorities are ASTM, American National Standards Institute, National Institute of Standards and Technology, Underwriters Laboratories, Inc., American Institute of Steel Construction, American Concrete Institute, and American Institute of Timber Construction.

An example of a reference specification is: Cement shall be portland cement conforming to ASTM C150, ‘‘Specification for Portland Cement,’’ using Type 1 or Type 11 for general concrete construction. Reputable companies state in their literature that their products conform to specific recognized standards and furnish independent laboratory reports supporting their claims.

The buyer is assured that the products conform to minimum requirements and that the buyer will be able to use them consistently and expect the same end result. Reference specifications generally are used in conjunction with one or more of the other types of specifications.

Proprietary Specifications. These specify materials, equipment, and other products by trade name, model number, and manufacturer. This type of specification simplifies the specification writer’s task, because commercially available products set the standard of quality acceptable to the architect or engineer.

Sometimes proprietary specifications can cause complications because manufacturers reserve the right to change their products without notice, and the product incorporated in the project may not be what the specifier believed would be installed. Another disadvantage of proprietary specifications is that they may permit use of alternative products that are not equal in every respect.

Therefore, the specifier should be familiar with the products and their past performance under similar use and should know whether they have had a history of satisfactory service. The specifier should also take into consideration the reputation of the manufacturers or subcontractors for giving service and their attitude toward repair or replacement of defective or inferior work.

Under a proprietary specification, the architect or engineer is responsible to the client for the performance of the material or product specified and for checking the installation to see that it conforms with the specification. The manufacturer of the product specified by the model number has the responsibility of providing the performance promised in its literature.

In general, the specification writer has the responsibility of maintaining competition between manufacturers and subcontractors to help keep costs in line. Naming only one supplier may result in a high price. Two or more names are normally supplied for each product to enhance competition.

Use of ‘‘or equal’’ should be avoided. It is not fully satisfactory in controlling quality of materials and equipment, though it saves time in preparing the specification. Only one or two products need to be investigated and research time needed to review other products is postponed.

Base-Bid Specifications. These establish acceptable materials and equipment by naming one or more (often three) manufacturers and fabricators. The bidder is required to prepare a proposal with prices submitted from these suppliers. Usually, base-bid specifications permit the bidder to submit substitutions or alternatives for the specified products.

When this is done, the bidder should state in the proposal the price to be added to, or deducted from, the base bid and include the name, type, manufacturer, and descriptive data for the substitutions. Final selection rests with the client. Base-bid specifications often provide the greatest control of quality of materials and equipment, but there are many pros and cons for the various types of specifications, and there are many variations of them.

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