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 specifications in construction may be used for a building projects
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.
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 types of specifications in construction , 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.
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.