The expected performance of a prefabricated wood I-joist is dependent upon the quality of the material used in its production and the quality of the production process.
Because each manufacturer is likely to use a different material source and a different production process, custom production procedures must be established.
Moreover, the quality of material purchased for the manufacture of wood I-joists varies and therefore a quality assurance program that monitors daily production, and independent third party quality audits conducted by an accredited certifying agency on a regular basis are necessary.
Before commercial production begins, each manufacturer's product must be extensively tested to determine the engineering properties. Once production is started, a random sample of product is frequently selected for testing to ensure the manufacturing materials and processes meet prescribed strength values.
Prefabricated wood I-joists are proprietary products having engineering qualities dependent on the materials and flange joints used and production process variables. Therefore designers and installers follow the design guidelines as well as the installation guidelines of the individual manufacturers.
The Canadian Construction Materials Centre (CCMC) has issued product evaluations for many of the prefabricated wood I-joists marketed in Canada.
In the United States, the International Conference of Building Officials (ICBO) has published a document titled Acceptance Criteria for Prefabricated Wood I-Joists, for evaluation of these products. The Council of American Building Officials (CABO) has issued product evaluations for I-joists.
The recent ASTM Standard D5055, Standard Specification for Establishing and Monitoring Structural Capacities of Prefabricated Wood I-Joists, outlines procedures for establishing strength values and controlling the quality of prefabricated wood I-joists.