I-joists are prefabricated ‘I’ shaped engineered wood structural members, using sawn or structural composite lumber flanges and OSB webs, bonded together with exterior type adhesives. I-joists are ideal for long spans, including continuous spans over intermediate supports and especially suitable for floor and roof framing in both residential and non-residential construction.
American producers mainly supply I-joists in lengths up to 60 feet, and the most common depths, in inches, are 9-1/2, 11-7/8, 14 and 16. Each manufacturer provides technical material specific to their own product. For example, APA member mills produced this construction guide for I-joists here.
In the EU and UK, there is no standard for I-joists. To obtain a mark of conformity, each manufacturer must first apply for a European Technical Assessment (ETA) to measure the product against specific test requirements.This leads to a European Assessment Document (EAD) which is currently accepted by the EU and UK construction. More on EAD.