Prefabricated wooden I-beams are engineered structural products used for floor joists and roof rafters. They are made in the shape of an “I” from two flanges of a structural wood product connected by a web of structural panel products (see diagram). I-beams offer an alternative to dimension lumber in floor joists (supports) and roof rafters but use as little as 50% of the wood that lumber would require, doing more with less.
Because of their composition, wooden I-beams can be produced to meet a wide variety of performance standards. The material used for the flanges (e.g., machine stress rated lumber, laminated veneer lumber or oriented strand lumber) and web (e.g., plywood, oriented strand board) as well as their size can be chosen to meet the requirements of particular uses. I-beams are lightweight, very uniform and not prone to warping. Their relatively light weight means that they can be installed manually, although special connectors are required because of the cross-sectional shape of the beams. Holes for electrical, plumbing or mechanical services may be pre-punched or drilled through the web, but the size, number and location of the holes must follow the manufacturer’s recommendations.
Most I-beams are used for flooring and roof support in residential construction throughout North America. While I-beams have been used for roof rafters, concrete-forming elements and wall studs, the majority of I-beams are used as floor joists.
I-beams are used for floor support in about half of all new houses built in North America. This market share changes little from year to year. Growth has flattened out and is now tied to new house construction and repair and remodelling.
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