I-Joists
Engineered wood beams and I-joists are an excellent alternative to sawn lumber for floor joists due to their strength and lower installation costs. Wood I-beams resemble steel beams and consist of a center section constructed out of a thin layer of Oriented Strand Board (OSB) material that is sandwiched on top and bottom by two wide flange sections made out of finger jointed sawn lumber. Typically there are cut-out or knock-out sections in the OSB material that can be removed for running electrical wires and heat ducts.
Engineered wood beams are much stronger, straighter and stiffer than conventional sawn lumber. Data indicates that they are 50% stiffer than sawn lumber, so they provide less deflection. Because of their unique construction wood I-beams do not warp, shrink, cup or twist and thus they are able to create stiffer floors that have fewer tendencies to settle or squeak.
As a result of their strength, wood beams can be used to cover larger spans and can be separated on wider on-center spacings. Engineered wood beams are also much lighter than conventional sawn lumber, weighing up to 60% less than their sawn lumber counterparts.