A structural, weight-bearing floor system is constructed by laying a floor deck across a number of underlying, supporting I joists. The deck may be made of a variety of different materials, with wood being particularly preferred in residential home construction.
Suitably strong and stiff wood joists are typically in the form of an “I joist.” An I joist has three parts: two flange members with an interconnecting webstock member. The I joist is constructed by creating a groove in each of the flange members into which the webstock member is inserted. In many applications, particularly for large scale commercial construction the I beams will be made from forged steel. However, in less-demanding applications such as the construction of residential and home construction, wood is often used because it costs less, is more easily cut, and doesn't require special fasteners can be easily adapted for use in residential and small-scale commercial buildings. While at one time all of these pieces were formed from solid wood lumber, recently they are more likely to be made from an alternative to solid wood lumber, engineered wood composites, because of both the cost of high-grade timber wood as well as a heightened emphasis on conserving natural resources. Plywood, particle board, laminated veneer lumber (“LVL”), oriented strand lumber (“OSL”), and oriented strand board (“OSB”) are examples of wood-based composite alternatives to natural solid wood lumber that have replaced natural solid wood lumber in many structural applications in the last seventy-five years. These engineered wood composites not only use the available supply of timber wood more efficiently, but they can also be formed from lower-grade wood species, and even from wood wastes.
However, in order to maximize the load that a composite wood I joist can carry, it is necessary to construct the I joist to match the somewhat complicated stress profile that an I joist experiences when a downward load is applied. In these circumstances, the stresses generated are distributed as compression along a top flange and as tension in the bottom flange.
Accordingly, there is a need in the art for an I joist that is constructed so that the top flange is composed of a wood composite material that is excellent at sustaining a compression load while the bottom flange is composed of a wood composite material that is excellent at sustaining a tension load.