Dwindling supplies of suitable sawn dimension lumber, as well as the roller-coaster movement of lumber prices, have led some form builders to use other framing materials to support formwork. Structural composite lumber (SCL), a precision-manufactured engineered-wood product, is an alternative that offers some of the same properties of wood along with enhanced strength and reliability. Like ordinary wood, the manufactured beams are workable and easy to handle, but they don't warp or twist, and they're 100% reusable. They reportedly cost less than aluminum and more than sawn lumber. However, they offer a greater return on investment, particularly when you consider that typically 20% or more of sawn lumber is discarded due to defects.
Three SCL products -- laminated veneer lumber (LVL), parallel strand lumber (PSL) and laminated strand lumber (LSL) -- are composites made of wood veneers or wood strands bonded under heat and pressure with an exterior-grade adhesive. The products come in a wide range of cross sections, including most of the sizes of sawn dimension lumber. Applications include formwork beams and joists, studs, wales, shoring and edge forms.
Wood I-joists -- another engineered-wood product -- often are used in prefabricated deck form panels. Typically, I-joists used in formwork are 10 to 20 inches deep with flanges up to 3 inches wide. However, joists up to 38 inches deep also are available.
