The 2021 IBC definition of cross-laminated timber describes a prefabricated engineered wood product consisting of not less than three layers of solid-sawn lumber or structural composite lumber. The adjacent layers are cross oriented and bonded with structural adhesive to form a solid wood element. Accordingly, option C is correct.
Cross orientation means that the principal grain direction of one layer is arranged approximately perpendicular to that of the adjoining layer. This configuration distinguishes CLT from products in which all laminations run parallel, such as conventional glued-laminated timber. The cross-oriented layup provides two-way panel behavior, dimensional stability, and structural capacity in both principal directions.
Option A is incorrect because CLT must contain at least three layers. Option B describes a mechanically laminated product rather than structural glued CLT; nail-laminated timber uses mechanical fasteners, whereas code-compliant CLT uses structural adhesives and must conform to the applicable manufacturing standard. Option D eliminates the defining cross-lamination characteristic and would instead describe a parallel-laminated product.
During inspection, the product label and certification documentation should be checked to confirm the panel was manufactured under the required quality-assurance program.
References/Topics: 2021 IBC Chapter 2 definition of “Cross-Laminated Timber”; Sections 602.4 and 2303.1.4; ANSI/APA PRG 320.
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