Creating a value-added product using low-grade lumber produced from small-diameter timber would improve the economic balance for forest restoration operation. The general aim of this research was to increase or stimulate markets for wood products utilizing low-value small-diameter material generated in National Forest System restoration programs. Our hypothesis is that low-value lumber cut from small-diameter logs (4”-6” at the small end) could be successfully utilized in core layers of structural cross laminated timber (CLT) panels.
However, to be qualified for structural uses, CLT must meet standard minimum bond integrity criteria specified by the North American product standard (ANSI/APA PRG 320-2012), determined through laboratory testing for delamination (=5%) and shear resistance (=80% wood failure). The objective of this project was to determine the feasibility of small-diameter logs harvested from National Forest System restoration programs in 3- and 5ply CLT panels. Adding value to low-value timber harvested from USFS lands by using it within CLT applications is expected to increase profitability of the harvested timber, offsetting costs for the restoration programs. The specific objectives were to: (1) build and test CLT panels utilizing lumber from forest restoration operations in core layers of panels against the certification criteria per PRG 320-2012 to allow low-grade lumber in cores of structural CLT; (2) based on findings, propose respective changes to the current North American standard PRG 320-2012; and (3) investigate the efficiency of the primary processing of small-logs from the thinnings and lamination options with lumber produced from these small logs.