The effect of juvenile wood and lay-up practices on various properties of radiata pine laminated veneer lumber

Laminated veneer lumber (LVL) was produced in seven different configurations, including current industry practice, all juvenile, all mature, mixed juvenile and mature, deep lathe check, and an alternative lay-up, which glued the loose face to the loose face, and a control. The all juvenile lay-up did not decrease the stiffness (E-p min) of the LVL significantly compared to many other patterns. The juvenile wood component seemed to perform at least as well as current industry practice. The juvenile LVL was found to have more twist and bow, and no difference in crook compared to the mature lay-up pattern. The deep lathe checks did not decrease the stiffness of the LVL, but did show an increase in distortion compared to most of the other lay-up configurations. The alternative configuration of matching the loose face to the loose face increased the average stiffness of the resulting LVL studs. It also had significantly lower crook and bow, although this alternative lay-up did increase the amount of twist. Overall, the LVL fell within allowable parameters of distortion according to the governing lumber-grading rules. For twist, 90 percent of the LVL studs were below 2.5 mm, one-fourth of the allowable limit of 10 mm. For both crook and bow, over 99 percent of the studs were below one-fourth of the allowable limits of 10 mm and 20 mm, respectively. The radiata pine veneer produced a median structural grade of F5, and 93 percent of the studs were F5 and better. There were no F11 studs found in the LVL. The amount of reject material was low: 2.9 percent of the total number of studs.