Description of defects by type for six grades of red oak lumber

Defects in hardwood lumber affect the grade assigned to the lumber. This study focused on the frequency and size of the various defect types as related to the lumber assigned to the various lumber grades. The study involved 13,253 board feet (BF) of red oak lumber in six grades, FAS, F1F, SEL, 1C, 2C and 3AC, and determined the average size of each defect type per occurrence, the average area occupied by each defect type per BF, and the average number of each defect type per BF. Stain, wane, and decay were found to be major defects with regard to defect size per occurrence. Decay was found to be less important to the lumber grades than the other two defects because it occurred relatively infrequently. Size per occurrence of mineral streak, holes, splits, grub holes, and worm holes did not differ between lumber grades. Checks, knots, and bark pockets, however, generally were smaller per occurrence in FAS, F1F, and SEL than for the 1C, 2C, and 3AC lumber grades. Wane and stain were the major defects when the defect area per BF was analyzed. Knots, checks, decay, and holes were found to be of intermediate importance. Bark pockets, splits, mineral streak, grub holes, and worm holes were of minor importance. No significant difference was found in the area of major defect types between the FAS, FlF, and SEL lumber grades. Lumber grade 3AC showed the clearest impact of defect size with the significantly largest sizes of stain, wane, decay, knots, and checks. The three lower grades (1C, 2C, and 3AC) had significantly more wane than the higher grades. Wane, stain, and knots were the major defect types that appeared to differentiate 2C from 1C lumber. There were no significant differences in the area of major defect types between the FAS, FlF, and SEL lumber grades. The defect types with the most defects per BF were knots, checks, and wane. When all defect types are combined, FAS and F1F lumber did not differ from each other but did differ from the other lumber grades. SEL and 1C lumber did not generally differ from each other but differed from the 2C and 3AC grades. The 2C and 3AC grades differed significantly in numbers of defects per BF. The number of defects per BF were found to be an important indicator of lumber grade.

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