Impact of log sweep on warp in southern pine structural lumber

Almost 14 billion board feet of southern pine lumber are used each year in the United States for new construction or renovation of existing buildings (16). The incidence of warp in structural grades of southern pine lumber is high (4). As a result, a high proportion of pieces may be underutilized or discarded at the job site. Recent research indicates that warp within structural grades of softwood lumber may not be attributable to measurable growth characteristics in the lumber (4,8). This study investigated the impact of one log growth characteristic, sweep, on warp in southern pine 2- by 6-inch (38 by 140 mm) lumber. Results showed that both bow and crook in lumber sawn from sweeped southern pine logs were significantly greater than were bow and crook in lumber sawn from straight southern pine logs. Mean bow, crook, and twist in the study lumber were substantially lower than grade limits for No. 2 structural joists and planks. It may be reasonable to expect more lumber sawn from sweeped, southern pine logs to be underutilized or discarded at the job site because of warp compared to lumber sawn from straight southern pine logs.

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