Knots and Timber Defects

Knots are the most common natural structural features found in sawn timber, representing the internal portions of branches that became progressively encased within the main trunk as the vascular cambium deposited new annual rings of wood over time.

In wood technology and timber grading, knots are fundamentally categorised into two types based on the living status of the branch at the time of encasement. A live knot, or tight knot, occurs when a living branch is integrated into the trunk; its wood fibres remain physically continuous with the surrounding stem wood, ensuring it remains firmly fixed in the processed board. A dead knot, or loose knot, forms when the tree encases a dead branch stub. Because the branch is no longer growing, its fibres are completely disconnected from the trunk, resulting in a dark, resinous ring that often causes the knot to fall out entirely during sawmilling, leaving an open hole.

Knots significantly disrupt the straight alignment of wood grain, creating localised zones of grain deviation that severely compromise the timber's tensile and bending strength. Consequently, managing knot formation through silvicultural techniques—such as maintaining high planting densities to encourage natural self-pruning or executing timely manual interventions such as high pruning—is essential for producing high-grade structural timber and flawless decorative veneer.