In Australian commercial construction projects, a "knot" refers to a unit of measurement used to quantify the number of timber boards or planks in a bundle. It is commonly used in the timber industry to describe the quantity of timber products being supplied or used in construction.

The term "knot" is derived from the practice of tying a knot in a piece of string to keep track of the number of boards in a bundle. In the past, when timber was manually counted and bundled, a knot would be tied in the string for each board, making it easier to keep track of the quantity.

In modern times, the term "knot" is still used as a unit of measurement, but it is more of a convention or industry standard rather than a literal knot in a string. A "knot" typically represents a specific number of boards or planks in a bundle, which can vary depending on the type and size of the timber being used.

For example, a bundle of 70x18mm (nominal size) hardwood flooring boards may contain 50 pieces per knot, while a bundle of 19x147mm (nominal size) pine decking boards may contain 40 pieces per knot. The number of pieces per knot can also vary depending on the supplier or manufacturer's specifications.

It is important to note that the term "knot" is specific to the Australian construction industry and may not be used in other regions or industries. In other parts of the world, different terms or units of measurement may be used to describe the quantity of timber products.

In structural grading, knots are considered a key factor in determining the stress grade of timber . The Knot Area Ratio (KAR) is used to estimate the impact of knots on the structural properties of timber, which requires a grader to visualize the knots going right through the cross-section .

A knot is typically considered significant if it exceeds one-third of the width of the timber, and/or if loose gum veins exceed one-quarter of the length, and/or if want and wane exceed one-quarter of the cross-section .

The presence and size of knots can impact the safety and quality of construction projects, and as such, it is essential to ensure that timber used in commercial construction projects meets the required standards and regulations.

References

• Structural grading is the process by which timber is sorted into groups, or stress grades, with ideally, similar structural properties in each group.
• They are estimated by the Knot Area Ratio (KAR) which requires a grader to visualise the knots going right through the cross-section. The KAR is the percentage ...
• A knot more than 1/3 of the width, and/or · Loose gum veins 1/4 of the length, and/or · Want & wane 1/4 of the cross section.