Construction Supervisor License Practice Exam

Which of the following factors does not affect the strength of lumber?

1. Shakes

2. Knots

3. Grain

4. Length

The correct answer is: Length

The strength of lumber is influenced by several physical characteristics and irregularities, while the length of the lumber itself does not directly impact its inherent strength properties. Shakes, knots, and grain all contribute to how lumber performs under stress. Shakes are separations in the wood that can lead to weaknesses, as they create areas where the wood can split or fracture. Knots are natural imperfections that can significantly affect the mechanical strength and structural load-bearing capacity of lumber, depending on their size and location. The grain, or the pattern of wood fibers, also plays a critical role in strength; straight grain is typically stronger and more durable than wavy or irregular grain. In contrast, while the length of lumber is essential in determining how it can be used in construction—such as its suitability for specific structural spans—it does not modify the material's internal strength. Thus, the length itself is not a factor that affects the strength of lumber in the same way that physical characteristics do.