Which orientation provides the greatest timber strength?

• A. Across the grain
• B. Perpendicular to grain
• C. Diagonal
• D. Parallel to the grain

Answer: (D)

Timber is strongest when the load runs along the grain because the fibers are aligned in that direction and can carry the stress more effectively. This alignment provides the highest tensile and compressive strength and stiffness, as the wood’s cellular structure works with the grain’s path. When the load is across the grain or perpendicular to it, the fibers must split and shear more easily, making the wood weaker. Diagonal orientation does not maximize the contribution of the fibers, so it isn’t as strong as parallel to the grain. Therefore, the greatest timber strength comes from parallel to the grain.