The compressive strength in psi for Douglas Fir and Southern Pine when perpendicular to the grain is what value?

• A. 250 psi
• B. 750 psi
• C. 1000 psi
• D. 500 psi

Answer: (D)

Compression perpendicular to the grain is where the wood crushes across the fibers, which is much weaker than loading along the grain. For Douglas Fir–Larch and Southern Pine, the standard value used for this perpendicular-to-the-grain compression is about 500 psi. That makes sense because across the grain the cell structure can’t effectively transfer the load, so the capacity is limited to roughly this level. Values much lower or higher than this don’t align with how these species behave in this orientation, and real-world factors like moisture, grain quality, and defects can reduce it further, but 500 psi is the typical design approximation students memorize for these woods.