Wood Strength Tests and Lumber Sizes

Wood strength depends on how its fibers are aligned along the length of the tree. This alignment gives wood much greater tensile strength along the grain than across it, sometimes up to twenty times higher. Wood also tends to perform better under compression than under tension.

Fiber length varie...

Wood fibers align along the tree's length, giving it up to twenty times higher tensile strength along the fibers than across them. Wood is also generally stronger in compression than in tension.

Hardwoods have fibers around one twenty-fifth inch long, while softwood fibers range from one-eighth to one-third inch.

The strength prope...