Structural timbers are wood pieces larger than 4X6, used in framing and structural construction. Structural timbers are manufactured from second and third-growth timber, for the most part.
Structural timbers are evaluated visually, mechanically or else they are scanned digitally, with grades assigned on the basis of each member’s strength, not only its appearance. Grading rules for structural timber limit imperfections that affect strength. The structural timbers are then graded, according to species and size. Each species and grade is assigned different values for its usage.
Species Combinations of Structural Timbers
Certain western species of timber share properties as far as performance. These types of structural timbers are grouped together. This makes marketing easier, and allows further design values of structural timbers to be developed. That way, structural timber can be assigned according to species combination, rather than kinds.
Structural timbers usually are bought, sold, and specified for end use according to specific species combinations. Because of the durability of these woods, California redwood and the western cedars are generally marketed as distinct species of structural timbers.