What is a lengthwise grain separation in lumber called?

A lengthwise grain separation in lumber is called a shake. This occurs when the wood fibers separate along the growth rings, typically due to factors such as natural forces during the tree’s growth or improper handling during logging or drying. Shakes are often characterized by their long, narrow fissures that run parallel to the grain of the wood. This defect can compromise the structural integrity of the lumber, making it important for contractors and builders to identify and account for such imperfections when selecting materials for construction or woodworking projects.

In contrast, a split refers to a full separation of the wood along its length, which is more severe than a shake. A check describes surface cracks that can occur in wood due to drying and do not typically run along the grain direction as shakes do. Warp is a more general term that describes any deviation from a flat or planar surface, including bowing, crooking, or twisting of the wood and is not specifically related to the grain separation seen in shakes. Understanding these terms is crucial for anyone working with lumber in construction or home improvement projects.