Which lumber defect is characterized by a lengthwise grain separation between or through the growth rings?

The lumber defect characterized by a lengthwise grain separation between or through the growth rings is known as "shake." This defect occurs when the wood fibers separate along the growth rings, often due to stress or changes in moisture content. Shakes can weaken the structural integrity of the lumber and may affect its appearance and usability, especially in construction where strength is critical.

Understanding this defect is important for contractors and builders, as it can impact the choice of materials and the overall quality of a construction project. By recognizing shakes in lumber, professionals can make informed decisions that ensure the safety and durability of their structures.