What is the timber defect that appears as cracks parallel to the grain on the surface?

What is the timber defect that appears as cracks parallel to the grain on the surface?

• A. Surface check
• B. Shake
• C. Split
• D. Warp

Answer: (A)

Surface checks are cracks that run parallel to the grain on the surface of timber. They form during drying when the outer layers shrink faster than the interior, creating tensile stresses that open thin cracks along the grain. These cracks stay at the surface and are usually shallow, making them a surface defect rather than a through-thickness failure. By comparison, a shake is a separation along the grain that can run inside the wood from one surface toward the opposite side; a split is a crack that extends through the entire thickness along the grain; warp refers to distortion like bow, cup, or twist rather than cracks.

Surface checks are cracks that run parallel to the grain on the surface of timber. They form during drying when the outer layers shrink faster than the interior, creating tensile stresses that open thin cracks along the grain. These cracks stay at the surface and are usually shallow, making them a surface defect rather than a through-thickness failure.

By comparison, a shake is a separation along the grain that can run inside the wood from one surface toward the opposite side; a split is a crack that extends through the entire thickness along the grain; warp refers to distortion like bow, cup, or twist rather than cracks.