Defects in timber Defects are blemishes in timber that reduce the quality and utility value of timber.

Defects in timber Defects in timber are categorized into two: Natural defects Artificial defects

NATURAL Defects in timber This occurs during the growth of the tree. Common examples are: Star shakes Heart shakes Cup or ring shakes Rind galls Knot Upset grain Cross grain

NATURAL Defects in timber STAR SHAKES These are radial splits which are wider on the surface and narrower as they move towards the centre.

NATURAL Defects in timber HEART SHAKES These are wide splits running right through the heart of a tree

NATURAL Defects in timber CUP OR RING SHAKES These are curved splits , separating one annual ring from the adjacent one either wholly or partly.

NATURAL Defects in timber RIND GALLS These are peculiar swelling or abnormal growth caused generally by the growth of layers of sapwood over wounds remaining after a branch of tree has been imperfectly cut off.

NATURAL Defects in timber KNOT They occur at the point where branch grow from the trunk of a tree. It at times rot away and fall out of position leaving what is called knot-hole

NATURAL Defects in timber UPSET GRAIN This occurs during growth or felling due to knocks it receives.

NATURAL Defects in timber CROSS GRAIN This occurs when the wood fibre does not align parallel to the axis of the piece of wood.

ARTIFICIAL Defects in timber DRY ROT This occurs as a result of fungi attack on the timber, thereby reducing the timber to a dry powder.

ARTIFICIAL Defects in timber WET ROT This is the decay of timber due to alternate wetting and drying

ARTIFICIAL Defects in timber CUP This is the concave curvature across the surface of the timber, resulting from bad stacking and shrinkage during drying.

ARTIFICIAL Defects in timber BOW This is either concave or convex curvature along the length of the plank.

ARTIFICIAL Defects in timber CHECK This is the separation of wood along the grain of the board.

ARTIFICIAL Defects in timber TWIST This is a spiral form of distortion along the length of the plank.

ARTIFICIAL Defects in timber INSECT ATTACK. Insects attack woods by boring on its surface. These holes render wood unsuitable for project.

ARTIFICIAL Defects in timber For further reading: https://civiltoday.com/civil-engineering-materials/timber/85-defects-in-timber-types-and-reasons