Timber Defects
Knots
A hard cross grain mass of
wood that is formed in the
trunk of a tree where a branch
grows.
Knots spoil the appearance
and reduce the strength
properties of wood. It also
raises the seasoning defects
and makes difficulties during
wood working.
Gum Pockets
Cracks in the timber which contain gum.
Shakes
• A Shake is a partial or complete separation
between the adjoining layers.
• Maybe caused by growing stresses in the tree
or by the impact of the tree with the ground
during felling
Cup Sahkes
• Separation of wood fibres around the growth
rings
Heart Shake
• A split which extends from the pith
Felling Shake
• Are fractures across the grain in which the fibres are broken
transversely or are crushed by compression.
• Various causes are suggested, such as felling across
obstructions, and failure inside the growing tree caused by
high winds.
Cupping
• A concave curvature across the face of a board.
• Curvature is usually away from the centre of the tree.
Spring
• Curvature along the edge of the board.
Bow
• Curvature along the wide face of the board in
the direction of the length.
Twist
• A spiral distortion along the length of a board.
• Also known as wind.
Wane
• Edges or corners of sections of timber that
encroach into the area of the bark.
Splits & Checks
• A split is a longitudinal crack which extends
through the board, usually on the end
• A check is a longitudinal crack that does not
extend all the way through the board.