In carpentry and construction, solid lumber changes dimensionally as it absorbs or releases moisture below its fiber saturation point. Match each lumber moisture and shrinkage term with its correct defining characteristic.
- Tangential shrinkageDimensional movement along the growth rings, exhibiting the highest rate of shrinkage (roughly 6% to 10%).
- Radial shrinkageDimensional movement perpendicular to growth rings from pith to bark, exhibiting moderate shrinkage (roughly 3% to 5%).
- Longitudinal shrinkageDimensional movement along the length of the board, exhibiting negligible shrinkage (typically 0.1% to 0.2%).
- Fiber saturation pointThe stage (around 28% to 30% moisture content) where cell cavities are empty of free water but cell walls remain fully saturated.
Answer
Tangential shrinkage matches dimensional movement along the growth rings (highest rate); Radial shrinkage matches dimensional movement perpendicular to growth rings (moderate rate); Longitudinal shrinkage matches dimensional movement along the board length (negligible rate); Fiber saturation point matches the stage where cell cavities are empty but cell walls are saturated.
Wood is an anisotropic material that shrinks and swells at different rates depending on the direction of grain orientation relative to annual growth rings. Tangential shrinkage (parallel to the rings) is the greatest, radial shrinkage (perpendicular to the rings) is moderate, and longitudinal shrinkage (along the length) is negligible. Shrinkage only begins once wood dries below the fiber saturation point, where bound water leaves the cell walls.
Step-by-Step Solution
Key Concept
Lumber moisture behavior, fiber saturation point, and directional shrinkage rates across grain orientations
Estimated Time:1m 0s