Drawing No. EH–MT–026 // Engineering Materials
Wood Properties
Reviewed August 2026
Coast Douglas-fir clear wood at approximately 12% moisture content is used only as an orientation point. Wood is orthotropic and hygroscopic, so properties depend on species, density, moisture content, grain direction and natural defects.
Representative properties
Switch units without changing the underlying material reference.
What changes these properties?
Engineering variability
- Modulus and strength depend on grain direction; longitudinal stiffness greatly exceeds transverse stiffness.
- Moisture content has a major effect below fiber saturation and also drives dimensional change.
- Knots, slope of grain, checks and grading reduce structural-lumber properties relative to clear-wood values.
- Thermal conductivity and heat capacity vary with density, moisture and direction.
Selection note
For structural timber use grade-specific design values from the governing timber code/standard. Clear-wood handbook values are educational/reference data, not allowable stresses.
Do not combine strength from one grade/condition with modulus, thermal data or temperature limits from another without checking compatibility. Where the overview shows a range, it is intended to expose variability—not establish allowable bounds.
Property interpretation
Stiffness vs strength
Young’s modulus controls elastic deformation. Yield or fracture strength controls how far the material can be stressed. These are separate material characteristics.
Thermal response
Thermal conductivity controls temperature gradients, specific heat contributes to thermal inertia, and expansion controls thermally induced strain when movement is restrained.
Temperature transition
The final property card is deliberately labeled “melting / transition.” Metals often have a solidus–liquidus range; amorphous polymers and glass use softening or glass-transition concepts; concrete and wood decompose instead of exhibiting one clean melt point.
Technical sources
Source hierarchy favors manufacturers, industry associations, standards bodies and government engineering references. Strength data must still be reconciled with the exact procurement specification.