Modulus of Elasticity of Timber
Timber stiffness comes with a species, a grade and a direction attached: parallel to grain it competes with concrete, across the grain it barely counts.
| SPF No.1 and No.2 | about 9.5 GPa |
| Douglas Fir Larch No.1 and No.2 | about 11 to 12.5 GPa by code and grade |
| MSR lumber 1650f 1.5E | 10.3 GPa, printed right in the name |
| MSR lumber 2100f 1.8E | 12.4 GPa |
| LVL, typical | 13 to 14 GPa |
| EN strength class C16 | Emean 8.0 GPa |
| EN strength class C24 | Emean 11.0 GPa |
| Perpendicular to grain | a small fraction, guidance values only |
Notes for design and site
Machine stress rated lumber gives the game away in its label: 2100f 1.8E means 1.8 million psi, which is 12.4 GPa, measured on every piece as it leaves the mill. Visual grades carry tabulated averages instead, which is why the same nominal species spans a range depending on which code table you are reading. When stiffness governs, MSR and engineered products earn their premium.
Two multipliers matter more than the third decimal of E. Duration: permanent loads roughly double deflection through creep, and both CSA O86 and the NDS carry explicit factors for it. And moisture: wet service knocks stiffness down as well as strength. Design to the code value for your exact species, grade and condition rather than a generic softwood number.
Related Calculators and Reference
- Joist Span Calculator: where timber E decides the answer.
- Timber Class C24: the workhorse EN class with its full property set.
- Beam Deflection Studio: run a timber beam through the classic cases.
- Modulus of Elasticity of Steel: the constant cousin for comparison.
- Canadian Wood Council: design resources for wood construction in Canada.