Modulus of elasticity (MOE)
Modulus of elasticity (MOE) is a material's stiffness, in MPa or GPa. For pine framing, the MGP number IS a rounded MOE in GPa. Distinct from bending strength.
Ask Chalkline about this →The modulus of elasticity (MOE) is a measure of how stiff a material is: the ratio of stress (load per unit area) to strain (the resulting deformation) within the elastic range. It is expressed in megapascals (MPa) or gigapascals (GPa) (1 GPa = 1,000 MPa). For a structural member, higher MOE means stiffer: less deflection under the same load.
Why it matters for timber framing
For radiata pine framing in Australia, MOE is literally what machine grading measures. Machine-graded plantation softwood is bent in a mill, the deflection response is recorded, and the stick is stamped with an MGP grade (verified 2026-05-28, see pine framing grades):
| MGP grade | Characteristic MOE | F-grade equivalent |
|---|---|---|
| MGP10 | 10,000 MPa (10 GPa) | F5 |
| MGP12 | 12,000 MPa (12 GPa) | F8 |
| MGP15 | 15,000 MPa (15 GPa) | (no direct F-grade equivalent) |
So the MGP number IS the rounded MOE in GPa: MGP10 is 10 GPa, MGP12 is 12 GPa. That is the whole logic of the naming.
MOE vs bending strength
MOE and bending strength are two different properties, and the timber world has separate grading systems for each:
- MOE (stiffness): how much a member deflects under load. Drives the MGP grades (machine-graded pine) and the deflection columns of an AS 1684 span table.
- Bending strength: how much load a member can take before it ruptures. Drives the F-grades (F5, F7, F8, F11, F14) and the strength columns of an AS 1684 span table.
A floor joist span limited by deflection (sagging) is controlled by MOE. A lintel span limited by bending failure is controlled by bending strength. The AS 1684 span tables account for both: the published maximum span is the lower of the deflection-limited and strength-limited result.
What a builder does with MOE
You rarely calculate MOE on site. What it means in practice:
- Pick the right MGP grade for the span. Long-spanning floor joists usually need MGP12 (12 GPa) rather than MGP10 (10 GPa) to keep deflection inside the L/300 limit AS 1684 applies. The span table picks for you; the MOE is the reason.
- Check the stamp. The MGP stamp on the stick is the proof of grade. If the bundle is unstamped or the grade is below what the span table assumes, the frame is non-compliant.
- Engineered members carry separately quoted MOE. LVL beams, I-joists, and glulam each have their own MOE values, typically higher than sawn pine, which is what makes the longer spans possible.
Also known as: MOE, Young’s modulus, stiffness modulus, E-value.
Category: Structure / timber
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Last updated: 2026-05-28. Verified: 2026-05-28. Quarterly review for currency.