Stress grade
A stress grade is a structural classification for timber indicating its bending, tension, and stiffness capacity. Used to read AS 1684 span tables correctly.
Ask Chalkline about this →A stress grade is a structural classification assigned to a piece of timber that indicates its capacity to resist bending, tension, compression, and shear forces. In residential framing, stress grades are the primary input to AS 1684 span tables: the tables tell you what size member to use for a given span and load, but only for a specific stress grade of timber.
The common stress grades for pine framing in Australia are MGP10, MGP12, and MGP15 (Machine Graded Pine, where the number is an approximate stiffness value in GPa). Hardwood framing uses F-grades (F5, F8, F14, F17, F27). LVL and engineered products have manufacturer-certified grades that are not directly interchangeable with AS 1684 span tables.
Stress grade is established either by machine grading (most pine from a large mill) or visual grading. The supplier’s delivery docket or the grade stamp on the timber should confirm the grade. If the grade cannot be confirmed, the timber cannot be safely entered into an AS 1684 span table.
Also known as: Structural grade, timber grade.
Category: Structural / Framing.
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Last updated: 2026-05-08. Verified: 2026-05-08.