Stress grades table
Use the strength groups table to determine if a timber could meet specified stress grades.
Strength groups: S1 and SD1 are the strongest strength groups for unseasoned and seasoned timber respectively.
Stress grades: Higher F ratings are given to stronger boards.
Structural grades: Structural 1 can achieve the highest stress grade.
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Stress grades & visual grades in relation to strength group for seasoned (SD) and unseasoned (S) timber* |
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1. Seasoned timber |
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|
Strength group |
SD1 |
SD2 |
SD3 |
SD4 |
SD5 |
SD6 |
SD7 |
SD8 |
|
|
high |
→ |
→ |
→ |
→ |
→ |
→ |
low |
|
Visual grades |
Stress grades |
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|
Structural 1 |
F34 |
F34 |
F27 |
F22 |
F17 |
F14 |
F11 |
F8 |
|
Structural 2 |
F34 |
F27 |
F22 |
F17 |
F14 |
F11 |
F8 |
F7 |
|
Structural 3 |
F27 |
F22 |
F17 |
F14 |
F11 |
F8 |
F7 |
F5 |
|
Structural 4 |
F22 |
F17 |
F14 |
F11 |
F8 |
F7 |
F5 |
F4 |
|
Softwoods only - |
— |
— |
— |
— |
F7 |
F5 |
F4 |
— |
|
|
|
|
|
|
|
|
|
|
2. Unseasoned timber |
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|
Strength group |
S1 |
S2 |
S3 |
S4 |
S5 |
S6 |
S7 |
SD8 |
|
|
high |
→ |
→ |
→ |
→ |
→ |
→ |
low |
|
Visual grades |
Stress grades |
|||||||
|
Structural 1 |
F27 |
F22 |
F17 |
F14 |
F11 |
F8 |
F7 |
— |
|
Structural 2 |
F22 |
F17 |
F14 |
F11 |
F8 |
F7 |
F5 |
— |
|
Structural 3 |
F17 |
F14 |
F11 |
F8 |
F7 |
F5 |
F4 |
— |
|
Structural 4 |
F14 |
F11 |
F8 |
F7 |
F5 |
F4 |
— |
— |
|
Softwoods only - |
— |
— |
F7 |
F5 |
F4 |
— |
— |
— |
Source: AS 2878-2000 Timber—classification into strength groups (Standards Australia 2000).
* This table does not apply to white cypress (Callitris glaucophylla), which has equivalent strength properties in seasoned and unseasoned conditions, with available stress grades: F7, F5 and F4.
** The visual grade ‘Structural 5’ only applies to softwoods (e.g. Pinus, Picea, Larix, Araucaria and Abies species).