Stress grade

The classification of a piece of timber to indicate its characteristic structural properties and stiffness. It is related to timber strength groups.

The classification of a piece of timber (for structural purposes) to the relevant Australian Standard, to indicate its characteristic structural properties and stiffness. It is related to timber strength groups. Structural timber is generally sold as a (stress) graded product. A stress grade is the classification of a timber for structural used in structural applications and described in AS1720 SAA-Timber Structures Code.

Stress grades are derived from either visual- or machine-grading, which specify the stress limits that apply to timbers used for structural applications. Stress grades are known by ‘F’ grades (F4 to F34); F14 indicates that the basic working stress for that timber is around 14 MPa. Timber to be used in a specific structural application must meet the required stress grade specified by the architect or designer.

See the guide: Strength groups & stress grades.


Below are a list of values users can choose for this field group.

  • F11 - The stress grade classification of a piece of timber for structural purposes (to the relevant Australian Standard) to indicate its characteristic structural properties and stiffness.
  • F14 - The stress grade classification of a piece of timber for structural purposes (to the relevant Australian Standard) to indicate its characteristic structural properties and stiffness.
  • F17 - The stress grade classification of a piece of timber for structural purposes (to the relevant Australian Standard) to indicate its characteristic structural properties and stiffness.
  • F22 - The stress grade classification of a piece of timber for structural purposes (to the relevant Australian Standard) to indicate its characteristic structural properties and stiffness.
  • F27 - The stress grade classification of a piece of timber for structural purposes (to the relevant Australian Standard) to indicate its characteristic structural properties and stiffness.
  • F34 - The stress grade classification of a piece of timber for structural purposes (to the relevant Australian Standard) to indicate its characteristic structural properties and stiffness.
  • F4 - A stress grade classification of softwood timber for structural purposes. F4 applies only to softwoods (Pinus, Picea, Larix, Araucaria and Abies species).
  • F5 - A stress grade classification of softwood timber for structural purposes. F5 applies only to softwoods (Pinus, Picea, Larix, Araucaria and Abies species).
  • F7 - A stress grade classification of softwood timber for structural purposes. F7 applies only to softwoods (Pinus, Picea, Larix, Araucaria and Abies species).
  • F8 - A stress grade classification of softwood timber for structural purposes. F8 pplies only to softwoods (Pinus, Picea, Larix, Araucaria and Abies species).
  • Stress grade-non-structural - non-structural