For structural timber, certain key properties need to be assessed in order to ensure building safety, and economic use of the material. The means by which this is achieved is known as “strength grading”, and sometimes by the old terminology “stress grading”.  There are two parallel systems for grading: visual and machine, both of which follow the same fundamental basis: timber is sorted into grades according to a non-destructive assessment that is predictive of the grade determining properties. The collective characteristic properties of the timber sorted into those grades determines the strength class. A strength class is simply a grade with associated numbers for strength, stiffness and density that can be used in design.  Read the full summary by Dan Ridley-Ellis here.

Dan is currently part of, Wood Properties for Ireland (WoodProps) a joint project between the Timber Engineering Research Group at NUI Galway and the Centre for Wood Science and Technology, Edinburgh Napier University. The project is focused on addressing issues related to characterisation of Irish-grown timber and associated work at National and European level in standardisation for structural timber quality and production – with a particular focus on grading.

 

A summary of timber strength grading