At present the majority of structural timber consists almost entirely of softwoods, mainly spruce (Picea abies). Accordingly, the grading machines used in Europe to date are approved for softwoods only, so far the new multi-sensing grading machines employed in Germany, Austria and Sweden have only been approved for the grading of spruce timber. With regard to an extended application of machine grading and a better use of available timber, possibilities of machine grading were investigated using more than 2000 joists and planks of the following species:

• Picea abies
• Pinus sylvestris
• Larix decidua
• Pinus sylvestris
• Quercus robur / Quercus petraea
• Fagus sylvatica

The following non-destructive methods were evaluated:

• bending methods
• vibration methods
• ultrasonic methods
• radiation methods

Moreover, various combinations of these grading methods were also investigated. For comparison, all specimens were graded visually according to DIN 4074 to determine their characteristic bending and tensile strength and stiffness properties.

Results show that machine grading is suitable for the grading of all the above listed species. Compared to visual grading, they allow structural sawn timber to be upgraded to higher strength classes. This could improve the chances for timber to be used in construction.
The performance of the vibration and ultrasonic grading methods can be improved by including density measurements. Moreover, determination of knot ratio, e.g. by scanning or radiation, improves accuracy for all the grading methods listed above.