Abstract: A method of testing a wooden structural member provides a quantitive estimate of the residual strength of the member. The method includes determining the presence of anomalies in each of a plurality of intersecting transverse paths through the structural member at a tested cross section of the structural member. A unit cross section of corresponding shape to the tested cross section has a plurality of predefined regions. For each region of the plurality of regions a determination is made that the region is suspect if each of the paths intersecting at the region has indicated an anomaly. A residual stiffness property for the cross section is calculated discounting at least some of the suspect regions. The calculated residual stiffness property may be displayed together with a visual representation of the cross section of the wooden structural member with the suspect regions highlighted.