Non-destructive testing methods available for wood and their applicability in the Philippine setting

The lumber stress grading system in the Philippines is now in the final stages of development. Such system will pave the way for more efficient utilization of timber. It will have a significant impact not only in the reduction of the cost of timber structures but also in the forest conservation efforts of the government. The strength of the wood at the time of grading will not necessarily remain the same in service. It could change depending on a number of factors which include moisture content and the occurrence of decay. It is therefore necessary that timber, especially the load-bearing ones forming part of structures, be monitored as to their soundness in order to maintain their structural integrity. There are a number of non-destructive testing (NDT) methods which are applicable in wood. Some are already in use while the others are still in the development stage. These include stress grading, stress waves and vibration methods, physical methods, and scanning technologies. Some of the NDT methods are applicable in the Philippines considering the stage of the country's stress grading system development, costs, and availability of equipment and trained personnel. These include stress grading, proof grading, low frequency stress waves, ultrasonics, vibration methods, resistance drilling, and Pilodyn. However, these methods should first be pilot tested before their full-scale use. The NDT methods are necessary to complement the lumber stress grading system. They can be used as service technologies for machine graded lumber (MGL) users in order to ensure the continuous satisfactory service of MGL. While the above mentioned NDT methods can now be employed in their present technological stage, there is still a need to conduct research activities to improve their accuracy and cost-effectiveness when used in wood