In broad terms the degradation of structural timbers result from attack by one or more of the following wood destroying agents: Chemical delignification; fungal decay; wood borers; and termites.
Failure of timber from such attack is frequently associated with lack of maintenance; and contributing to this, a general lack of knowledge of the characteristics and properties of the material itself.
The symptoms and causes outlined in the following examples. Are not intended to be all inclusive. However they will give an indication of the more common characteristics which may be readily observed at the time of inspection.
Roof, wall and floor structure
Chemical delignification is the breakdown of lignin (the natural glue that binds the wood cells together) through chemical action. Signs of damage to structural timber include:
The surface of the wood becomes hairy; loss of strength resulting in deformation; and collapse.
Fungal decay is the microbiological degradation of timber caused by soft rot fungi and decay fungi.
Signs of damage to structural timbers include;
Split in timber which are sometimes longitudinal but more usually cuboidal in shape;
Timber which has reduced both in moisture content and size as indicated by cracking either along or across the grain or by fibres coming apart in stringy manner’
Misshapen timbers, e.g. cupping and ridging of floorboards;
Loss of strength resulting in deformation; and collapse.
Wood Borers and Termites
Wood borers are wood destroying insects belonging to the order “Coleoptera” which commonly attack timber. Signs of damage to structural timbers include:
Adult beetles flight (exit) holes;
Abnormal depressions in the surface of timber, the gain may stand out and the surface of the timber be drawn in, and in other cases the timber may bulge out slightly
Loss of strength resulting in deformation; and collapse (only rarely)