Abstract
A timber handrail made from the hardwood Keruing (Dipterocarpus spp.) and exposed in European Hazard Class 3 on railings at the Southbank, London was investigated to (i) determine the visual damage on the hardwood railing cappings quantitatively and to (ii) identify the causal organisms, and (in) to characterise their decay patterns in the wood. The service life of this handrail of at least 25 years so far shows impressively that Keruing of this quality has exhibited a reasonable resistance to decay for the period. However, the selection of this timber for the construction may not have been ideal due to its large dimensional movement and the effect of this on the aesthetic appearance, in the form of extensive surface cracking, of several of the timber sections, including those rated as free from decay. The two principal decay organisms were identified as the white rot fungus Phellinus contiguus (Fr.) Pat. and the brown rot fungus Dacrymyces stillatus Nees:Fr. Decay patterns observed in the samples of the handrail and in invitro tests demonstrated the ability of P. contiguus and D. stillatus to cause a soft rot -like decay pattern in addition to their typical modes of action, i.e. white and brown rot. These results indicate that "classical" criteria in linking decay features to certain decay types and fungi can be much more complex than expected. Depending on the fungal species, a transition or switch mechanism between brown + soft rot and white + soft rot respectively is probable.