Is laboratory testing of decay resistance questionable as a single criterion for natural durability?
J Van Acker, M Stevens, T Van Cauwenberghe, T Seynaeve
In a laboratory test set up over 20 hardwood species were evaluated according to the European Standard EN 350-1 including Basidiomycete and soft rot testing. Half of the species used were of a known natural durability. The Basidiomycete testing was carried out using Coriolus versicolor, Gloeophyllum trabeum and Coniophora puteana in a malt agar test similar to EN 113. From this test it was not possible to rank the wood species according to known natural durability, only a distinct differentiation between species belonging to the group of durability classes 1 to 3 and the ones of durability classes 4 and 5 was noted. Since most wood species with little information on durability are so-called lesser known species belonging to the tropical hardwoods, it seems that only limited additional information is gained from brown rot tests supplementary to white rot tests. Both types of laboratory soft rot tests according to ENV 807 (vermiculite and soil) are able only to identify significantly the durability classes 1 to 4 from class 5, although somewhat better indications are obtained from the soil test. It is evident that other types of fungal attack like blue-stain in service, being an important parameter for window joinery, is not correlated at all with natural durability data obtained from soil testing. It is concluded from this research that durability testing would be better hazard class oriented in order to identify functionality of the end products derived.