Predicting the decay resistance of timber above-ground: 1. Climate effects

IRG/WP 06-20330

L P Francis, J Norton

Despite the benefits of using timber as a building product, it is disadvantaged by current Australian Standard durability classifications which lack the sensitivity desired by engineers and architects. To address the need for more sensitive timber service-life information in Australia, an above-ground durability research program was established in 1987. One focus of research is the relationship between climate variables and the durability of timber used above-ground in weather-exposed applications, and an update of analyses are presented in this paper. Through its effect on biodeteriogens, climate has long been accepted to have a strong influence on timber durability. To begin to quantify this relationship, current deterioration results from L-joints installed above-ground throughout Eastern Australia were analysed for correlation with selected climate measures. When data from all ten field sites were included in analyses, the relationship between timber decay and average vapour pressure deficit (AVPD) was statistically significant for seven of the nine species tested; the two most durable species had not deteriorated sufficiently to provide reliable data for analysis. In general AVPD was most strongly correlated with L-joint deterioration; followed by Carter and Cause’s DPI climate index, percent wet days, average evaporation, Scheffer’s climate index and then average maximum temperature. Direct relationships between durability and climate measures were considerably weaker when the results from the Mt Isa site were excluded from analyses. Mt Isa is an exceptionally dry and hot location.

Keywords: above-ground durability, climate, L-Joint, biodeterioration modelling

Conference: 06-06-18/22 Tromsoe, Norway

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