Natural durability of Norwegian wood species for above ground applications – Project presentation and preliminary results
P O Flæte, G Alfredsen, F G Evans
In Norway exterior wood structures have traditionally nearly exclusively been made of treated and untreated Norway spruce (Picea abies (L.) Karst) and Scots pine (Pinus sylvestris L.). In recent years there has been a tendency that other tree species, like various domestic hardwoods and imported species have been used in exterior above ground applications, often unfinished. For several wood species, especially hardwoods, information regarding the durability in use class 3 is lacking. The test procedures prescribed in the European standards, both laboratory and field tests, have some weaknesses regarding to natural durability testing. Hence, some new methods for accelerated above ground testing have been put forward. The main objectives of this project are to evaluate natural durability of Norwegian wood species for above ground applications, and to study various methods for assessing decay in wood. This paper presents the material and methods used in the project, and report the results from double layer tests after one year of exposure. No decay was detected, but almost all wood species were considerably discoloured. Thuja (Norw.), Thuja (Am.), Intsia and Tectona had the least amount of discolouration. The Norwegian softwood species had generally less discolouration than the Norwegian hardwood species. CCA and Cu preservative impregnated and FA modified Pinus sylvestris sapwood had more cracks than most of the untreated wood species. Moreover, some of the Picea abies qualities and Pinus sylvestris sapwood samples had substantial amounts of cracks.