Abstract
To evaluate the natural decay durability of valuable domestic softwoods which are used for preservative treatment in our country, we carried out decay test by European standard method. Of all test wood species, Japanese larch (Larix leptolepis) showed slightly high natural decay durability compared to other 4 wood species, Japanese red pine (Pinus densiflora), pitch pine (Pinus rigida), Japanese cedar (Cryptomeria japonica), and scots pine (Pinus sylvestris). However, all of evaluated domestic softwood species in this study caused high weight losses over about 30% in heartwood by test fungus, Poria placenta. We can hardly expect a good natural decay durability from these softwood species. According to the classification of the natural durability of European standard (EN 350-1), they are classified into "Not durable" or "Slightly durable". Therefore, if using these softwoods as exterior materials, we must do preservative treatment to ensure durability.
