Conventional pressure treatment of many Australian hardwoods results in little to no penetration of heartwood and a non-uniform envelope treatment of <5 mm surrounding a mostly untreated core. This is a major issue for many of the low durability plantation hardwood timbers that are grown in Tasmania, which contain high percentages of heartwood. Long term studies on softwoods such as spruce decking suggest that shallow barrier treatments can provide decades of protection; however, it is unclear whether shallow heartwood treatments would perform as well on lower durability hardwoods. Field tests would take decades to produce meaningful results, although accelerated laboratory decay tests might help bridge the testing gap. This study evaluated a laboratory method to determine the minimum effective level of chromated copper arsenate (CCA) penetration into Eucalyptus nitens heartwood that prevented fungal colonization by the brown rot Fomitopsis ostreiformis. Visual and culturing results indicated that the epoxy barriers failed to prevent fungal colonization on the untreated surfaces and further studies are underway to identify more suitable barriers for assessing preservative penetration.

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