Long-term performance of DMDHEU-treated wood installed in different test set-ups in ground, above ground and in the marine environment

The field performance of wood modified with 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) is reported after outdoor exposure above ground (UC3), in ground (UC4) and in the marine environment (UC5) at six different sites in Europe and Australia. Results from more than seven years field testing with respect to the DMDHEU treatment level, wood species (Scots pine, European beech, spotted gum and slash pine) and climate conditions were evaluated. DMDHEU was shown to significantly improve the biological durability of Scots pine sapwood after exposure under UC3, UC4 and UC5 conditions, which confirmed previous findings on the laboratory scale. The latter was classified as 'durable to very durable' (durability class DC1-2). However, DMDHEU modification seemed to be more efficient in Scots pine, slash pine and spotted gum so that higher chemical loadings are required for European beech to reach similar resistance against wood-destroying fungi. Under feeding pressure of Teredo navalis, DMDHEU treatment was graded as 'durable'.