Wood is a traditional building material in the marine environment, where it is exposed to extremely harsh conditions. Most of the indigenous softwood and hardwood species in Europe are not durable against attack by marine organisms. Recently, wood modification has been considered as an alternative to protect non-durable wood species under use class (UC) 5 (EN 335, 2013) conditions. The present study focused on treatment of solid wood and laminated veneer lumber (LVL) with the thermosetting resin 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU), its derivatives and low molecular phenol-formaldehyde (PF). The results evidenced that treatments with formaldehyde-containing thermosetting resins like DMDHEU and PF improved the resistance against attack by shipworms significantly. The latter was shown for both, solid wood and LVL specimens. In Scots pine sapwood specimens, treatment with DMDHEU caused higher improvements in the resistance against shipworm attack compared to Radiata pine and poplar specimens. Formaldehyde-free DMDHEU derivatives did not provide any resistance against marine borers compared to untreated control panels. In summary, wood modification with thermosetting resins has good potential to be used in the marine environment (UC 5). However, the mechanisms of protective action are not fully understood yet and require further studies on how curing processes, chemical distribution and production processes for wood-based composites affect the marine borer resistance. Besides that, an upscaling to large-sized dimensions is essential to implement such innovative technologies as building materials under UC 5 conditions in the near future.

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