The use of more wood materials is required recently from the environmental point of view in Japan. In case of the use of wood materials for port facilities, the main deterioration factors are marine borers (limnoria, teredo, etc.) for submerged members and physical factors (climatic action, etc.) for non-submerged members. In this study, the seasonal change of the marine borer attack, the effects of wood species and the effects on the strengths were investigated by immersion tests in the real seawater, and the effects of wood species on the weathering deterioration were examined by the exposure tests in coastal atmosphere. Both the tests were carried out at Yokosuka in front of Tokyo Bay.
　As the results of the immersion tests, the degradation rate by limnoria largely depended on the hardness of wood, while the degradation rate by teredo did not depend on the hardness of wood and that was small for the species such as Icho (Ginkgo biloba), Sawara (Chamaecyparis pisifera), Koyamaki (Sciadopitys verticillata) and Kusu (Cinnamomum camphora). The compressive, bending and tensile strengths of Sugi (Cryptomeria japonica) specimens deteriorated by marine borers were lower than the values expected from the weight loss ratios. As the results of the exposure tests in a coastal atmosphere with additional spray of seawater, the dimensional losses (i.e. physical deterioration) of broadleaf woods were larger than those of coniferous woods contrary to popular belief.