The use of wood for demanding construction applications is increasing in Europe. Wooden constructions are frequently designed of susceptible conifer wood, which is endangered by wood decay fungi in wet applications. Therefore in many cases treating wood with preservatives is unavoidable to ensure the desired service life. However, chemical treatment of wood can result in changes of its mechanical properties. There are contradictory results published in literature regarding the influence of the various impregnation agents on relevant mechanical properties. In order to elucidate mechanical properties of impregnated wood, Scots pine (Pinus sylvestris) sapwood and Norway spruce (Picea abies) wood were impregnated with a copper-ethanolamine based system, an aqueous solution of boric acid and a solvent based wood preservative. For comparison, wood samples were impregnated with deionised water. After conditioning, half of the samples were artificially aged according to the EN 84 leaching procedure. Afterwards, samples were oven dried, and their bending and compressive strength in axial and radial direction was determined. In parallel, structural integrity of the samples was determined in High-Energy Multiple Impact (HEMI) tests. The results clearly showed that treatment with wood preservatives does not have significant influence on the mechanical properties, with exception of non-aged copper-ethanolamine and boric acid treated wood that exhibited significantly lower structural integrity of wood. The negative effect on strength and structural integrity was found to be reversible through exposure to liquid water or high relative humidity.

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