Wood is a material that is widely used in many applications but it has some weak properties which can be modified with various solutions. The aim of this study is to examine how preservatives affect wood properties. The effects of preservatives are classified into five categories: mechanical properties, weathering, moisture resistance, biological durability and fire resistance. The different properties have been studied at varying intensity in wood science – for example moisture resistance and biological durability have been studied quite a lot, while weathering is a rather new issue. Preservatives have a minor effect on wood, depending on the solution, treatment, and wood species, but generally preservatives cannot cause dramatic changes to the properties of wood, whereas the moisture content has a great effect on the characteristic of wood. In addition to the properties of wood and the weight percentage gained after modification, the crucial properties of modifiers are for example the pH value and the comparison between water- and oil-based solutions.

Key words: wood, modification, property, preservative