All measures that are taken to ensure a long life of wood fall under the definition wood preservation (timber treatment). Apart from structural wood preservation measures, there are a number of different (chemical) preservatives and processes (also known as timber treatment or lumber treatment) that can extend the life of wood, timber, wood structures or engineered wood. These generally increase the durability and resistance from being destroyed by insects or fungus.

Timber or lumber that is treated with a preservative generally have it applied through vacuum and/or pressure treatment. The preservatives used to pressure-treat timber are classified as pesticides. Treating timber provides long-term resistance to organisms that cause deterioration. If it is applied correctly, it extends the productive life of timber by five to ten times. If left untreated, wood that is exposed to moisture or soil for sustained periods of time will become weakened by various types of fungi, bacteria or insects.

Chemical preservatives can be classified into three broad categories: Water-borne salts, Oil-borne preservatives, and Light Organic Solvent Preservatives (LOSPs).

Probably the first attempts made to protect wood from decay and insect attack consisted of brushing or rubbing preservatives onto the surfaces of the treated wood. Through trial and error the most effective preservatives and application processes where slowly determined. In the Industrial Revolution, demands for such things as telegraph poles and railroad ties helped to fuel an explosion of new techniques that emerged in the early 19th century. The sharpest rise in inventions took place between 1830 and 1840, when Bethell, Boucherie, Burnett and Kyan were making wood-preserving history. Since then, numerous processes have been introduced or existing processes improved. The goal of modern day wood preservation is to ensure a deep, uniform penetration with reasonable cost, without endangering the environment. The most widespread application processes today are those using artificial pressure through which many woods are being effectively treated, but several species (such as Spruce, Douglas Fir, Larch, Hemlock and Fir) are very resistant to impregnation. With the use of incising, the treatment of these woods has been somewhat successful but with a higher cost and not always satisfactory results. One can divide the wood-preserving methods roughly into either non-pressure processes or pressure processes.

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