Which is better: Wood Impregnation Varnish or Preservative (Exterior Use) The right product for your wood can make a big difference in the longevity of the wood, whether it's wooden windows, doors or a wooden deck. It can also make a significant difference to future maintenance, and a wrong or inferior product used as a short-term saver can end up costing much more in the long run.

There are two main products for external use with many different sub-products under them. However, the most basic is either wood impregnation varnish which tends to form a coating over the wood, or a preservative, which penetrates and nourishes the wood and basically sits within the wood.

Varnishes often form a hard protective coating that cannot contract and expand with temperature fluctuations and often cracks or peels, making maintenance more difficult and expensive. Preservatives (usually oil based) penetrate the wood and although they do not usually form a hard protective coating, they nourish the wood and are often much easier and more cost effective to maintain than with varnish.

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