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Everyone has heard of wood preservers but what are they, why are they so important and how do they work?

Although wood is an amazingly versatile and durable material, it can be susceptible to deterioration especially where mold, algae, fungi and wood-boring insects are likely. The best way to protect and preserve wood, including timbers that have been pressure-treated is to use a wood preservative.

In past years, treatments such as creosote and engine oil were used to preserve exterior timber, however, as a greater understanding of the toxic nature of these products became known many were banned or restricted for commercial use only by strict government legislation. Thankfully, todays domestic wood preservers are safer for both the user and environment.

Types of wood preservative

Most wood preservatives nowadays are manufactured with similar ingredients due to the government led restrictions, however the formulas and the strength of those ingredients do vary. In layman terms:

  • Clear preservers help retain the natural appearance of the wood

  • Coloured preservatives act as a dual purpose treatment and stain that change the colour of the timber

  • Solvent-based formulas have been around longer and are known for their penetrative properties

  • Water-based treatments confirm to strict V.O.C (Volatile Organic Compounds) regulations being imposed by UK, European and Worldwide governments, making them safer for the environment

How do wood preservers work?

The key ingredients of wood preservers are biocides and insecticides with the most commonly used being Permethrin. Permethrin is an insecticide in the pyrethroid family. Pyrethroids are synthetic chemicals that act like natural extracts from the chrysanthemum flower. Other common ingredients include Iodo propynyl Butylcarbamate and Tebuconazole. Most modern wood preservers are safe for humans, animals and plants when dry, meaning that they can be used on sheds, fences, wooden trellis, dog kennels, stables, joinery and more.

Are wood preservers an all-in-one solution?

Although wood preservers are great at protecting wood from biological threats, they only offer limited weather protection and direct contact durability. Some wood preservers contain a small amount of wax which means that rainwater will initially bead and run off treated wood. Surfaces treated with just a wood preservative however, will likely need re-coating every couple of years. Ideally, wood that has been treated with a preserver should also be treated with a suitable top coat such as an wood oil, wood paint, wood varnish. These top-coat products seal in the preserver and provide protection against weathering and wear from direct contact.

If overcoating a wood preservative with a water-based paint or varnish, it’s important to select a preserver that does not contain wax.

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