Damp and Timber Specialists for 50 years

Timber’s potential as a building material is almost unmatched: not only is it strong, long-lasting, and beautiful to look at, but it’s an excellent natural insulator. It helps you cut down on your energy bills by absorbing heat from the air, keeping your home cosy even in winter. However, timber does require some additional preservation. This is to protect it from damage and extend its lifespan.

The team at Prokil has over 50 years’ experience treating and preserving all types of timber. In this guide, we discuss why timber needs to be preserved, how it’s done, and what to do if your timber requires preservation treatment.

Why Is Timber Preservation Necessary?

As a natural material, timber is vulnerable to a number of threats. These include:

Preservation helps prevent timber from being affected by the issues listed above, ensuring it stays strong and free from disease for many years.

What Is Used To Preserve Timber?

The specific type of preservation treatment used on timber depends on several factors, including budget, the type of wood, and whether treatment is to be carried out in the processing facility or in-situ.

Wood Stains and Paints

Lightweight and microporous, wood stains are solvent or water-based stains that are brushed onto timber. Colour pigments can be added to the stain to help freshen up the appearance of the timber.


ASCU is a special powder that is dissolved in water to produce a preservative solution. The ratio of ASCU to water should be 6 to 100. The solution is applied to timber by spraying.

Coal Tar

Once melted, hot tar is coated onto the timber using a brush. Although tar is fire-resistant and very cheap to buy, it has a strong odour and cannot be painted on.

Creosote Oil

Tar can be distilled to create creosote oil. Applying creosote oil requires a special method: seasoned and dried timber is placed inside an airtight chamber. Air is sucked out and oil is pumped in at 50°C. The timber is removed after around two hours, which is how long it takes to absorb the oil. Creosote oil is hardy but strong smelling and flammable, so it is usually used on timber that is to be kept outside.

Chemical Salts

Chemical salts like zinc chloride, mercury chloride, and copper sulphate can be dissolved in water to create a preservative solution. They are fireproof and odourless, and are usually applied with a spray gun.

Rod Insertion

Boron rods can be inserted into particularly durable timber to strengthen it. This method is typically only used on timber that is integral to a building’s structure and cannot be replaced.

What To Do If Your Timber Needs Preservation Treatment

Although preservation is usually carried out during the processing process, sometimes timber needs to be treated when already in-situ. This could be because the original preservation has worn away, or if the timber was not properly preserved to begin with. Timbers that require this treatment are typically bedded and impossible to replace.

At Prokil, we offer two forms of in-situ timber preservation treatment:

  • Applying chemical preservatives to permeable timbers
  • Inserting boron rods into resistant or extremely resistant timber

If your timber requires preservation treatment, we have the skills, tools, and experience to get the job done right. We will identify the best treatment for your specific timber, and expertly apply the preservative with no mess or hassle. You’ll have peace of mind that your timber will last for many years to come.

Book a property survey through our online form or by calling us at 0800 048 9488!

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