Tanalised Timber: The Secret to Lasting Outdoor Projects?

Tanalised timber refers to wood that has undergone a preservative treatment process, specifically designed to protect it from decay, insects, and other forms of deterioration. The term “tanalised” comes from the proprietary brand name Tanalith, a type of wood preservative developed by Arch Timber Protection, although it is now commonly used to describe any timber treated with similar preservatives. This process extends the life of the timber, making it highly suitable for outdoor applications such as fencing, decking, and garden furniture.

1. The Tanalising Process

The process of producing tanalised timber involves several stages to ensure the wood is deeply penetrated by the preservative, making it resistant to environmental threats. The key steps include:

• Initial Preparation: The timber is first dried to reduce its moisture content. This allows the wood to better absorb the preservative during treatment. Kiln-drying is commonly used to achieve the desired moisture levels.
• Vacuum and Pressure Treatment: The timber is placed in a large cylindrical treatment vessel. Initially, a vacuum is applied to remove air from the wood cells. Then, the vessel is flooded with the preservative solution, which typically contains a mixture of copper, organic biocides, and sometimes borates. After flooding, the vessel is pressurised, forcing the preservative deep into the wood fibres.
• Final Vacuum: Once the treatment is complete, a final vacuum gets applied to remove any excess preservative from the timber’s surface. This step helps to minimise the risk of leaching when the wood is exposed to moisture.
• Drying and Fixation: The treated timber is then removed from the vessel and allowed to dry. During this period, the preservative chemically binds to the wood fibres, making it less likely to wash out over time. The drying process also stabilises the wood, reducing the risk of warping or splitting.

2. Benefits of Tanalised Timber

Tanalised timber offers several significant advantages, particularly for outdoor and structural applications where durability is crucial:

• Enhanced Durability: The primary benefit of tanalised timber is its increased resistance to rot, decay, and insect attack. This makes it ideal for use in environments where the wood is exposed to moisture or soil, such as in garden fences, decking, and outdoor furniture.
• Longer Lifespan: Tanalised timber typically has a much longer lifespan than untreated wood, often lasting 20 to 30 years or more, depending on the conditions. This longevity makes it a cost-effective choice for long-term projects.
• Low Maintenance: Due to its resistance to environmental factors, tanalised timber requires less maintenance than untreated wood. While it may benefit from occasional treatments with wood oil or stain to maintain its appearance, it does not need the frequent reapplications of preservative that untreated wood requires.
• Versatility: Tanalised timber can be used in a wide range of applications, from building structures like sheds and pergolas to creating garden beds and retaining walls. Its versatility and strength make it a popular choice for both DIY enthusiasts and professional builders.

3. Applications of Tanalised Timber

Tanalised timber is widely used in various outdoor and structural projects, thanks to its durability and resistance to harsh conditions. Common applications include:

• Fencing: Tanalised timber is often used for fence posts, rails, and panels, providing a strong and long-lasting solution that can withstand exposure to the elements.
• Decking: For decking projects, tanalised wood offers a durable surface that can resist rot and insect damage, making it ideal for high-traffic areas like patios and terraces.
• Garden Structures: Sheds, pergolas, and gazebos made from tanalised timber are not only aesthetically pleasing but also highly durable, standing up well to outdoor conditions over many years.
• Landscaping: Tanalised timber is used in landscaping for building raised garden beds, retaining walls, and even playground structures, offering both safety and durability.
• Agricultural Uses: In agriculture, tanalised wood is typically used for constructing livestock enclosures, farm buildings, and gates, where the wood’s resistance to decay and pests is particularly valuable.

4. Environmental and Safety Considerations

While tanalised timber is beneficial for its durability and longevity, there are some environmental and safety considerations to be aware of:

• Chemical Composition: The preservatives used in tanalised timber typically contain copper and organic biocides, which are effective against rot and insects. However, older formulations (no longer widely used) contained chromated copper arsenate (CCA), a compound that included arsenic. Today, modern tanalised timber uses safer, less toxic alternatives, but it’s still important to handle treated wood with care, particularly when cutting or sanding.
• Disposal: Because of the chemicals used in the treatment process, tanalised timber should not be burned, as this can release harmful fumes. Disposal should be done according to local regulations, often requiring the wood to be taken to a specialised facility.
• Environmental Impact: The environmental impact of tanalised timber is mitigated by its long lifespan, reducing the need for frequent replacements. Additionally, sourcing timber from sustainably managed forests ensures that the environmental footprint is minimised.

5. Care and Maintenance

While tanalised timber is designed to be low-maintenance, some care is recommended to keep it looking its best:

• Sealing: Although not always necessary, applying a water-repellent sealant can further protect tanalised timber from moisture and UV damage, helping to maintain its appearance.
• Cleaning: Regularly cleaning the wood with a mild detergent and water can help remove dirt and prevent the growth of mildew or algae.
• Staining or Painting: If you wish to change the colour of your tanalised timber, it’s possible to stain or paint it after allowing the wood to weather for a few months. Always use a product that is compatible with treated wood.

Conclusion

Tanalised timber is a robust, long-lasting material that offers significant advantages for outdoor and structural use. Through its specialised treatment process, it gains resistance to rot, decay, and insects, making it an ideal choice for projects exposed to the elements. While there are some environmental and safety considerations, the benefits of using tanalised timber, particularly in terms of durability and low maintenance, make it a popular and practical option for a wide range of applications.