Pressure Treated Timber vs Untreated: Which Should You Buy?

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Curious about the difference between pressure treated timber and untreated timber? In this blog post, we’ll break it down for you – explaining how they differ and helping you decide which option is best for your upcoming project.

What is Pressure Treated Timber?

Pressure treated timber is wood that has been infused with preservatives to increase its durability, particularly for outdoor use. The treatment process typically involves three steps:

1. The timber is placed inside a large, sealed cylinder.
2. A vacuum removes the air, then preservatives are forced deep into the wood under high pressure.
3. These preservatives then protect the timber against rot, decay, insect damage, and general weathering.

Our Range of Tanalised Timber

At Park Timber, most of our timber products are treated with Tanalith E, a water-based preservative that provides lasting protection. The treatment involves a pressure-impregnation process, where Tanalith E is forced deep into the wood to help safeguard the timber.

Tanalith E, which contains copper and organic biocides, is more environmentally friendly than many older timber treatments, such as those based on arsenic or chromium. While it does have some environmental impacts, it is one of the more modern and tightly regulated preservatives, offering good performance and relatively low toxicity risks when used and disposed of correctly.

What is Untreated Timber?

Untreated timber is simply wood in its natural form – cut and dried without any added preservatives or chemicals. Unlike pressure treated timber, it hasn’t undergone any protective timber treatment. This makes it perfectly suitable for indoor projects, but if used outdoors, it can be susceptible to damage.

Pros and Cons

Both tanalised timber and untreated wood have their pros and cons, but the key thing to remember is that each is suited to different types of projects.

Pros of Treated Timber

• Durability: Highly resistant to rot, decay, and insect damage – ideal for outdoor use.
• Lifespan: Depending on exposure and maintenance, treated timber typically lasts longer than untreated timber.

Cons of Treated Timber

• Cost: Slightly more expensive due to the timber treatment process.
• Safety: Contains chemicals, so safe handling is important (e.g. wearing gloves or a mask when cutting or sanding). Modern treatments are generally safe, but protective gear is still recommended.

Pros of Untreated Timber

• Lower Cost: Usually cheaper than treated timber and more widely available.
• Natural Appearance: Retains its natural grain and colour, making it easier to stain, paint, or leave unfinished. With no added chemicals, it’s also safer for indoor use.

Cons of Untreated Timber

• Less Durable: More prone to rot and insect damage – best suited for indoor or sheltered projects.
• Shorter Lifespan: Doesn’t last as long as treated timber, especially when used outdoors.

Which Should You Buy?

Pressure treated timber is the best choice for outdoor use. It’s ideal for projects such as decking, fencing, landscaping, and other outdoor structures where the wood will be exposed to moisture and the elements. The treatment helps protect the timber, giving it a much longer lifespan.

Untreated timber, on the other hand, is better suited for indoor projects such as furniture, interior décor, sheltered joinery, and craft work. It should only be used in environments where it won’t be exposed to constant moisture or direct contact with soil. Its natural appearance and chemical-free properties make it a safer and more versatile option for interior use.

Maintenance Tips

Treated timber often has a greenish tint or a visibly treated appearance, which some people choose to stain or paint for a more attractive finish. To keep it in good condition and extend its lifespan, it should be sealed or re-stained every few years. This helps maintain both its appearance and resistance to weathering.

Untreated timber requires more care if it’s used outdoors. Applying protective oils, paints, or sealants will help shield it from moisture and sunlight, preventing warping, rot, and discolouration over time. Regular maintenance is key to preserving its natural beauty and structural integrity.

Conclusion

If you’re planning an outdoor project and want durable, high-quality materials, our tanalised timber is a great choice. Its enhanced resistance to rot, decay, and insects makes it ideal for long-lasting structures like decking, fencing, and garden features. To explore options that suit your project, check out our full range of timber products available online.