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Green or Brown Treated Timber?
Green or Brown Timber, what's the difference?
Treated timber is wood that's been through a preservation process to protect it against rot, fungal decay and wood-boring insects, essential for anything used outdoors. At Walford Timber, we use a process called tanalising: timber is loaded into a sealed chamber and a preservative is forced deep into the wood under vacuum and pressure, rather than just brushed onto the surface. This gives far longer-lasting protection than a surface treatment alone, and it's why tanalised timber can carry guarantees of 10–15 years against decay.
Both green and brown treated timber will weather, initially to a honey brown colour before finishing up silvery grey unless stains or paints are applied.
So why do we give you the choice of green or brown treated timber and what does this actually mean?
As you can see from the image to the right, one has a light green tint and the other is a mid-brown colour.
The green colour is a by-product of the tanalising process and due to the fact that the main active ingredient is copper. The industrial copper-based preservative is applied in a vacuum/pressure treatment plant to extend the life of your timber.
Although the chemical is actually dark blue, the copper reacts with the air and oxidises, resulting in the familiar green tint of tanalised timber. The green colour is actually by coincidence, rather than by design.
It’s important to note, the shade will vary between all timber species and will change as the timber dries and is exposed to the sun. It is important to note it is not intended to be a decorative finish, it is just the result of the copper oxidising, an industrial process.
To create the colourway you want, you can stain or paint your timber once dry.
To achieve the brown colour we add a brown dye to the chemical mix. Exactly the same process is followed and you are left with a more traditional appearance to the timber rather than being a replacement for woodstains or paint. Because of the cost of the dye, brown treated timbers are marginally more expensive than green.
This is an industrial preservation process rather than a decorative finish but if you wish to achieve a particular colour or shade, woodstains and paints can be applied to the tanalised timber once it’s dry.
All tanalised timber left to the elements will fade over time, initially to a honey-brown colour, and then to a silvery grey.
Top Products Available In Green or Brown Timber
Common Questions About Treated Timber
What’s the difference between treated timber and tanalised timber?
‘Tanalised’ simply refers to timber treated using the Tanalith preservative system under vacuum pressure, it’s a specific, trademarked type of pressure treatment, not a separate category. All tanalised timber is treated timber, but not all treated timber is tanalised (some is treated by simpler dip or brush methods, which don’t penetrate as deeply or last as long).
What is treated timber used for?
Anywhere timber is exposed to the elements or ground contact: fence posts, gravel boards, decking, sleepers, gate posts and outdoor structural timber. The pressure-treatment process is specifically what makes softwood, which would otherwise rot within a few years outdoors, viable for long-term outdoor use.
Can you paint or stain tanalised timber?
Yes. Once the timber has fully dried out after treatment, it can be painted or stained like any other wood. We’d recommend waiting until it’s dried through (the green or brown colour will have faded slightly) before applying any finish, so the paint or stain adheres properly.
How long does tanalised timber last?
This depends on the timber’s end use and treatment class, but our PermaTimber® range, for example, carries a 15-year guarantee against fungal decay and wood-destroying insects. Ground-contact timber (like fence posts) is treated to a higher standard than timber that won’t touch the soil, since it’s at greater risk of decay.
Is tanalised timber safe to handle?
Yes. Modern tanalising preservatives (like the copper-based Tanalith system we use) are designed for safe handling once the timber has dried, and are widely used in residential fencing, decking and garden structures across the UK. As with any treated wood, it’s sensible to wear gloves when cutting it and avoid burning offcuts, since burning can release the preservative compounds.