Treated v Untreated Timber: Which To Choose For Your Construction?

When it comes to enhancing the finished standard of your construction project, the materials you use play an important role. Not only do you need to think about their dimensions, but you also need to consider how protected they are against the environments you’ll use them in. In the world of wood, whether timber is treated or untreated makes the biggest difference to its resilience. So, what’s the difference between treated and untreated timber – and which should you choose?

In this article, we’ll answer these questions and more.

What is untreated timber?

Untreated timber is basically just wood in its natural state. After being cut from the tree, it’s separated into boards and stacked with layers of separation in between. This facilitates the circulation of air, which dries the timber boards. They can also be kiln-dried, if for some reason the boards’ moisture levels need to be reduced further than is possible by air circulation alone, they can be kiln-dried. While this process can be lengthy, it’s essentially natural – the only agents used are air and heat.

What is treated timber?

Treated timber undergoes a more artificial and rigorous process. First, the timber boards are placed into a vessel, which a vacuum sucks all the air out of. The vessel is then filled with a chemical called a preservative and the vessel is pressurised. This forces the preservative into the gaps that were formerly filled by air.

The pressurisation process is an integral part of what makes treated wood what it is – but it wouldn’t have any meaning without the preservative itself. You see, the preservative is what makes the treated timber highly resistant to insects and decay. After being pressure treated with preservative, the timber has much-needed protection from common wood pests, such as:

Protected against insects such as:

  • Common Furniture Beetle
  • Wood boring weevil
  • Death Watch Beetle
  • House Longhorn Beetle
  • Termites

It’s also safe from common sources of decay, including Cellar Fungus, Pore Fungus, and Dry Rot.


What are the main differences between treated and untreated timber?

Durability and usability are the two main differences between treated and untreated timber.

  • Durability

Since untreated timber is left in its natural state, it remains vulnerable to the environment its used in. Treated timber, on the other hand, is shielded from the damage caused by wood-boring insects and decay. This makes it especially suitable to be used in outdoor building projects, where contact with soil and other moisture-laden surfaces is likely to be high. And whether used indoors or outside, it’s likely to last much longer.

  • Usability

However, the far greater durability that treated wood offers detracts from its usability. Because it’s laden with chemicals, inside and out, it’s necessary to wear personal protective equipment whenever handling or working with treated wood.

Relatively speaking, working with untreated wood is less hassle. Sure, you’ll still need to wear protective goggles to guard against woodchips – but at least there aren’t any dangerous chemicals to worry about. Its preservative-free surfaces are also easier to paint or stain than that of treated wood.

Choose the better timber for your project

If you need a durable wood for an outdoor building project, then treated wood is the better option. Its reduced vulnerability to insects and decay – and resultant longevity – are well worth the extra precautions you’ll need to take when working with it. And even though it’s more hassle to use than treated timber, it’s far better than heavy-duty alternatives like rock, concrete, or metal. But for any project that doesn’t involve placing wood in moisture-rich environments, untreated wood is likely the better choice.