Treated pine decking can last for over 30 years when properly treated – this means the hazard level is at least H3, ideally H4. The lifespan of the treated pine depends on whether it is touching the ground, how thick the poles or planks are and the hazard level of its treatment.
Namely, the treated pine will last longer if it doesn’t touch the ground. Even in the case of the strongest hardwood, the lifespan of the timber decking reduces if the timber is in contact with the ground. There are many treatments that will increase the pine's durability, but if the ground contact can be avoided, it is better that you do so.
The strength of the treated pine is measured with special machinery, just like every other timber. Again, just like any other timber, this measurement is incomplete without the opinion of an expert. That is why, if you are thinking of building treated pine decking, you should talk to timber decking experts and get them to asses the timber and your project.
This is the treated pine decking that is treated for certain environmental hazards. It is also the lowest level of treatment that you should go for when building decking with treated pine timber.
Treated pine decking of H3 is not suitable for in-ground use. This means that this type of timber can be used outside, but only if it doesn’t touch the ground or is driven in the ground.
Image source: Advanced Timber
Environmental conditions that this type of treated pine can sustain are leaching and moderate, occasional wetting. This means that your H3-treated pine decking will hold well under the rain unless it rains all the time, which is not the case in Australia.
Timber leaching is the process in which the natural oils and tannins get oozed to the surface of the timber. It happens when the timber comes in contact with the moisture. H3 treatment protects your decking from this. While it is not dangerous, it can cause stains and discolouration of the decking timber.
While treatment cannot completely stop the natural process of decay, H3 will slow it down, and it will protect the treated pine decking from a moderate level of decay.
Also, it means that borers and termites will not be able to damage the construction, which is quite important, especially if your decking is elevated and poor construction may cause serious falls.
H4-treated pine decking is safe for both above and in-ground uses. H4 means that the timber is treated in a way that allows it to be used for most outdoor projects. As far as the environmental conditions are concerned, H4 offers protection from leaching and severe rains. Namely, this kind of decking timber will be able to sustain severe wetness.
Image source: Pine Timber Products
While it will be able to repel the termites and borers, it will also be able to protect the treated pine decking from severe decay. That means you can expect your treated pine decking not to rot for a long, long while.
H4-treated pine decking can be used in the ground, while H3-treated pine should not be in contact with the ground if you want to prolong its lifespan. The difference is in the chemicals used for the treatment of the pine timber.
Both of these treatments will protect the treated pine decking from the influence of termites and borers. To some extent, H3 will also ensure protection from wetness and decay. However, the H4 treatments will offer even stronger protection in wet environments and it will prevent even more decay.
While H3 treatment is mainly enough for the decking that doesn’t touch the ground, H4 is also used for the decking that touches the ground, but also for different fences, pergolas and even small timber walls, but only if they are not structural.
There are three types of treatments for the pine decking. The first are the oil based preservatives, the second are the water based preservatives and the last are solvent based preservatives. Here are the most commonly used preservatives, categorised according to their base:
| Oil Based preservatives | Water based preservatives | Solvent-based preservatives |
|---|---|---|
| Creosote, Pigment Emulsified Creosote (PEC) | Copper Chrome Arsenic (CCA) | Light Organic Solvent Preservative (LOSP) |
| Alkaline Copper Quaternary (ACQ) | ||
| Copper Azole (CuAz) |
Copper Chrome Arsenic (CCA) is slowly being abandoned because of its toxicity. It contains arsenic, which is a highly poisonous substance. While it is still legal in Australia, it is being replaced with other options. Provides from H1 to H6 level of protection.
Alkaline Copper and Quaternary (ACQ) offers protection from termites, fungi and decay. It is considered a safer variant from the CCA due to the absence of arsenic. Protection levels from H1 to H5.
Copper Azole also uses copper as a fungicide and azole as protection from borers and termites. It is another alternative to the CCA. The most commonly used Copper Azole is Tanalith E. Protection levels H1 – H5.
LOSP treatment offers the same protection as CCA, but it does it with much lower-impact preservatives and environmentally friendly components. Protection levels H1 – H3.
Creosote is not used in domestic treatments because of its distinctive features. It is made out of wood and coal and has a strong smell and tarry colour. It offers protection from borer termites, but also Marine borers.
| H1 | H2 | H3 | H4 | H5 | H6 |
|---|---|---|---|---|---|
| CCA | CCA | CCA | CCA | CCA | CCA |
| ACQ | ACQ | ACQ | ACQ | ACQ | |
| TanE | TanE | TanE | TanE | TanE | |
| LOSP | LOSP | LOSP |
Treated pine decking is an excellent, budget-friendly option that is becoming increasingly popular on the market. It has a nice colour that seasons well and since pine grows quickly, it is easy to find treated pine decking timber that comes from sustainable sources. What you need to do is find properly treated pine for your project and a capable decking expert to construct it.
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