How do you maintain treated pine decking?

Just like any other type of decking timber, treated pine needs to be maintained. You cannot just build your decking and forget about it.

Depending on its coating, preservatives used, and state, it needs to be thoroughly washed and oiled at least once a year. If you want to stain it, you will have to do that annually, as well.

Image source: MK Home Design

Treated pine is different from hardwood decking timber because pine is actually softwood. It has been soaked in preservatives to obtain the properties necessary for timber that is used in outdoor conditions.

When processed in this way, treated pine has the properties of class 1 or class 2 hardwood decking. That is the highest resilience possible. This type of hardwood is resilient to termites, borers, fungi, rain and other negative influences.

However, treated pine lacks something else that hardwood has – the integrity of its structure. While the preservatives will make treated pine timber resilient to all these factors above, they will not make it resilient to slitting, blotching, bending and general loss of shape and form.

The nature of pine is to react to atmospheric changes, moisture, temperature, and humidity. This doesn’t stop just because it has been treated with preservatives.

Before you choose treated pine timber, consult a decking expert that you hire to do your decking. They have a lot of experience with different materials, so they will know what you can expect from your treated pine decking.

How Long Does Treated Pine Decking Last?

You can expect your treated pine decking to last over 30 years. However, now all treated pine is treated in the same way. The treatment the timber has received is marked from H1 to H6. Your treated pine decking needs to be marked at least H3. If you can opt for H4, that is even better.

The longevity of your treated pine decking depends on the thickness of your boards, the treatment level and whether it is in contact with the ground or not.

The lifespan of even the most resilient decking timber is reduced if it is touching the wood. The same situation happens with the treated pine. If it touches the ground, it will last a lot shorter than if it is only used as a decking cover.

Whether the treated timber should and should not be touching the ground is exactly the difference between the H3 and H4 levels of hazard endurance. Both of these levels give your timber the resilience to termites, borers, moderate to severe wetness and decay. However, only H4 gives it enough resilience to be in constant contact with the ground.

You may or may not have to stain your treated pine. It all depends on the preservatives that were used to treat the pine. First, let’s learn a bit about the types of treatment used for treated pine decking:

LOSP stands for Light Organic Solvent Preservative. It is the most natural and the least harmful of all the preservatives, but it also offers the lowest level of protection. LOSP can reach level H3, which is its highest level of protection. It uses some synthetic compounds as insecticides, but it uses white spirit as a solvent, making it less hazardous.

Copper Chrome Arsenate, or CCA, is just what the name says. The combination of copper, chrome and arsenic is very effective in protecting the timber, but it is also highly toxic. It still hasn’t been banned in Australia, but it is continuously deserted and replaced by healthier alternatives. Arsenic repels insects, copper deals with the fungi, and chrome binds it all to timber. The protection levels reach the highest H6.

Alternatives to CCA. The two most widely used alternatives are Alkaline Copper and Quaternary (ACQ) and Copper Azole (CA). They both contain copper, which is the main fungi repellent. They also have components that deal with the fungi that are resistant to copper.

The protection they offer reaches the level H5, which is still very good. H6 would mean that the decking can resist Marine borer and that is highly unlikely to be necessary in your backyard.

Can I Stain Treated Pine?

First, you need to know what type of preservatives are used on your treated pine decking. Then, you have to decide between water-based and oil-based staining if you still want to do it. Different treatments react differently, so here is what you need to keep in mind:

LOSP-treated pine decking – It is very important that you use primer on this type of decking. Moreover, you should run over your decking twice with the primer. LOSP-treated timber loves being oiled. That is the best maintenance for it. You don’t have to stain it, but if you want to, be extra careful not to use water-based decking stains. Moreover, you need to be very careful with the choice of your staining, so consult the manufacturer first.

ACQ and CA-treated pine decking – Since they provide a very high level of protection, treating them is not that necessary. However, if you don’t, your decking will not look nice. For maintenance, you need to scrub down this decking and let it dry entirely for a couple of days.

Check the weather forecast to catch a couple of rainless days so your decking can dry well. Oil it nicely, and you are good to go. Water-based stains can lock in moisture that will be fertile ground for mould.

CCA-treated pine decking – Due to the endurance this type of treatment offers, you can basically do whatever you like with it. Staining is not necessary at all.

As you can see, there are several possible problems with water-based stains. They can lock in moisture that then produces mould, which is next to impossible to eradicate.

Also, it may last longer than the oil staining, but it also ages badly. The only way to remove water-based stains is by paint stripper or sanding. On the other hand, oil stains need to be redone every year.

There is so much more to treated pine decking than just installation. However, if that hasn’t been done right, the maintenance will be the least of your problems. Always hire a professional decking installer and consult him before purchasing the decking timber.

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