Coatings: An Essential in Decking Today

Decking Coatings For Lasting Results

Last month I wrote in detail about choosing a decking product. I mentioned the various products that are on the market and referred particularly to the shrinkage/ expansion rates of each species.

However, I want to clarify that the ratings mentioned in that article were sourced from the book “Wood in Australia.” These ratings might have been established some years ago and were likely based on larger, older growth trees. In contrast, most decking products available today are manufactured from smaller, younger regrowth trees. Consequently, modern decking products contain a higher proportion of reactive sapwood, making them more susceptible to changes in moisture content as seasons shift. In other words, many contemporary decking products are more prone to experiencing dimensional changes with varying moisture levels.

“(…) Modern decking products contain a higher proportion of reactive sapwood, making them more susceptible to changes in moisture content as seasons shift.”

Sapwood: Some Australian species, like Spotted Gum, can be vulnerable to attacks from the Lyctis Borer. Therefore, many decking producers treat this particular species to safeguard the susceptible sapwood against insect infestations. It’s crucial to note that such treatment only penetrates the open-celled sapwood and doesn’t reach the closed cells of the more durable heartwood.

“It’s crucial to note that such treatment only penetrates the open-celled sapwood and doesn’t reach the closed cells of the more durable heartwood.”

The attached decking photo clearly shows the difference between sapwood and heartwood. The open cells of sapwood readily absorb moisture, while the closed cells of the waterproofed heartwood showcase how moisture beads up after application of an oil-based coating.

I must emphasise that while treatment effectively protects sapwood from insect attacks, it doesn’t prevent potential board movement. This is where a high-quality oil-based coating proves invaluable by minimising moisture content fluctuations and, consequently, reducing board movement. Coatings like Cutek or Integrain not only penetrate the wood but also provide waterproofing. You can tell that this has occurred when the product’s surface beads up when exposed to rain. Another crucial aspect of a good oil coating is its ability to diffuse into the wood, rather than just sitting on the surface.

“Another crucial aspect of a good oil coating is its ability to diffuse into the wood, rather than just sitting on the surface.”

Maintenance

Like most outdoor products, maintaining your decking is essential. One sign of effective maintenance is when the decking continues to display moisture beads when subjected to rain.

Colours

Some consumers prefer their decking to weather and grey naturally over time. This desire for a weathered look doesn’t mean you can’t use an oil coating. A natural coating will eventually weather the wood but still offer waterproofing protection and display moisture beads, as mentioned earlier. If you wish to maintain a particular tint, you can add a UV stabilizer, but keep in mind that this will require periodic recoating.

In my previous article, I reserved comments about Merbau until the end. Merbau is predominantly sapwood-free, consisting mainly of durable heartwood. However, it’s notorious for causing tannin stains. Here, a high-quality oil-based stain can be used to mitigate this issue, especially when Merbau is used in proximity to concrete paving.

Suggested Procedure

Coat all surfaces of the boards before installation. Be aware that much of the tannin bleeding occurs from the end grain, so make sure to thoroughly apply a coat to the trimmed ends before installation. After installation, apply another coating to ensure comprehensive protection.

It’s worth noting that Blackbutt is also prone to tannin stain bleeding.

Ordering Advice

I strongly recommend purchasing pre-coated decking products from the Bowens warehouse. Although it may involve an additional cost, it saves a significant amount of time during installation. Additionally, procure tins of the same product, as applied in the factory, for use on trimmed ends.

Summing up: In my opinion, coatings are essential to address the challenges posed by the less mature wood products available today. Feel free to reach out for advice at 0412550740.