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Treatment prolongs the life of H2 and H3 timber

Treatment prolongs the life of H2 and H3 timber

Wet weather across much of Australia and supply difficulties may leave partly built homes waiting for weeks or even months for roofs and walls.

“We’ve seen a lot of mould on building frames this year,” says Craig Kay, national product engineer at Tilling.

However this isn’t an issue with the treatment: framing timbers are almost always designed to be protected from the weather and contain H2 preservatives, intended to prevent borer and termite attacks.

In the big wet, says Kay, “There have been a lot of mould issues on frames made of all sorts of materials, plus other problems we don’t normally get. In a building frame, you tend to treat against insect attack, not against mould, because these timbers are meant to be protected inside, above ground.”

The timber can be performing exactly for what it was designed to do, but if circumstances change, or it’s used in the wrong application or not maintained appropriately, it can still have issues.

Australia is lucky when it comes to timber treatment. A comprehensive but practical regulatory framework is paired with a large amount of industry expertise and an active industry organisation – the Timber Preservers Association of Australia (TPAA) – that keeps regularly updated information available to all parts of the industry and public.

Wood is a natural product. If you want it to behave in the way you expect it to, then you can’t leave the timber out in the rain for months. You’ll need to get a roof on your frame next week, not in the next three months.

Koppers Performance Chemicals is a leading supplier of timber preservative chemicals and supplies a wide range of treatment options to timber treaters.

According to Koppers, almost all of the failures that occur happen because the product isn’t appropriate for the application or it’s not being used properly. You don’t use LOSP-treated timber in ground. You don’t use H2F blue timber in your decking structure outside, or H3 treated timber in ground-contact applications, or within the recommended clearance of the ground. When timber is used as recommended, the preservatives work.

Another common example of where failure can occur, is due to treated timber used externally being cut, and then not resealed correctly. Like in H3 or H4 applications, especially products like sleepers. Cutting timber, even partially, cutting out notches or drilling holes, may expose some untreated heartwood, which can then make those areas now vulnerable to decay. Koppers recommend that any treated timber product used in outdoor applications be resealed with a recommended product if cut. NHS sells products such as Ecoseal 300g for above ground application and Enseal for below ground applications.

While treatment hazard classes (H1–H6) describe the level of treatment or level of protection that must be applied to the wood, different timber species treated to the same hazard class will still retain the natural characteristics of each species (strength, stiffness, hardness etc.), meaning that, most of the time, selection or substitution requires much more than simply looking for a timber with a particular treatment level, or look, as some species may be more prone to surface checking for example.

Add to that some of the less-common treatments on the market, such as thermal modification and resin impregnation, which do affect some characteristics and the situation can be less straightforward.

So generally, the timber will not have failed but may be it looks weathered. The preservative is still working, and the timber is still doing its job, but you might not have the look you want anymore. It might be a different timber, or a less exposed position that was required.

It’s almost always about ongoing maintenance of the coating– which falls on the client for upkeep.

If some steps are omitted, then weathering can start to degrade the timber and that can speed up the ageing process. For structural timber, that’s obviously a concern, but the visual impacts will show up faster and for architectural jobs that rely on a lot of visual appearance of the timber, that will impact the final build and can impact that client’s willingness to use that timber again on their future projects.

Treatment does come with a warranty, however timbers don’t, and we instead talk about durability classes 1, 2, 3 and 4, which come with an expectation, but it’s not a guarantee.

Something to ponder, if you take a thick piece of H3 timber with a penetrative treatment and was going to cut into or mould into a profile, it voids the warranty, because you are taking most of the treatment off. There is still treatment left in the timber, making it more durable than the alternative without a treatment, but with no warranty, so be sure to understand that trade off.

 

Source: Timber Trader News