Shelton Timber Treatment Co are able to supply contract treatment of pine products and are large contract treaters of pine throughout Victoria. This service allows the customer to supply their own timber to be processed.
Chemicals are used to impregnate the wood cells and make them resistant to decay, insects, weather, or fire. Treatments assist in ensuring adequate service life pine timber.
Chemical treatment adds to the cost of the timber, but can significantly increase its serviceable life. When used in environments in which there are known biological hazards, it is cost-effective to specify treated timber and expect a longer service life and a lower cost maintenance schedule.
The preservative treatment of timber or timber products involves the introduction of stable chemicals into the cellular structure of timber that protect the timber from hazards such as wood destroying organisms including fungi and insects.
To determine whether the use of preservative treated timber is required, consider the following issues:
Preservative treatment of timber is primarily concerned with protection of the sapwood. It is not possible to effectively treat heartwood in most species, as heartwood cells contain resins and other extractives which prevent the uptake of preservative solutions. The wide sapwood bands of the major plantation softwoods (radiata, slash, hoop pine) can be effectively treated with preservatives.
Preservative treatment level is specified using the same hazard level scale used to indicate hazard level.
A suite of standards made specifically for the timber treatment industry gives chemical retention rates and depth of penetration in order to satisfy requirements for the relevant H level of treatment.
Different processes of forcing the chemical into the wood give slightly different depth of penetration, but in general, the depth of penetration of the chemical may not change much with increasing levels of treatment using the same process. Increasing H levels have a requirement for increasing chemical retention rates (gms of chemical bonded to one kg of wood)
CCA – (Copper, Chromium and Arsenic salts) impregnates the timber with water and salts. CCA is pressure impregnated and designed to react with the wood cell components so that the active elements, copper (Cu), chromium (Cr) and arsenic (As) are fixed into the wood's structure. The arsenic component protects the sapwood from insect attack, the copper and arsenic from fungal degrade, while the chromium component chemically locks the elements into the timber, offering high resistance to leaching. Because the treatment is resistant to leaching, it can be used on timber that will be exposed to the elements or used in-ground.
There are a number of different formulations of CCA commonly used by the Australian timber industry. Each has different production requirements, but all of them have equivalent performance for a given H classification. The treatment is free of odour and so is suitable for use in enclosed spaces or for indoor applications; however, the treated timber has a green appearance, which may detract from its appearance in some applications. The treated product has minimal release of volatile components and as the salts are “fixed” in the timber, they are safe to handle or work.
After treatment, the timber commonly has a moisture content that would class it as unseasoned. In order to give the treated timber dimensional stability, it must be re-dried. This process can decrease its strength a little, and invariably adds a little to the cost of the timber.
| Hazard Level | Service Condition | Biological Hazards or Pests | Typical Applications |
| H4 | In ground or ground contact, outside | Fungal decay termites & Borers | Fence posts, sleepers, landscaping, garden edges & boxes |
| H5 | In ground or ground contact, outside, critical or structural use. | Fungal decay, termites & Borers | Engineered retaining wall, building poles |
Treated timber is highly versatile. It is used extensively both inside and outside houses and commercial buildings, and in landscaping.
Treatment is carried out by impregnation of the timber, under vacuum and pressure, with tanalised preservatives in accordance with Australian Standards.
After treatment and redrying the tanalised preservative becomes substantially part of the cellular structure of the timber. It can not be removed by weathering, rain, wetting, soaking or scrubbing. The treatment can never be washed out.
The preservative chemicals are toxic to insects and fungi, which is, of course, their purpose. Provided that common sense precautions are observed, preservative chemicals do not present a hazard to humans when fixed in the dried timber.
Sometimes a white powder will appear on the surface of the timber. This is mostly Sodium Sulphate, a harmless substance which, if necessary, can be simply brushed or hosed off.
Under normal circumstances, plants and animals in contact with Tanalised treated timber will be perfectly safe. Care should be taken with certain specific applications such as birdcages, beehives and fishponds. For further information contact TPAA.
Tanalised treated timber must never be burnt in barbeques, household fireplaces, wood burning stoves or in confined spaces.
The best method of disposal is to take the unwanted treated timber to the tip or bury it.
Tanalised treated timber can be planed, chiselled, nailed or drilled just as easily as untreated timber. Nails, plates and bolts should be hot-dip galvanised.
Dry Tanalised treated timber can be painted or stained in the same manner as untreated timber.
