Types of Timber Treatment

Timber treatments

Timber has it quite rough; it’s under constant attack from fungi, insects and the weather. Were it not for the treatment it has,  the timber that makes up your deck or pergola would  quickly rot away. Wood treatments effectively protect timber from these harmful elements that can cause damage, rot and decay.

There are different types of timber treatments and each one corresponds to a specific type of threat to the timber. Some treatments work well against termites, others protect against borers, while others repel rot-causing fungi. All timber must be classified using a Hazard Level scale that prescribes the kind of treatment suited to the purpose for which the timber will be used. Our page on Hazard Levels and Stress Grading describes this in detail. The different treatments use different preservatives and each type of preservative has distinct penetration patterns and retention characteristics.

Water-Bourne Preservatives

These preservatives are dissolved in water and then absorbed into the timber when it is soaked in the solution.

  • Copper Chrome Arsenate (CCA) protects timber from a wide array of threats, including rot, fungi, termites and other wood-boring insects. It is concocted from copper, chromium and arsenic. The copper prevents rot while the arsenic wards off insects. Chromium binds these two together into an insoluble compound that does not leach out of the timber. CCA-treated timber is designed to be used in outdoor areas, particularly where there is high moisture and lots of insects.
  • Alkaline Copper Quaternary (ACQ) also uses copper to protect against rot and fungal attack. Ammonium Quaternary functions as the pesticide. Timber treated with ACQ possess most of the same qualities as CCA-treated timber, and so are also suitable for outdoor and in-ground applications.
  • Tanalith E (or Copper Azole) also uses copper as the fungicide and Azole as the pesticide. Timber treated with this have most of the properties of CCA-treated timber, and it, too, can be used for in-ground applications.

Check out our Timber Treatment Information page to learn more about these different treatment options.


Instead of being dissolved in water, the chemical components of Light Organic Solvent Preservative (LOSP) are dissolved in (as the name implies) an organic solvent. LOSP timber has lower impact on the environment compared to CCA-treated timber, but is just as suitable for in-ground applications.

Softwoods stock a huge range of LOSP timber. Since CCA treated pine has been phased out for use in areas where children could come into frequent direct contact with the timber – we no longer stock any CCA decking and sell only LOSP treated handrails. We only use CCA timber for purposes that are safe and fully government approved.

For more details on LOSP, visit our LOSP Timber page.

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Attached gable pergola with timber liningIronbark deck over sloping site with inbuilt stairs and stainless steel balustrade

Softwoods is a family owned South Australian company that has been trading for over 30 years.


We understand that making changes to your home is a major and important thing, and we take care to understand that every project that we handle should be done with as much care as we would expect is used in our own homes. Learn more about Softwoods.

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Croydon, SA

573 Port Road
West Croydon SA 5008
Corner Rosetta Street

(08) 8346 1499

Modbury, SA

493 Wright Rd
Modbury SA 5092
Corner Wright & McIntyre Roads

(08) 8396 4044

Lonsdale, SA

28 O'Sullivan Beach Road
Lonsdale SA 5160
Corner Dyson Road

(08) 8384 5133

Perth, WA

Suite 15 Plaistowe Mews
102 Railway Street
West Perth WA 6005

1300 737 465