Treated Pine Hazard Classes


wdt_ID Hazard Class Exposure Treated Against
1 H1 Inside, above ground. Completely protected from weather and ventilated. Lyctid Borer
2 H2 Inside, above ground. Protected from Moisture Termites and Borers
3 H3 Outside, above ground. Can handle periodic exposure to moderate moisture Moderate Decay, Termites and Borers
4 H4 Outside, in-ground contact. Can handle severed weeting and leaching Severe Decay, Termites and Borers
5 H5 Fresh Water, Outside, in-ground contact. Subject to extreme moisture/wetting and leeching to severe wetting and leaching with or in fresh water Extreme/Severe decaying, Termites and Borers
6 H6 Marine Water. Subject to prolonged submersion in sea water Decaying and Marine Borers

Common types of Treatment


Light Organic Solvent-borne Preservative. LOSP is a solvent-borne preservative treatment of pine timber. The organic solvent takes the preservative into the wood and is drawn out in the last stages of treatment leaving the preservative in the wood. LOSP treated pine has long lasting protection against decay and insect attack. LOSP treated timber is great for appearance applications such as external joinery, due to it leaving the light coloured appearance unchanged after treatment.


Copper, Chromium and Arsenic salt. CCA is a water-borne preservative treatment of pine timber. CCA is pressure impregnated into the wood and has a high resistance to chemicals leaching out of the timber over time. This high resistance is due to the chromium which locks in the elements of copper and arsenic into the wood. The arsenic and copper elements protect from insect and fungal attack. Pine which has been treated with CCA is clean, odourless and has a slight green colour.


Alkaline Copper Quaternary. ACQ is a water-borne preservative treatment of pine timber. The ACQ treatment process is similar to CCA but is free of arsenic. Instead uses copper and ammonium compounds as agents against insect attack, fungi, termites and wood boring insects. After pine has been treated with ACQ its appearance can range from dark green to brownish green and can be stained or painted once dry.

Below are some links to helpful and informative websites

Wood SolutionsTPAA