Timber products are often treated, chemically altered or coated with hazardous substances. This can include paint, varnish, preservative or fumigant. These substances protect the timber from insects – such as borers and termites – and fungi that cause rot, decay and weathering.
Treated timber can be:
- timber
- wood
- other materials derived from wood, such as sawdust and engineered wood.
Engineered timber products can have additives that are harmful to the environment. These products include chipboard, medium-density fibreboard and laminated veneer lumber.
The most common types of substances include:
- water-based preservatives – for example, copper chrome arsenate (CCA) and boron-based preservatives
- light organic solvent preservatives – for example, copper naphthenate and tributyl tin naphthenate – used for timber treated in its final shape and form, such as high-value joinery like balustrades and fascias.
In certain circumstances, timber is treated with oil-borne preservatives (creosote and pigment-emulsified creosote). This type of treated timber is used for heavy-duty construction and in marine environments – for example, utility poles, railway sleepers and marine piles.
Treated timber waste can create a risk of harm to human health and the environment. This happens when these chemicals leach into the ground and contaminate soil or groundwater. The risk to human health mostly comes from the soil, where contamination can remain for some time. Burning treated timber also releases toxic substances into the air.
Treated timber can be used in:
- house and deck framing
- flooring
- interior and exterior joinery
- cladding
- garden furniture
- trellises
- pergolas
- picnic tables
- exterior seating
- patios
- decking
- lattices
- handrails
- stairs
- retaining walls
- poles
- stumps
- fences.
Treated timber and the law
The general environmental duty applies to the management of treated timber waste from both households and industry. This includes storage and handling.
Duties apply to managing land that is contaminated from treated timber waste. Learn more about contaminated land and groundwater.
If an incident harms or threatens to harm human health or the environment, you must report it as soon as you become aware of it. If you're responsible for a pollution incident from your waste activities, the duty to take action to respond to harm from a pollution incident may apply.
Timber waste is classified differently depending on whether it has been treated or not. This also determines where you can dispose of it. To learn more about classifying treated timber, visit Manage and dispose of treated timber.
In some cases, businesses need a F01 – Timber preserving works development licence to operate a timber preserving works.
Our role in treated timber
We regulate how treated timber waste is managed, including its:
- transport
- storage
- disposal.
Learn more about managing industrial waste.
Impact of treated timber waste on your health
For information about CCA-treated timber and your health, visit Copper chrome arsenate (CCA) treated timber(opens in a new window) on the Better Health Channel.
Refer to Ash from copper chrome arsenate (CCA) treated timber to learn about:
- collecting and disposing of ash from CCA-treated timber after a fire
- protecting your health when collecting ash.
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