Under the Environment Protection Act 2017 (the Act) and Environment Protection Regulations 2021 (the Regulations) all industrial waste must be taken to a place that can lawfully receive it. This includes sorting, resource recovery and disposal facilities.

This page sets out how to identify and dispose of most common types of treated timber when safe reuse is not possible. Timber treated with hazardous substances are now classified as priority waste. Disposal of priority wastes requires an assessment of the disposal category based on the substances used to treat the timber. Understanding the range and concentration of chemicals in timber can require sampling and further assessment which can be time consuming and costly.

About treated timber

Timber products are often treated with pesticides and other chemicals for protection from insects such as borers and termites, fungi that cause rot and decay, and weathering. These preservatives can create a risk of harm to human health or the environment if they leach into the ground and contaminate soil or groundwater. The most common types of preservatives used include:

• water based preservatives, for example, copper chrome arsenate (CCA) and boron-based preservatives, used in a wide range of applications
• light organic solvent preservatives (LOSP), for example, copper naphthenate (CuN) and tributyl tin naphthenate (TBTN), used for timber treated in its final shape and form, including high-value joinery such as balustrades and fascias.

Treated timber has many uses, including but not limited to; house and deck framing, flooring, interior and exterior joinery, cladding, garden furniture, trellises, pergolas, picnic tables, exterior seating, patios, decking, lattice, handrails, stairs, retaining walls, poles, stumps and fences.

The information on this page does not apply to oil-borne preservative treated timber

In certain circumstances, the preservative used to treat timber will be oil-borne (creosote and pigment emulsified creosote (PEC)). This includes treated timber used for heavy duty construction and in the marine environment, such as marine piles, utility poles and rail sleepers.

Timber treated with oil-borne preservatives requires further risk assessment to determine which landfill it can go to. This may involve categorisation against the criteria set out in Schedule 6 of the Regulations and the Waste disposal categories – characteristics and thresholds (publication 1828). Contact EPA for further guidance.

Waste classification for timber waste

Timber waste can be classified differently depending on whether it has been treated or not, as indicated by the paired mirror codes ending in either -H or NH. The classification criteria for determining which mirror code to use is set out in Table 1 of the Waste classification assessment protocol (publication 1827).

Treated timber is classified as a priority waste under the Act and Regulations with the mirror code K310-H (timber treated with hazardous substances, including sawdust), with this criteria:

• Timber, wood or material derived from wood (including sawdust and engineered wood) that is likely to have been treated or chemically altered or coated with a hazardous substance, including paint, varnish, preservative or fumigant to enhance the performance of the original wood. 

Note: excludes timber, wood or material derived from wood which has been treated with heat only.

Learn more about your priority waste duties.

Where to dispose of my treated timber

When consigning priority waste for disposal, the disposal category must first be identified to find out which landfills that waste can go to. EPA acknowledges the difficulties this could pose to many construction and fencing businesses, as well as contractors when dealing with treated timber waste.

As such, EPA can advise that treated timber, other than those treated with oil-borne preservatives, can be accepted at municipal (putrescible) waste landfills under the disposal category industrial waste.

Treated timber should not be disposed of at solid inert waste landfills.

Acceptable as disposal category industrial waste at municipal (putrescible) waste landfills only

• Fencing
• Flooring and decking
• Building and construction timber
• Furniture and seating
• Other water-based preservative and LOSP treated timber

Further risk assessment required

Categorise as per Schedule 6 and Waste disposal categories (publication 1828) to determine which landfill it can go to or contact EPA for further guidance.

• Utility poles
• Railway sleepers
• Marine piles
• Other oil-borne preservative treated timber