Health and Safety

Taking care with materials, equipment and work procedures and dealing with hazards.

Working with treated timber

Timber treatment preserves timber but can also be hazardous to health.

On this page:

  • types of timber treatment
  • Boron preservative
  • LOSP preservative
  • CCA preservative
  • alternative timber preservatives
  • alternatives to treated timber.

Timber treatment prevents deterioration by insect or fungal attack and preserves the quality of the timber.

Unfortunately, the chemicals that are used to preserve timber can also be harmful to people.

Precautions must be taken by anyone working with treated timber including those who carry out the treatment and those who work with treated timber.

Building site teams should obtain safety data sheets from the producer or supplier of the treated timber. These data sheets give specific information about the care required in storing, using and disposing of the timber.

Types of timber treatment

The level of treatment selected must be appropriate for the intended use of the timber. The most commonly used preservatives for timber treatments are:

  • Boron compounds
  • CCA compounds (copper chromium arsenic)
  • LOSP (light organic solvent preservative).

All fine wood dust is hazardous – protection to eyes, respiratory system and skin must be provided and worn.

Boron preservative

Boron is a water-based preservative frequently used for H1.2 framing timber. It is commonly dyed pink (although where it is used for certain H3.1 applications, it is pre-primed in grey.)

Under normal conditions with good building practice, boron from boron-treated timber has no reported long-term health effects.

LOSP preservative

With LOSP, preservative chemicals are impregnated into timber with controlled vacuum processes. LOSP preservatives cannot be used for enclosed framing timber under B2/AS1.

Use and handling

  • Store in a well-ventilated, covered area.
  • Remove wrapping to allow vapour to evaporate.
  • Wear gloves and long sleeves when handling timber.
  • Wear safety glasses and a filter mask when cutting and sanding.
  • Work in a well-ventilated environment and carry out cutting, sanding and so on outside.
  • Avoid working with solvent-damp timber.
  • Always wash hands after handling LOSP timber.
  • Wash clothes separately if there is sawdust on them.

CCA preservative

CCA treated timber (also commonly called tanalised timber) contains copper, chromium and arsenic, which is a toxic chemical mixture but is relatively inert once fixed in the timber. However, it is not recommended in skin contact use such as children’s playground equipment and hand rails. Treatments such as alkaline copper quaternary and copper azole do not have the chrome and the arsenic but the higher levels of copper increase the corrosion potential with steel and galvanised steel fixings.

Use and handling

  • Carry out all cutting, sanding and so on outside.
  • Wear a filter mask, safety glasses and gloves when cutting and sawing.
  • Take particular care when the timber surface is wet or has crystalline chemical deposits on it.
  • Clean up (timber scraps, sawdust) thoroughly afterwards.
  • Dispose of waste to an approved (municipal) waste disposal area.
  • Do not compost or mulch waste.
  • Do not burn waste.
  • Wash your hands before eating, drinking or smoking.
  • Wash exposed areas of your body after working with treated timber.
  • Wash work clothes separately from other clothes.

Environmental effects

Small quantities of chemicals can leach out over time so it should not be used where it may come into contact with public drinking water.

Alternative timber preservatives

Other timber preservatives that are marketed as more environmentally friendly alternatives include:

  • copper azole-based (CuAz)
  • alkaline or ammoniacal copper quarternary-based.

These treatments are approved for used for H3.1, H3.2, H4 and H5 hazard treatment levels. They contain higher levels of copper than the CCA preservatives, which mean they are more corrosive to metals. Care must be taken when selecting fixings, and consideration must be given to run-off from timber onto other materials.

Alternatives to treated timber

Alternatives to using treated timber may include substitution with other materials where possible. For example:

  • use concrete piles, strip foundations, recycled hardwood (e.g. jarrah telephone poles) or concrete block retaining walls instead of piles or posts
  • use heartwood timbers such as western red cedar or redwood for weatherboards, decking, and so on instead of LOSP treated timber
  • use Douglas fir, Lawson cypress or kiln-dried radiata pine instead of boric-treated timber where the in-service moisture content will always be 18% or less.


Update: 07 March 2023