Timber Treatment Classes H1 to H6 Explained
The H number on treated timber tells you where it can go.
In Australia, treated pine and some other timbers are marked with a hazard class from H1 to H6. The number tells you the conditions it's treated for.
| Class | Typical use |
|---|---|
| H1 | Inside, dry, away from insects such as borers |
| H2 | Inside, dry, protected from termites |
| H3 | Outside, above ground, such as decking and fence rails |
| H4 | Outside, in the ground, such as fence posts |
| H5 | In the ground or fresh water where it's critical, such as house stumps and retaining walls |
| H6 | Marine use in salt water |
Always check the product label and the maker's guidance for your use.
Safe handling
- Wear a dust mask and gloves when cutting treated timber.
- Don't burn treated timber offcuts.
- Check the treatment type before using it near food gardens.
General information only. Check the maker's instructions, and ask your council about approvals.
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