| H1 | Inside, under cover, protected from the weather and well ventilated | Insects | LOSP |
| H2 | Inside, under cover, protected from wetting, no leaching | Insects and termites | LOSP |
| H2F | Inside, under cover, protected from wetting, no leaching, envelope treated, South of the Tropic | Insects and termites | LOSP |
| H2S | Inside, under cover, protected from wetting, no leaching, South of the Tropic | Insects and termites | LOSP |
| H3 | Outside above ground, periodic wetting but where the timber can dry out, some leaching | Insects, termites and moderate decay | CCA, ACQ, Copper Azole, LOSP |
| H4 | In or on the ground subject to severe wetting and leaching | Insects, termites and severe decay | CCA, ACQ, Copper Azole |
| H5 | In or on the ground subject to severe wetting and leaching, with or in water | Insects, termites and very severe decay | CCA |
| H6 | In contact with sea water | Marine borers and decay | CCA |