Timbers in schedules A, B and C are allocated individual natural durability ratings for above-ground and in-ground situations, in accordance with AS 5604-2005 Timber—natural durability ratings.

In-ground durability ratings system for heartwood:

    Durability class 1. In-ground life expectancy >25 years
    Durability class 2. In-ground life expectancy 15 to 25 years
    Durability class 3. In-ground life expectancy 15 to 25 years
    Durability class 4. In-ground life expectancy 0 to 5 years