Hazard Class Description

Look for the "hazard class rating" on each stick of timber. The hazard class rating H1 to H6 tells you the level of treatment you need for the job in mind.


The treatment level for low hazard situations where timber is not exposed to the weather. Its major use is for framing timber and interior linings. This is split into two categories.


Timber used in situations protected from the weather, dry in service and where resistance to borer only is required.


Timber used in situations protected from the weather but where there is a risk of moisture exposure conducive to decay.


This level is similar to H1 but includes an insecticidal treatment to protect against termite attack for use in Australia.


For moderate decay situations where timber is exposed to the weather but is not in contact with the ground. This is also split into two categories.


Timber used outdoors above ground, exposed to the weather – generally in non-structural applications; i.e. fascia boards, weatherboards.


Timber used outdoors above ground, exposed to weather or protected from the weather but with a risk of water entrapment; i.e. decking, fencing and pergolas.


Used in high decay areas such as ground contact or fresh water. Generally used for fence posts and landscaping timbers.


Used for severe decay hazard risks such as ground contact where conditions of severe or continuous wetting may occur. End uses for this hazard class are house piles and poles, retaining walls, crib walling and horticultural supports.


This hazard class is for marine use. Wharf piles and fenders, marine and jetty components regularly immersed in seawater or estuarine ground.