Timber Treatment in Australia and What it is Used For

Timber Treatment in Australia and What it is Used For

Posted by Daryl Schmidt on 21st Feb 2022

TIMBER TREATMENT LEVELS

From the Timber Preservation Association Australia - http://www.tpaa.com.au/

According to Australian Standard AS/NZS1604 parts 1 to 5, any product claiming to be preservative treated must be branded as specified in the standard. An important part of the brand is the Hazard Class, which indicates the service conditions to which the product is exposed and the level of treatment or level of protection that must be applied to the wood.

The Hazard Classes have been defined as follows:

Hazard ClassExposureService conditionHazardExample uses
H1Inside above groundCompletely protected from the weather, well ventilated and protected from termitesBorersSusceptible framing, flooring,
furniture, interior joinery used across Australia
H1.2 **Inside above groundCompletely protected from the weather, but with possible exposure to moistureBorers and decayWall framing
H2Inside above groundProtected from wetting, no leaching.Borers and termitesFraming, flooring, furniture, interior joinery used across Australia
H2FInside above groundProtected from wetting, no leaching.Borers and termites(Envelope treated) framing used south of the Tropic of Capricorn
H2SInside above groundProtected from wetting, no leaching.Borers and termitesFraming used South of the Tropic of Capricorn
H3Outside above groundPeriodic moderate wetting and leachingModerate decay, borers and termitesWeatherboards, fascias, pergolas, framing etc.
H3A ##Outside above groundPeriodic moderate wetting and leachingModerate decay, borers and termitesWeatherboards, fascias, pergolas, framing etc. – under a regularly maintained paint coat system
H3.1 **Outside above groundPeriodic moderate wetting and leachingModerate decay, borersWeatherboards, fascias, pergolas, framing etc. – under a regularly maintained paint coat system
H3.2 **Outside above groundPeriodic moderate wetting and leaching more critical end usesModerate decay, borersAll H3.1 uses plus structural and decking
H4Outside ingroundSevere wetting and leaching noncritical applicationsSevere decay, borers and termitesFence posts, retaining wall less than 1 m high, landscaping timbers.
H5Outside inground with or in fresh waterExtreme wetting and leaching, critical applicationVery severe decay, borers and termitesPiling, house stumps, power poles cooling tower fill, building poles, retaining walls more than 1m high
H6Marine watersProlonged immersion in sea waterDecay and marine wood borersBoat hulls, marine piles, jetty cross bracing, jetty landing steps.

## Applies to one preservative system used in Australia **Applies in New Zealand only