If a timber species does not have the natural durability to withstand a desired use, the timber may be chemically treated to enhance its resistance to insect borers, termite attack, and rot. Chemical treatment is available in six levels to cover different levels of risk, for example hazard level 1 treatment is for insect borer resistance in internal environments while hazard level 6 prevents termite attack and rot in marine conditions.
Treated timber does not however, protect against weathering. To protect against weathering, regular coats of oils and paints must be applied.
Chemical treatment penetrates through the sapwood of timber most effectively. In softwood species, the treatment also penetrates through heartwood, however for hardwood, the treatment penetrates the sapwood only. Sawn hardwoods therefore cannot be chemically treated, and alternatively the appropriate natural durability class must be chosen for the specific conditions.
A variety of chemicals are used to achieve the different hazard class levels, which vary from water borne preservatives, light organic solvent borne preservatives and oil borne preservatives. Some are hazardous to touch and should be researched thoroughly before specification. For more information on Timber Treatment by www.timber.net.au , click here.
table courtesy of www.timber.net.au