“Treated pine” can mean many things, but at its simplest, it means that the pine has been treated in some way to extend its life. Untreated pine rots away quickly – in less than a year in some cases – and can also attract fungus and termites, while treated pine can last for thirty or forty years.
Treated pine – arsenic and CCA
CCA stands for ‘Copper Chrome Arsenate’ and has been used as a pine treatment for many years. The arsenic in the timber deters the termites, but as a famous poison, it has also attracted controversy. While our food and drink already contain a certain amount of naturally-occurring arsenic, which will not do us any harm, nobody wants to consume any more than they have to.
In 2003, the Australian Pesticides and Veterinary Medicines Authority (APVMA), the government authority responsible for the regulation of pesticides up to the point of sale, reviewed the use of CCA in pine and whether or not arsenic could leach from treated timber.
They concluded that while the use of CCA-treated pine was acceptable in some situations, such as structural, fencing and power/telegraph poles, problems might arise around children and CCA-treated wood. Children are more prone to hand-to-mouth contact than adults, and a very small child might even chew on a piece of wood. As a result, the APVMA restricted the use of CCA-treated timber where close contact with children and people occurred, so for example CCA-treated timber is now banned for use in garden furniture, children’s play equipment, domestic decking and handrails.
Using treated timber around vegetable gardens
With treated timber being a popular way to create a raised vegetable garden, the APVMA also looked into how much arsenic leaches into soil from CCA-treated timber. It concluded that the amount was variable, as was the amount of arsenic absorbed by plants, with no significant rises in arsenic levels in plants around CCA-treated posts (a certain level of arsenic occurs naturally in soil). Nonetheless, the APVMA does suggest a possible precaution of putting a plastic liner between the treated timber and the soil.
Alternatives to CCA-treated pine
The most popular alternative to CCA is a product called ACQ (Alkaline Copper Quaternary) treated pine. ACQ-treated pine is considered safe and effective, and should last as long as CCA-treated pine – with no arsenic.
LOSP (Light Organic Solvent Protection) treated pine is another alternative, but it is a less effective one with a shorter life span. Painting can help extend its life, and must be carried out with most LOSP products to maintain their warranty, but it LOSP-treated pine still doesn’t last as long as CCA- or ACQ-treated pine.
Another alternative is Eco Wood, which is used by National Parks – or if it’s appropriate for your application, you could choose to use as hardwood which is naturally more resistant to decay than pine.
Ratings for treated pine
An “H” rating on treated pine shows the recommended uses for that particular piece of wood, including its resistance to rot or insect attack.
H1 means that the pine is only suitable for use indoors, above ground, such as for internal joinery or furniture. H1 pine is not resistant to termites.
H2 pine is for use indoors above ground, in the same way as H1 pine, but it is resistant to termites.
H3 pine products can be used outside exposed to the weather, but not in contact with the ground. H3 is often used for decks, fence rails and pergolas. It’s resistant to rot and termites/borers.
H4 pine can be used in contact with the ground, or in the ground. This makes is suitable for fence posts and landscaping uses. It’s resistant to rot and termites/borers.
H5 is the pine you need for in-ground use and in contact with water. H5 pine can be used as structural support, for example, in retaining walls. It’s resistant to rot and termites/borers.
H6 pine is designed for use in salt water, for example for jetties, landings and boat hulls.
Tips for working with CCA-treated pine
- CCA-treated timber is not suitable for use around fishponds, aviaries, birdcages and beehives
- Take precautions – for example, wear gloves to avoid splinters, wear a mask when cutting, wear eye protection and do not get sawdust near food or food preparation areas
- Wash clothes that have accumulated treated wood sawdust separately
- Never burn any left over CCA-treated pine
- All CCA-treated timber now has to be branded as such until its first use