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Timber in Gardens

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Timber is the perfect material for garden edging, as it looks natural and lasts a long time. There has been some worry in recent years about using timber that has been treated with CCA (chromated copper arsenate).
The good news…

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Timber is the perfect material for garden edging, as it looks natural and lasts a long time. There has been some worry in recent years about using timber that has been treated with CCA (chromated copper arsenate).

The good news is studies have shown plants do not absorb chemicals from CCA products, so you can grow and eat your backyard fruit and vegies without concern.

What is treated timber?

Treated pine timber is wood that has been treated with a preservative to protect it from being destroyed by exposure to the outdoors.

Why treat timber with chemicals?

The purpose of treating timber with preservatives is to extend the life of timber products where untreated timber is not suitable. This makes the timber highly resistant to decay and insect attack, making it great for outdoor use.

Timber enhances the natural beauty of the outdoors. Here’s how to use treated timber.

Where is treated timber used?

Treated timber is used largely in garden and landscaping situations. In residential houses it is used for timber decking, retaining walls, pergolas, carports, bridges, playgrounds, boardwalks, cladding, treated pine sleepers, fencing and garden beds.

How long will treated timber last?

Used correctly in your garden treated timber will be a lifetime investment. CCA offers a lifetime guarantee against decay, which is equal to 40 years.

CSIRO

A number of studies have shown that CCA is not absorbed into above-ground food crops. Any possible concern can be eliminated by growing vegetables more than 100mm from treated timber garden edgings, or by lining the edgings with thick plastic. This has the additional useful effect of reducing soil contact with the wood, which also extends the wood’s life.

Using timber outdoors

As timber used in the garden is in constant contact with the ground it must be able to withstand damp and insect attack. Softwoods that have been treated to withstand these problems and durable hardwoods are both suitable for use in the garden but treated softwoods are easier to work with. Treated timber is given a rating of between h5 and H6, according to their exposure level.

Safety
  • Always wear gloves when handling treated timber and a dust mask when sawing it.
  • Wash sawdust off skin and hands
  • Only use treated timber that is dry and free of surface residues
  • Never burn any offcuts as the smoke and ash are also toxic
  • Don’t use around animals that may gnaw on wood. h5 is the least durable and the least hazardous. As the number increases so does the durability and hazard level. H6 timber is suited to situations where it will be permanently submerged. h5 or h5 are the grades commonly used in the garden. You will see this rating branded on the timber when you buy it.

(By Jecca Blake)

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