">Timber Treatment Information - Softwoods

Timber treatment information


Most of the timber we sell at Softwoods has been treated in one way or another. While the chemicals used for treatment change, the treatment process is always very similar.

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The first step in the process is obviously the logging of the timber. All of our timber is Plantation grown. Once the timber has been logged it is cut into workable sizes in the mill.

If left untreated, pine placed inground will rot within 12 months, however treated pine will last up to 30 years. Prior to treatment the timber is kiln dried to remove moisture and allow for better absorption of the treatment solution. Timber is dried to 15% of it’s original moisture content before the treatment begins.

Once the timber has been suitably dried it is subjected to a vacuum to extract as much air as possible. Once this is done the preservative is pumped into the vacuum and pressure is applied until the appropriate uptake of solution has occurred.

When the appropriate level of preservative has been absorbed the solution is pumped from the tank and the vacuum is reapplied to extract any excess solution.

As soon as the treatment process is complete the timber is again kiln dried to return its moisture content to 15%. As the process is now complete the timber is then packed and shipped.

Dressed treated pine (DAR)

Most of the timber used in pergolas and decking substructure is CCA DAR treated pine. CCA treated timber is pressure treated and designed for use in outdoor areas or areas of increased moisture or insect habitation.

DAR indicates that the timber is dressed all round, which means simply that it has been planed smooth on all surfaces.

CCA stands for Copper (23-25%) Chrome (38-45%) and Arsenic (30-37%). This solution is water borne and is designed to protect timber from rotting, attacks from fungus, termites and other wood boring insects.

Within the solution Copper acts as a guard against rotting and decay, Arsenic is used as a pesticide to ward off insects and Chromium is used to bind these two agents together and make the treatment insoluble, in doing so preventing the solution from leaching from the timber.

Once treated with a CCA solution pine will have a slight greenish tinge. CCA treatment will guard against decay and insects, however natural discolouration will still occur if the timber is left unpainted or unstained.

Treated timber is available in several different finishes to suit different needs. The “finish” of the timber is the appearance of the surface of the product.The most common finish for treated pine is micro-reeded or rougher headed. This is a machined finish with a finely bevelled appearance on the surface of the timber. This finish helps to smooth the appearance of any knots or imperfections in the timber and it allows for ease of painting.

CCA Safety

In accordance with an APVMA (Australian Pesticides and Veterinary Medicines Authority) recommendation of March 2005, CCA treated timber will no longer be used in the production of:

  • Garden furniture
  • Picnic tables
  • Exterior seating
  • Children’s play equipment
  • Decking boards
  • Handrails

Since CCA treated pine has been phased out for use in areas where children could come into frequent direct contact with the timber – we no longer stock any CCA decking and sell only LOSP treated handrails. We only use CCA timber for purposes that are safe and fully government approved.

LOSP treated pine

The other main form of timber treatment is known as LOSP or Light Organic Solvent Preservative. LOSP is a treatment that is usually a white spirit based solvent which contains copper naphthenates and synthetic pyrethroids as well as other chemicals to provide protection from insects and decay.

LOSP treated pine is usually machined to the required lengths and shapes before the treatment is applied. As a result of this less pressure is used in the treatment process and a little less penetration of solution is achieved. This does not affect the longevity of the timber, however it means that LOSP timber must not go in ground and if the timber is cut the cut ends must be resealed with a suitable sealant.

LOSP timber is frequently coated with a protective oil based primer which is usually pink. This primer is applied to stabilise and protect timber during storage and installation, not as a paint primer. As a result it is recommended that LOSP primed timber be sanded down to remove the primer before painting.

Unprimed LOSP timber is natural in its appearance as the solution used is clear and hence causes no discolouration of the timber. Like CCA the timber will weather and discolour if not stained or painted.

LOSP treated timber is occasionally treated with an oil based protective primer. This is called a Pink Primed (as the primer is usually pink) and it is always applied on kiln dried DAR finished LOSP. The Primer is intended as a protective coating only and should be sanded down before painting of the timber.

Alternative treatments

A few other treatments are currently available, they are both water based solutions and are quite similar to CCA in their potential uses. They are called ACQ and Tanalith E (or copper Azole)

ACQ or Alkaline Copper Quartenary is a relatively new treatment which is a water based solution which uses Copper to protect against rot and fungal attack and Ammonium Quartenary as a pesticide. ACQ treated timber possesses most of the same qualities as CCA timber in that it can be used in inground applications.

Tanalith E or Copper Azole treatment is another new water borne solution which again uses Copper as a fungicide and Azole as a pesticide, it too can be used in inground applications and has most of the same properties as CCA treated timber.

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