Timber preservation is the process where chemicals are added to the timber to protect it against weathering conditions and wood-destroying organisms. It has been implemented for as long as the wood has been used for building purposes. One of the first attempts made to protect timber with timber preservation chemicals was by rubbing or brushing the chemicals into the timber. – Wikipedia

Soon enough new techniques were developed and to this day, the best method used is to impregnate the chemicals into the timber by using high pressure.

In our fast-growing, modern world we need quality timber that is economical and always readily available while still practicing forest sustainability. For instance, forest plantations can offer the same value of timber in a shorter time period, thereby providing a positive impact on the economy and natural forests can be preserved. In South Africa, the largest plantation areas are in the provinces of Mpumalanga, KwaZulu-Natal and the Eastern Cape where eucalyptus (gum) and pines are mostly grown. This wood is not durable but when treated, it can last a lifetime.

Implications of using untreated timber that is not properly treated with preservatives

In South Africa, many injuries and major economic losses occur because untreated timber is used in environments where timber is exposed to hazardous conditions or the preservatives used on the timber is applied incorrectly making it ineffective to withstand certain hazardous conditions. E.g., Repairing damaged structures can end up being not only unsafe but more costly than it would’ve been to build the structure with the correct timber from the start.

Untreated timber deteriorates

Wood follows a deterioration process after it has reached its lifespan. For instance, weathering conditions and timber-destroying agencies cause wood to deteriorate in a considerably shorter amount of time. (Note: If timber is treated, it is protected against these elements thereby increasing its lifespan).

Below we will discuss in detail how this happens;

  • Weather and environmental conditions

Moist is almost the biggest enemy of wood – when the wood is moist for a considerable time, it allows the growth of staining fungi and mould fungi. Wet wood is a breeding ground for wood-eating insects.

Furthermore, exposure to the sun will damage its surface causing cracks and possible warping throughout Over time the UV light begins depleting oils from the wood.

Unstable wood house.
Unstable Wood House
  • Wood eating insects

Wet wood is basically a breeding ground for insects. Wood-eating insects feed on the wood tissue and make holes in the wood cells to live in. Some insects are:

  • European house borer (Hylotrupes Bajulus)
  • Powder post beetle (Lyctus brunneus)
  • West-Indian dry wood termite (Cryptotermes brevis)
  • Subterranean Termites (family Termitidae and Rhinotermitidae)
  • Xylocopa spp (Carpenter bees)                                                                                 – Info extracted from SAWPA
Powder post beatle.
Powder post beetle
  • Fungi

Fungi is the cause of dry rot in timber. The fungus grows by consuming wood fibre, and the wood becomes soft. Fungi attack the cell walls of wood tissue for their own food and destroy it. According to the TheBeamGuy, there are two kinds of rot caused by fungi namely:

Brown Rot – the wood cracks and forms what looks like cubes. The colour of the wood turns slightly darker. They are generally very visible and distinct especially when the wood is dry.

White Rot – The wood has more of a fibrous-like appearance and it turns slightly lighter in colour.

What rotten timber looks like.
Rotten Wood

Risks of using untreated timber in structures

As mentioned above, untreated timber (wood that contains timber preservation) is exposed to wood-destroying elements such as wood-destroying organisms and weathering elements. Should you decide to build your structures with untreated wood where it will be exposed to these destroying elements, you will definitely have some risks:

Safety Risk

As timber deteriorates, the structures weaken and the chances of it collapsing are greater. They eventually become too weak to safely support the building and contents. These structures are also more vulnerable to weather conditions such as heavy rains, storms and strong winds. This is a huge safety risk as anyone could easily get hurt if the structure collapses while they are caught inside.

Health Risk

Mould grows well on wood where there is moisture. Exposure to damp and mouldy environments may cause a variety of health effects.

According to CDC (Centers for Disease and Prevention); “Exposure to moulds can lead to symptoms such as stuffy nose, wheezing, and red or itchy eyes, or skin. Some people, such as those with allergies to moulds or with asthma, may have more intense reactions. Severe reactions may occur among workers exposed to large amounts of moulds in occupational settings, such as farmers working in mouldy sheds. Severe reactions may include fever and shortness of breath.”

Fire Risk

A fire can go from a simple spark to a blaze in a matter of minutes. Generally wood catches fire quite easily. If the wood of your structure is untreated, your structure runs a high risk of burning out completely in a short amount of time and your ability to escape the fire becomes significantly less.

Treated wood slightly insulates the wood and slows fire growth giving time to escape. Timber that is varnished with fire retardants also has less chance of causing severe damage.

Timber preservation and the law

When timber is treated with preservatives, certain standards are put in place. These standards (SANS – South African National Standards) are set according to national levels of preservative treatments for a classified range of hazard conditions and to promote and extend the use of timber and to conserve raw materials.

All treated timber should be marked according to their hazard classes and have the SABS stamp of approval. SABS (South African Bureau of Standards) sets the standard at which treated timber needs to be treated and handled. Products with the SABS seal of approval have been checked and found to be compliant with South African laws. This means that your products are going to be of high quality and that the manufacturers have done their due diligence. 

Timber preservation qualities

If timber is treated properly, it is protected against all wood-destroying elements and its lifespan is extended to at least 20 years. It should have the following qualities:

  • Availability and affordability from a reputable supplier.
  • It should not contain any harmful substances, gases etc.
  • Sealants, paint or varnish can be used on the treated timber for decorative purposes
  • The strength of timber is not affected by the preservative.
  • It does not contain any unpleasant smell.
  • It does not get affected by any weathering conditions
  • It does not get affected by fungi; insects, etc. and should also be efficient to kill them.
  • It does not corrode metals when it makes contact with them.
  • The preservative used in the treatment does not leach out.
  • It is not harmful to the environment.
  • It is procured from a sustainable forest.

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