Building With Timber

Timber is one of man’s oldest building materials. Few of any of its competitors can match it for versatility, beauty, cost effectiveness and positive environmental credentials.

Easy to work, light but strong, available in a wide range of species sizes and finishes, timber is an excellent insulator and uses less energy in its production than any other building material. It can be finished in a number of different ways, adding both warmth and character to a whole variety of environments.

Timber Preservation

Advances in timber preservation are extending the use of readily available and renewable species into a wide range of applications where durability is required.

Preservation gives timber durability – from attack by insects and decay producing organisms.

Technology is improving these qualities even further. Preserving chemicals are being better applied; they are safer to handle and the range of preservative-treated wood is now extensive.

Advantages of Treated Timber

• It provides long life under hazardous conditions.
• It is cost efficient.
• It is versatile – can be used outdoors, indoors, above ground, underground, and in direct contact with fresh or salt water.
• A variety of finishes provide additional attractiveness.
• It provides flexibility for design and can economically overcome difficult site situations.

Main Types of Preservatives

• Creosote and modified creosote-based preservatives, e.g. Tanalised K.
• Light organic solvent based preservatives, e.g. Protim, Tanalised Azure, Timtech Az.
• Copper chrome arsenic preservatives (fixed waterborne preservatives) e.g. Tanalised C, Tanalised E, Lifewood, Naturewood, Timtech CX, Timtech Q.
• Preservative compounds of boron or fluoride e.g. Polybor, Tanalised B, Timtech BG, Osmose Liquid Boron, Sodium Fluoride.

Types of Treatment

Vacuum / Pressure Impregnation:
e.g. CCA or modified creosote –
Is used to achieve deep protection for piles, poles, fencing, building timbers and many types of wood used in domestic and industrial construction.

Double Vacuum / Immersion:
e.g. LOSP –
Is used for the protection of building timbers not in ground contact, e.g. cladding, decking and fabricated joinery components.

Dip / Spray:
e.g. Polybor –
These preservatives are designed to protect timber against insect attack and should be used for indoor or sheltered situations above ground. They are popular treatments for softwood house framing.

Levels of Preservative Treatment

Most pressure-treated timber is preserved for specified end uses. For example, timber treated with CCA or LOSP for cladding, or other above-ground use is not suitable for use directly in the ground. Your supplier should be aware of these and related facts and will be able to advise you on your special needs.

Where to Use Treated Timber

Virtually anywhere timber is exposed to weather, in contact with the ground or under water.

• Framing and roofing timbers.
• Timber decking, pool surrounds.
• Wall linings, cladding, fascia.
• Poles and posts, haysheds.
• Stumps, sub-floor timbers.
• Fencing, landscaping, playgrounds.
• Bridges, railings, marinas, piers.
• Oyster farms, vineyards.
• Railway sleepers and wagons, truck floors.
• Water cooling towers in power stations.
• Pergolas.
• Domestic fencing.
• Rural fencing.
• Boats.

Creosote, modified creosote, and other oil-type preservatives are most suited for heavy duty exterior work, such as railway sleepers, bridge decking, transmission poles, marine piles and fencing.

Fixed water-borne preservatives, which will not leach out even when in contact with running water, are most suitable for domestic buildings, posts, poles, landscaping fencing, cooling towers, decking, cladding, etc.

Light organic solvent preservatives are designed for timbers not in contact with the ground. They should be used for factory assembled joinery, e.g. window frames, and for building at home, e.g. elevated decking, pergolas and fascias. They are also used to provide protection for garden furniture.

You may like the effect of natural weathering, but for the best performance, including long service life, your timber should be treated with a water repellent stain.

Treated timber can be painted or stained just like untreated timber. If paint or stain is not used for the final finish, protection with a water repellent is recommended for best results.

Standards for Treated Timber

It is a requirement of the TPAA that members treat to comply with the requirements of Australian Standards and State legislation. The main timber preservation standard is:

AS 1604 – 2006 series. Specification for preservative treatment  (5 parts)

Health and Safety

In normal conditions, the use of treated timbers presents no hazards to people or animals or the environment.

It is recommended that normal precautions are observed during construction, that garden gloves be worn during assembly and that when cutting or sanding timbers a simple mask be used to prevent inhalation of dust. Off-cuts and waste material must not be burnt in confined spaces or in barbeques. Small quantities of treated timber wastes may be disposed of with household garbage. Larger (industrial) quantities should be disposed of at appropriate landfill sites.

Additional information is available from the TPAA.

What is the TPAA?

The Timber Preservers’ Association of Australia is an organisation comprising timber treaters, suppliers of preservatives, research organizations and individuals, and any other individuals or organisations having an interest in the use of preservative treated timber.

The TPAA promotes a knowledge of the principles and methods of timber preservation within the industry, assists in the establishment of and adherence to standard specifications for preservative treatment of timber, and promotes the maintenance of high standards of practice in all sectors of the preservation industry.