Timber fences can last from a few short years, to in excess of fifty years, depending on their construction, treatment and the choice of materials.
During their lifetime, timber fences have to withstand the ravages of weather and attack by insects and fungus, so it is important to select appropriate materials for their construction. When selecting timber, you should also consider your own level of experience and the tools you have. Softwoods, such as preservative-treated pines, are easier to work with than hardwoods.

The majority of decorative fences are made using treated pine. Treated pine timber should have an H4 rating for the posts, and an H3 rating for the rails. If you use hardwood, select a timber with a very durable rating for posts and a durable rating for rails. Consult your local timber or fencing supplier for advice.

Covering boards
These may take the form of pickets, palings, slats, boards or louvres and should not come in contact with the ground. As a result, they can be constructed from moderately durable hardwoods, or from a preservative-treated pine with an H3 rating. The durability rating of hardwoods and the hazard level of preservative treated softwoods can be obtained from your local timber merchant.

Posts
As fence posts are in contact with the ground, they are prone to attack by insects, fungus and moisture.

Fixing materials
Like the timber, the materials to fix the timber together will be exposed to the elements - to the sun, rain and damp. Nails should be hot-dipped galvanised to ensure maximum resistance to corrosion and also to reduce marking of the timber from rust stains. Ordinary steel nails may corrode when in contact with CCA timber products. Bolts, nuts, washers, coach screws or any other fixing device should also be hot-dipped galvanised to maximise the longevity of the fence.
cost you extra.

Ordering timber
Usually timber merchants carry timber with a minimum length of 1.8m, and then in lengths increasing by 0.3m (consider this when ordering posts and rails). Palings and pickets usually come in set lengths, so check the length you require. If you want to have the timber cut to size, it may cost you extra.

Timber can be ordered as rough sawn or dressed all round (DAR). Timber that is DAR has had all four surfaces machine planed to a smooth finish. This reduces the finished size of the timber but makes it easier to paint or stain.it may Therefore, choose the most durable hardwood timbers or preservative-treated pine with an H4 rating.

Preservative-treated timber
Softwood of low durability, usually radiata pine, can be treated with chemicals to transform it into a product of higher durability, resistant to attack by fungi, borers and termites. These preservative-treated softwoods are rated according to a hazard level system ranging from H1 to H6, with H1 being the least durable (and the least hazardous). This rating is branded on the timber. As rails are not in contact with the ground, they can be selected from any durable hardwoods or from preservative-treated pine with an H3 rating.

The timber is treated with compounds of copper, chromium and arsenic, termed CCA. When using this material:

• wear gloves and dust masks when sawing.
• any cut or sawn surface of this material will need resealing to ensure its effectiveness in resisting attack.
• dispose of any offcuts by burying them. Don't burn them as the smoke and ash is toxic.

Tip: To ensure your fence lasts for many years, keep the timber protected with a solid coat of paint and use preservative-treated timber to reduce the chance of attack by insects and mould.

Source: Fences (Murdoch Books) (out of print)