Fencing
Image courtesy of Woodbank Timber Ltd
Image courtesy of AV Birch & Koppers Performance Chemicals
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LIFE DOESN’ T GET MUCH tougher for a piece of timber than being a fence post on the farm: stuck in damp or boggy ground, out in all weathers from baking hot to freezing cold, surrounded by livestock and exposed to the elements and decay organisms both above ground and below ground. So anything that can protect timber from insect and fungi attack in that extreme environment over long periods has to be special.
Industrially-applied high pressure preservative treatments for fencing timbers have been around for years. The controlled treatments force the preservative system deep into the timber structure providing effective long term protection against the threat of rot and extending the service life of the timber components.
Need Agricultural Fencing Timbers? Look for Quality Suppliers
These treatments can be varied to suit the eventual end use of the timbers. The highest general classification of treatment is for timbers permanently in ground contact, such as agricultural fence posts and strainers. This level of treatment is referred to in the timber industry as Use Class 4 from European Standard EN 335. The first question any farmer should ask when buying preservative-treated posts or strainers, therefore, is have they been treated to Use Class 4 requirements? If so you should be looking for a service life of 10-15 years with some suppliers even offering premium performance timbers with 20 or 25 years’ expectations.
The production and supply of preservative-treated fencing timbers is through timber companies and merchants and sawmills. But whoever the supplier, achieving a quality preservative treatment for fencing timbers depends on four main key elements: what species of timber is being treated; how well the timber is prepared prior to treatment; how effective the wood preservative is and how professional is the treatment process?
TIMBER SPECIES All timber species have their own characteristics with some more suitable for certain end uses and some easier to preservative-treat than others. For the fencing and agricultural markets, the main species used are Spruce, Pine, Larch and Douglas Fir, because of their abundance and availability. All these species are usually sourced from recognised, sustainable resources.
All of these species can be given an effective preservative pre-treatment for both in and out of ground contact applications to provide an effective extended service life against the threat of decay and insect attack.
BS8417, the Code of Practice for the wood preservation industry, now focuses on preservative penetration results into the timbers and, for the treatment of Spruce ground contact timbers in particular, there is a minimum requirement of 6mm preservative penetration into the sapwood zone of the timber component. Some companies are now using surface incising techniques to help achieve these penetration requirements.
Ask your supplier about the species they use and check whether the treatments meet the requirements of BS8417.
TIMBER PREPARATION
All harvested timbers have a moisture content – that is, a measurable level of water within the wood. This moisture content should be at a specific level to allow the wood preservative to penetrate sufficiently during the pressurised treatment process. Freshly harvested timbers,
26 Jun / Jul 2016 www. farmers-mart. co. uk