Tried and tested treated timber
PERFORMANCE IS everything around the farm. Would you think of investing in new machinery without making sure it was up to the job? Are crop protection products allowed to be used without being field tested and proved? The very same approach applies to preservative treated timber – such a versatile material for agricultural uses.
Preservative pressure treatments will significantly extend the service life of timber by providing an effective protection against all forms of wood decay and insect attack. Since 2003, ‘new generation’ products have been introduced by preservative suppliers to replace the traditional CCA (chromated copper arsenate) based formulations, which now have restricted use. But these ‘new generation’ products have very different performance credentials to each other, and farmers and agricultural merchants buying in treated timber need to know exactly what they are getting.
There are 4 main elements to be considered and asked of your treated timber supplier.
• What species of timber is being treated?
• How well is the timber prepared prior to treatment?
• How effective is the wood preservative?
• 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 agricultural and fencing markets in the UK the main species are Spruce, Pine, Larch and Douglas Fir, because of their abundance and availability.
All, with the correct preparation and treatment, can be given an effective preservative pre-treatment for both in and out of ground contact applications, to provide a minimum desired service life of up to 15 years against the threat of decay. A robust protection for stakes, posts, strainer posts and farm buildings.
Timber Preparation
All harvested timbers have a moisture content – a measurable level of water within the wood.
A key criterion for effective preservative treatment is that this moisture content should be
at a specific level to allow the wood preservative to penetrate sufficiently during the pressurised treatment within the industrial treatment vessel. Therefore, freshly harvested timbers have to be dried to reduce the initial moisture content. Also, if the timber is dried prior to treatment, it is much less likely to ‘split’ in service; ‘splits’ can give the potential for inner areas of the treated components to be attacked by wood destroying organisms.
The most effective and economical way of achieving this moisture content reduction is by natural air drying methods. Harvested timbers can be held in stock, both prior to and after machining, to allow the moisture content reduce to the required level, usually checked with a moisture meter.
Timber Preservative
All ‘new generation’ wood preservatives are different and have different performance credentials. Unlike some European countries, all that is needed to place a new timber preservative onto the market in the UK is to prove its performance through a series of laboratory tests. However, can this really be a true test, particularly when most agricultural treated timbers are used externally and in ground contact situations – the most extreme test for timber?
Tanalith E wood preservative is a unique formulation product from Arch Timber Protection, world leaders in timber protection. Unlike some other ‘new generation’ products, Tanalith E has been rigorously tested by Arch and independent authorities in field test sites around the world, all with differing climatic and potential decay threat conditions, to achieve the optimum protection for external, ground contact timbers.
Tanalith E has now been used successfully for over 10 years in the UK and even longer across mainland Europe. It is now the preferred preservative in over 30 countries around the world.
It is used by leading treatment companies in the UK to provide quality Tanalised E treated timbers that will perform as expected.
Treatment Process
The level of preservative treatment given to timber can be varied according to its eventual end use.
Within the treatment industry there are Use Classes, which define the typical end use of the timber and the appropriate level of preservative protection required. The main Use Classes range from I to IV. Timbers that require the minimum protection, for instance internal building timbers, where there is no chance of wetting, come under Use Class I. Agricultural timbers, which are permanently exposed to the weather and could be either used in or out of ground contact, require a higher degree of protection and are designated in Use Classes II-IV. It is imperative to check with your supplier what Use Class your treated timbers have been prepared to – especially those that are destined for Use Class IV permanent ground contact applications.
In the days of CCA wood preservatives, the quality of the treatments were measured by the treatment cycles, in terms of times and pressure and vacuum periods, with no particular measurement of the preservative penetration into the timber. For ‘new generation’ products, industry requirements are more focussed on penetration results. For instance, with the treatment of Spruce ground contact fencing timbers, there is a minimum requirement of 6mm preservative penetration into the sapwood of the timber component.
