Although there are several alternatives on the market, preservative treated softwood is undoubtedly the most economical fencing material – particularly for agricultural applications. Timber is strong yet lightweight, easily worked and can be adapted quickly to suit on-site changes or repairs. Today it is even more relevant as it’s one of the few building materials that can help us meet carbon zero goals due to its environmental credentials.

Treated softwood fencing and construction components – typically Pine and Spruce, have been through a factory controlled, industrial treatment process. This results in the timber having
an effective barrier of protection against decay and insect attack. The penetration and retention of wood preservatives are defined in British Standards and are aligned to their end use through the Use Class system. Such added durability extends the service life of the timber and allows plentiful, fast grown species to be used in areas that wouldn’t ordinarily be practical.

Re-working treated timber

Timber components are treated in their finished, machined form. Because of this, treated products are designed to be installed without re-working where possible. This may seem impractical – but by cross- cutting the timber you are exposing an untreated core, thereby breaking the ‘envelope’ of preservative protection. However, there is an easy solution when components need to be re-worked – especially as we’ve just highlighted the fact that timber can be adapted on-site.

Cut End brush-on treatment

By giving each cut end, two liberal brush coats of a suitable end grain wood preservative, you can maintain the integrity of the treatment. This also applies to areas which have been bored, drilled or notched – for example to accept fixings.

Your timber supplier should be able to recommend a suitable product to use – which may well originate from the manufacturer of the preservative used in the treatment. Several of our members supply such treatments. If you need to source a cut-end product, please get in touch with the Wood Protection Association (WPA).

Post installation

It’s important to remember that preservative penetration achieved by brush application is less than that achieved by the industrial treatment process.
So even if an end grain product has been applied to a cross-cut end of a treated post, this end must NEVER be embedded in the ground. Instead put the un-cut end in the ground.

Mechanical incising of the surface is now widely used to help achieve desired preservative penetration levels. Some fence posts only have incising along part of their length and, in such circumstances, the un-cut, incised end of the post must be placed in the ground.

  • Try and source treated posts and rails to the finished sizes you require.
  • Make sure posts are treated to Use Class 4 levels of protection – for complete assurance, make sure they’re WPA Benchmark accredited.
  • If a post does needs shortening, then cut the top (at an angle to shed water) and apply two coats of brush- on preservative and fit the cut top with a post cap to reduce water penetration into the end grain.
  • If you require extra protection at the groundline, specially designed ‘wraps’ for treated timber posts can be used to provide an additional barrier against moisture – ask about product guarantees.

    Specification and WPA Approved Treaters
    By correctly specifying and installing treated timber you can be assured it will perform in the field. To source independently audited timber treaters you can trust, check out our list of WPA Benchmark Approved Treaters on our website or get in touch.

    For more information on wood protection technologies visit www.thewpa.org.uk or email contact@thewpa.org.uk

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