Treated Wood Works Outdoors

From time-to-time stories emerge, often driven by other agendas, that treated posts cannot be relied on. Gordon Ewbank, CEO, Wood Protection Association (WPA) reveals that the weight of scientific evidence and the experience of its members proves otherwise.

Treated wood is the mainstay material of the fencing industry and preservative systems do work when applied in accordance with industry standards and when treated posts are installed correctly. WPA members produce millions of treated posts every year and, contrary to allegations that failures are widespread, they report that incidents of early onset decay are now relatively uncommon. That’s because treaters have invested heavily to underpin confidence in treated wood for ground contact use. These investments include:

• Enhanced timber drying facilities • The introduction of incising technology to improve preservative penetration • Innovations in treatment plant design and process control • Improved communications to raise awareness about how to specify treated wood correctly • Offering third-party quality verification that treatment complies with either 15 or 30 years desired service life requirements in industry Standards.

Wood preservation is an industry of continuous development where treatment Standards are based on scientific evidence accumulated from years of laboratory and field testing, constant process innovation and extensive sampling and analysis of treated products. All too often though, if a post decays prematurely, the finger of blame points at the preservative. This is wrong. Claims that current preservatives lack efficacy totally ignore the evidence that they do perform.

Confirmation of Preservative Efficacy

It takes years of research and testing to develop an industrial wood preservative. Before a manufacture can sell any preservative to UK wood treaters they are required, by law, to get approval from the Health & Safety Executive (HSE). A key part of the HSE’s assessment process is close scrutiny of a preservative’s efficacy data and field test results. Approval for sale will not be granted unless sufficient evidence of effective performance has been accepted.

Confidence in the efficacy of current preservatives is further reinforced by early results from the 15- year independent UK field trial of 1,560 square sawn fence posts managed by BRE. After five years in the ground no significant signs of deterioration in treated spruce, pine, larch and Douglas fir posts could be detected yet the untreated control posts have already starting to fail.

In all markets, there is a choice of products and price points. The fence post market is no exception. Premium products with a quality assured pedigree and predicted performance do cost more. If a low-priced fence post is accompanied with a vague description such as ‘green treated’ then buyer beware! The level of preservative protection could be quite inadequate for the end use making premature failure almost inevitable.

The WPA Benchmark TM Scheme

Currently, some fencing contractors are calling for no-strings performance warranties on treated posts including consequential costs it fails prematurely. However, such calls swim against the tide of industry opinion now TTF members have adopted third-party certification as the best way to verify treated wood quality. Certification schemes are highly successful in other treated wood markets like USA, Canada and Scandinavia and TTF members believe the time has come to use them in the UK too. The QA scheme TTF members are most likely to turn to is the WPA Benchmark TM .

The WPA Benchmark TM for wood impregnated with preservative has been operating successfully for over 8 years and has accredited treaters in the UK and the EU. The scheme verifies, under third-party audit, that the treatment process and treated product are compliant with industry standards. Whilst the British Standard BS 8417 defines preservative penetration and retention levels by application ‘use class’ it does not set down how these critical requirements are achieved but points to the recommendations in the WPA Industrial Wood Preservation Code of Practice.

An Open Invitation

WPA is delighted that several major timber trade associations are collaborating closely in its campaign to promote quality and help grow the UK market for treated wood. The offer of collaboration is always open to those who share our mission to make the most of wood as a sustainable, low environmental impact construction and landscaping material.

The WPA Industrial Wood Preservation Code of Practice is available as a free download from � www.thewpa.org.uk