Raising the bar on treated wood quality

WPA Benchmark is raising the bar on outdoor wood quality

-       three part strategy to build confidence in treated wood performance

-       first UK treater awarded WPA Benchmark on 30 yrs posts

If there is one question that characterises the UK market for fencing, decking and ground contact wood it’s service life performance. Just how long will treated wood last? No product will flourish if buyers lack confidence in its performance so the Wood Protection Association (WPA), the UK technical and advisory organisation on timber pre-treatment, has invested in a number of strategic initiatives to help industry raise the bar on treatment quality and performance. The WPA strategy has three key interconnected elements:

1) a quality assurance scheme for treated wood;

2) an approval scheme for preservatives that establishes the preservative retention required to protect timber in ground contact and

3) establishing a long term field trial of softwood deck and fence posts to assess durability performance.

WPA director, Steve Young says that building market confidence in treated wood performance is right at the top of the WPA’s agenda: “ When the reputation of any product is called into question, strong and credible reassurance is essential if the market is to retain confidence in that product - the WPA is committed to providing timber treaters with the tools they need to provide that reassurance about treated wood.”

 Spruce, pine, Douglas fir and larch are the dominant softwoods for outdoor wood applications in the UK. Each species has its own natural qualities that affect how the durability performance conferred by preservative treatment is achieved. For example, the biological structure of spruce makes it more difficult to treat whereas pine is more readily penetrated. Service life performance of treated softwoods, particularly in ground contact BS8417 use class 4 applications, is determined by the characteristics of a species, its conditioning prior to treatment as well as the preservative solution strength and the process pressure cycles used to achieve the penetration and retention necessary for any given end use. This combination of factors is known technically in wood preservation speak as the ‘safe relationship’. Getting the safe relationship right is essential to ensure treated wood is fit for purpose outdoors and will meet the requirements of the 15 years default desired service life specification in BS8417.

 WPA Benchmark gets to the heart of treated wood quality

Making sure the safe relationship is correctly established, monitored and formally verified by an expert third-party lies at the heart of the WPA quality scheme for treated. Known as the WPA Benchmark, the scheme was developed in consultation with representatives from timber treaters, the WPA and BRE. It provides a credible way for treaters to rebuild buyer confidence in both the quality of the wood treating process and the ability of a specific component such as a deck or fence post to perform for the minimum 15 years required in British Standards.  The safe relationship is specific to an individual treatment plant and requires extensive analytical work to establish in collaboration with the preservative supplier. It is time consuming work but necessary to achieve the quality consistency required to satisfy customers.

First 30 years certificated products – a significant milestone   

Those treaters who have embraced the WPA Benchmark scheme are very enthusiastic about its benefit to their business by improving their in-house expertise and control of treated wood quality and raising customer satisfaction levels. A number of treaters producing wood to the WPA Benchmark quality standard are now homing in on achieving WPA verification of the production of components to meet the BS8417 30 years desired service life specification. Several treaters are now on the verge of this distinction and the first certificate has already been issued. Bond Timber was awarded WPA Benchmark certification for round pine posts meeting the 30 years specification on 8 March - a significant milestone in the progress of the WPA Benchmark scheme. Commenting on this achievement Steve Young says:

“ Bond Timber has built its business on putting quality treated wood and customer satisfaction first. They have worked hard to get 30 years material included within the scope of their Benchmark certificated products and I am sure other treaters in the WPA Benchmark quality scheme will be hot on their heels to get more 30 year products certificated soon. We are certain customers will welcome the initiative that Bond and other like minded treaters are taking.”

Getting the preservative retention right

The WPA’s approval scheme establishes the minimum retention of a copper/organic biocide preservative necessary to deliver either the 15 or 30 desired service life in BS8417.   This scheme is specifically for wood preservatives used for species in direct ground of freshwater contact. It is part and parcel of the WPA Benchmark strategy and brings the UK treatment industry closely in line with the quality schemes of other major treated wood using countries.  Although preservative manufactures participate voluntarily in this scheme, Steve Young says it is very pleasing to see that all the major preservative suppliers have submitted product data for scrutiny by the WPA’s independent panel of experts. He said:“ The support of the major preservative suppliers in helping to establish and promote WPA initiatives is vital if industry is to succeed in building market confidence and grow demand for quality treated wood.”

Field trial of long-term durability performance established

Last year the biggest field trial of commercial softwood posts treated with a WPA approved preservative was established. The field trial is being managed for WPA by BRE and includes two sites with differing soil conditions, one in Scotland and one in England. In all the trial comprises 1400 75 x 75mm treated sawn spruce, pine, Douglas fir and larch posts, 600 of which have been mechanically incised, and 160 untreated controls, across both sites. The preservatives, loadings and treatment processes used are in accordance with WPA standards and independently audited by BRE.The trial will run for 15 years and provide the data essential to informing improvement in treatment quality and British Standards.

 Quality failure opens the door wider to man-made materials

There will always be several sectors with different price points in any market and the decking, landscaping and fencing market is no different. The price of a component will almost always have a direct relationship to its quality. And often the buyer/user has no means of knowing if the product they are about to buy can be expected to meet their service life expectations. The WPA Benchmark scheme, preservative approval scheme and field trial is providing UK timber treaters with a credible and commercially relevant platform on which to raise treatment quality and customer satisfaction ratings. If the momentum started by the early adoption and support for these initiatives can be maintained then the long-term prospects for growth in demand for treated wood for ground contact applications are good. There is no room for complacency though; there is a real and present threat to the use of treated wood for ground contact applications from man-made materials which makes the need for an effective and consistent industry wide response to performance all the more vital.  

The WPA remains totally committed to helping wood treaters meet this objective.


To find out more about what’s involved in joining the WPA Benchmark scheme and the benefits it can bring contact:

Steve Young on steve@wood-protection.org



Steve Young


Wood Protection Association

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Posted at 3:15 pm on March 23rd, 2016