“Making the most of Wood” was the theme for this year’s Wood Protection Association (WPA) Conference near Derby on April 6. The event was billed as the WPA’s most ambitious conference yet, with sessions on sustainability, construction and performance. A heightened focus on treatment issues in the timber trade gave the event added interest, with results being shared from the WPA & Timber Trade Federation’s joint survey of companies involved in the supply of treated of wood in the UK.
As WPA director Steve Young shared in April’s issue of TTJ – the big news following this survey was that the WPA was looking at re-shaping its strategy by looking at providing treaters who produce treated wood under the WPA Benchmark quality assurance scheme with the added benefit of ‘performance assurance’ – a de facto national warranty.
But it was sustainability that kicked off the sessions with BRE’s sustainable materials lead Ed Suttie giving the keynote address.
Mr Suttie said timber had a fantastic opportunity ahead of it due to its sustainability and lifecycle credentials. Issues such as ethical sourcing and low environmental impact have come to the fore at a time of increasing demand on resources, with the world’s population now pushing around 7.2bn people.
He also highlighted “beyond carbon” concepts which could benefit the timber/ forestry sector such as health & well-being and recreation.
He said one-sixth of the softwood supply goes into fencing and one quarter of all the softwood resource will flow into the preservative and treatment markets.
There was an evolution about service life going on, he added, and it was important to understand reliability, the natural variability of wood products, mechanical properties of wood and weathering.
He said good work being done in wood protection included using incising to get better reliability with timber treatment of Sikta spruce, while the WPA’s BenchMark QA scheme, national field trials and product approval schemes were important developments.
“People may not “get” our product but they might if you tell them this is a reliable product that will meet their required service life,” he added.
British Timber
Dougal Driver, CEO of Grown in Britain (GiB), said the organisation was seeking to reconnect the public to British woods and their products through GiB labelling, in a similar way to the agricultural sector’s red tractor mark.
“This is a really interesting time for us because people are talking about being British. It resonates hugely with people. “Brexit is clearly an opportunity. “Flying the flag is of the now and possibly for a long time ahead.”
GiB has a trademark licensing system for British wood products, with about 70 licence holders currently from across the UK, including Bond Timber and Arnold Laver. The target is 100 licence holders by the end of 2017.
“We are aware that British wood will not replace all imports but we can make more use of what we have and get into more supply chains.
“British wood is not suitable for everything but we need to overcome old perceptions of British timber’s strength, durability and applications.”
Mr Driver highlighted Vastern Timber’s Brimstone wood – thermally-modified UK hardwoods, which was “flying off the shelves”.
Future challenges existed due to insufficient tree planting levels, he added. The Scottish government has published plans to expand planting targets by 50%, but English planting targets are far less than in Europe.
The UK government has committed £19.2m to support the creation of new woodlands over 30ha.
Timber preconceptions
Ivor Davies, research fellow at Edinburgh Napier University, told delegates of the “huge potential” for more timber housing in the UK, sharing examples of UK timber construction. Mr Davies, who recently authored a report called Sustainable Construction Timber, predicted UK timber would be used for crosslaminated timber (CLT) construction on an increasing scale.
But it was important to deal with preconceptions about wood. He explained that there was no correlation between fast/slow tree growth rates and density.
“Slow-grown timber is usually not better than fast-grown timber.”
And he said Japanese larch was as durable as European larch.
“The preconception is usually down to the fact that Japanese larch is usually harvested earlier than European larch so has more juvenile wood.”
Meanwhile, the revised version of BS EN 350 gives oak a varied durability, which poses a challenge for industries using oak. “How do we pull that together into a simple suite of guidance for the oak industry?” “Most European oak can be durable but there is a big ‘but’ and we need to sharpen that statement up.”
During question time WPA technical director Gordon Ewbank described CLT as a “PR disaster waiting to happen”, saying the overseas manufacturers of the material did not want to treat the timber. However, he said there was a real opportunity for homegrown timber to be used in CLT construction. Steve Young also warned about the need to treat construction timber, raising the spectre of the 1983 World in Action television documentary, which damaged timber frame construction’s image. “That is going to happen with CLT unless we grasp this nettle.”
Research and development
Jöran Jermer, who leads the SP Technical Research Institute of Sweden (RISE) team involved in assessing the performance of treated wood, shared results of field trials at its Borås site.
Testing involved copper organics treatments, modified wood and naturally durable timber.
In an 11-year BS EN 252 ground contact proximity test acetylated wood (modified) came out best, followed by wood treated with linseed oil.
But fifty-day exposure tests saw treated wood retain its good looks, with modified wood and Scots pine looking unsightly.
“Preservative-treated wood came out best from this test,” said Mr Jermer In service trials with noise barriers and jetties saw all materials perform quite well with no big difference between treated wood and untreated wood due to the design of the noise barrier.
With the jetties testing, different materials including wood-plastic composites were tested, with the latter retaining its colour. Kebony turned grey after three years. “I really think it’s necessary to use field trials for the evaluation of new wood preservatives. They give the best information of durability properties.”
“They should also be part of a wood preservative approval scheme in order to be able to assign correct retention requirements if possible.”
On the creosote front, John Lawrenson, WPA Creosote Group chairman said creosote meets the exclusion recommendations of the Biocidal Regulations – so it could be excluded at some point in the future.
He said it was important the industry gets the right messages to the competent authority in the UK – the Health & Safety Executive. “Most utility companies are trialling alternative materials in their networks because they see a risk that they might not be able to use creosote-treated poles and they might not have an alternative for them,” said Mr Lawrenson.
“It’s important we do not have a gap between creosote becoming unavailable and alternative solutions becoming available. Ultimately it will be the customers who decide what that solution is and we have to do the best we can to help them make that decision.”
The WPA Creosote Group is working hard to manage the transition.
Mr Lawrenson said GRP pole suppliers were claiming an 80-year lifespan for their poles.
Treatment survey
One of the conference highlights was of course the results of the WPA/TTF survey, which WPA technical director Gordon Ewbank said was a chance to generate some real objective data that the WPA can use to formulate an action plan.
The sixty survey respondents included sawmills, preservative suppliers, treaters, importers, distributors and stockists. Quality control was the top issue, with UC4 being the top area of concern and the Industrial Emissions Directive (IED) now proving less important to treaters.
Mr Ewbank said a typical worrying scenario was UC2 imported treated timber going into the distribution chain and ending up being stored as generic “green treated” at a builders merchant yard and then sold as exterior decking joists, which should be a higher Use Class.
“That is a real concern for merchants.” Mr Ewbank said about 500,000m3 of treated wood from Sweden is imported to the UK every year but many UK companies did not understand the NTR Scheme operated by the Swedish Wood Preserving Association and how it relates to the UK market.
He said dialogue is taking place with Sweden about how the WPA and NTR can work together on the issue.
Delegate Mikael Westin, secretary general of the NTR scheme, suggested the problem was in the UK. “If you want quality wood you have to pay for it.”
The big news, announced by WPA director Steve Young, was the WPA looking to give additional strength to its Benchmark QA scheme by giving a UC4 15-year ‘performance assurance’ – a de facto national warranty – to treaters who produce treated wood under the Benchmark scheme.
This, he said, would help leverage Benchmark as a national accreditation scheme.
“This situation of buying UC2 joists from a builders’ yard and using them in a UC3 situation is very real. Supply chain knowledge is something we have to get to grips with. We have to push out of our bubble and get the message across to the audience.”
Mr Young reminded delegates that BS 8417 Preservation of Wood Code of Practice only highlights the minimum penetration and retentions standard.
“There are a lot of treaters in this country who treat to a lot higher specification than that,” he said.
Additional news includes all WPA manuals now being free for members and development of the WPA’s website to include treated wood applications.
A major revision is also being planned for the WPA construction and landscaping manuals.
