Chartered Institute of Building Magazine of the Chartered Institute of Building
  • 19 Feb 2016

Treated hardwoods take on overseas imports

Thermal modification enables UK poplar, sycamore and ash to provide a sustainable alternative.

The first ever range of thermally modified British hardwoods, suitable for hardwearing external applications such as cladding, decking and joinery, will launch at Ecobuild next month.

The super-heated poplar, sycamore and ash varieties are sourced exclusively from English and Welsh woodlands, providing a more sustainable alternative to importing equivalent products from abroad. The treated timber will be marketed under the Brimstone brand.

Tom Barnes, managing director at Vastern Timber, told CM: “Thermally modified softwoods and hardwoods are well established in the market, notably Thermowood from Scandinavia, but there has never been a product that has utilised our own material. Hardwood species make up a large proportion of UK woodlands and are relatively unloved, with very few uses for poplar, sycamore and ash. Thermal modification is an ideal way of bringing them to market.”

Research published in October 2014 by not-for-profit promotion organisation Grown in Britain found that 92% of large contractors would support an industry- wide commitment to use more home- grown timber, and more than 60% said they would add clauses into contracts to encourage its specification.

"Once we bring the thermal modification to this country we complete the environmental story, all wood will be sourced within a hundred mile radius, we will do our own modification and no chemicals are involved."

Tom Barnes, Vastern Timber

Brimstone is the result of a collaboration between Vastern Timber, Grown In Britain, the Building Research Establishment (BRE), Timber Strategies and Tyler Hardwoods. It was established to make British forests more sustainable by identifying new ways to commercialise home-grown timber.

Some funding has also come from the Forestry Commission, and others, to pay for product tests and market research. Although all timber used in Brimstone is sourced in Britain, it must be sent to France to undergo thermal treatment, before being processed to customer requirements in Vastern’s UK sawmill.

However, there are plans to build a thermal modification plant in the UK, if demand is strong enough, for which the BRE has produced a feasibility study.

“The idea of the project is to build up enough demand to attract funding to build a plant in the UK, although clearly we need to develop a market before we can do that,” said Barnes. “Once we bring the thermal modification to this country we complete the environmental story, all wood will be sourced within a hundred mile radius, we will do our own modification and no chemicals are involved.”

Brimstone timber is heated to temperatures of between 160 and 210 degrees C, without the presence of oxygen, improving performance to class 2 durability, equivalent to 30 years’ life – and in some cases class 1 (50 years). This makes it suitable to replace tropical woods, in applications such as cladding, hardwood decking and other external joinery/furniture situations.

However, modification affects the strength of the wood, making it unsuitable for structural applications.

It is also more economic, in some cases, said Barnes: “Put up against similar imported modified hardwoods, like American ash and French ash, the price is comparable, if not cheaper. Depending on which version of Brimstone you go for, it could be cheaper than the tropical hardwood Ipe. The poplar product is cheapest and a similar price to Canadian cedar.”

Recent research indicates that support for UK-grown timber is on the increase. According to the latest statistics from the Forestry Commission, 11.4 million green tonnes of softwood were harvested in 2014, up 5% on 2013, and 0.5 million green tonnes of hardwood, up 1%.

However, the total £1.7bn of wood product exports in 2014 is well below the £7.2bn imported into the UK. The latter figure is also rising, with a 7% increase on 2013.

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