There might not be an obvious link between a bridge in Holland, a chair in Germany, and a cricket clubhouse in Edgworth. But, while they might be poles apart in terms of construction, these three structures are pushing the boundaries by using the latest generation of modified timbers.
Big companies are putting money and marketing muscle behind a new breed of timbers, which, thanks to their modification, can offer increased durability, stability and product life, with the added benefit of low maintenance.
When Edgworth Cricket Club briefed designer and builder Rothwell Robinson on its new clubhouse, the main stipulation was that the new building would require little maintenance. Rothwell Robinson chose ThermoWood, a product that combined the performance characteristics the club was after with timber’s aesthetics.
It’s no surprise to Phil Nash, product and specification manager for ThermoWood at Finnforest. “ThermoWood can give a 30-year service life without any treatment being applied,” he said.
Baked wood
ThermoWood is engineered from European redwood and is produced by baking the wood at temperatures exceeding 200OC. The chemical changes that occur during the heating and drying process result in what is said to be a more stable product, and one that Finnforest claims is superior in its resistance to the effects of moisture, insect and fungal decay. This makes it ideal for external applications such as cladding, but it is also very suitable for decking and other landscaping applications.
“We are marketing the product towards national housebuilders, architects and end users,” said Mr Nash. ThermoWood is being used in a new retail park in Bambridge, Northern Ireland, where around 200m3 will be used as external cladding as well as a decorative glulam. Other projects include a Sainsbury’s supermarket at High Wycombe, social housing projects in Norwich and a ‘Sure Start’ children’s centre in Cambridge.
Another thermally-modified timber new to the UK is Plato Wood, a product manufactured in the Netherlands and being marketed in the UK by Ecochoice Ltd. Like ThermoWood, it uses heat for modification but the treatment takes place at lower temperatures. This, claims Ecochoice, provides better results as the end product retains its cell structure and thus all its “good qualities”. These include extreme durability, shape retention, low moisture content, ample bending strength, full treatment and FSC certification.
“The treatment doesn’t include any chemicals,” said Ecochoice managing director Mike Bekin. “The process takes the wood up to 160OC, which causes a chemical reaction inside the wood and the finished wood is more stable and durable than before it entered the kiln. In effect, it has killed the organic matter that would have rotted it over time.”
The main wood being treated is FSC-certified Nordic spruce. While in Europe Plato Wood is proving successful for decorative applications, like cladding, because of its stability (it has a 15-year minimum guarantee), Mr Bekin said it could also be used structurally. The first deal has been signed for its use in the UK, providing external louvres for a small development in London.
UK distributors
Ecochoice is also looking for UK distributors: Palgrave Brown is believed to be the first company to sign up the product. “Plato Wood is positioning itself as a more complex product to its rivals,” said Mr Bekin. “It is much less brittle and consequently can be used for a wider range of applications, including small civil engineering projects and use in harsh, wet environments.”
Osmose’s Indurite is a water-based system which contains a modified natural polysaccharide: put simply, it’s similar to cellulose, which is what the vast proportion of timber comprises.
“Under pressure-impregnation, we put as much of the formulation into the timber as possible: the more permeable the timber, the better effect you will get,” said marketing director Osmose Europe Andy Hodge. “We are trying to create a natural composite; if we are able to fill up the cells with a similar solution to the wood itself, once it’s cured, we end up with denser material.”
This, he said, creates increased hardness and strength improvement and resultant improved dimensional stability. Osmose is also able to change the appearance of the wood: using the Indurite process with more permeable species, it is able to add a pigment which can make a softwood look and perform like a hardwood.
Osmose sees a range of mainly internal uses for Indurite, such as flooring, furniture, doors, decorative panels: any application where a combination of strength, dimensional stability and appearance is essential.
“Research shows that some popular ‘light’ hardwoods don’t perform well as flooring,” said Mr Hodge, “so there is the possibility that we can use Indurite to not only improve the strength of sustainable hardwoods but also on certain types of hardwood.”
The next step, he said, will be looking at its potential for external applications.
BSW Timber is the exclusive supplier for the UK and Ireland of Titan Wood’s Accoya, a product that is already being used in high-profile jobs, such as the 31m bridge being built in northern Holland. This dual carriageway crossover has no restrictions on load, and so a product was needed that delivered high stability and long life. The builders chose Accoya because of its inherent strength and performance characteristics.
Eliminating moisture
Accoya is a chemically-modified softwood, designed to increase the naturally occurring acetyl wood compound. Pine, for example, would normally contain 2% acetyl groups – with Accoya, this is increased to 20%, which prevents moisture from being absorbed.
“By keeping moisture out, we are preventing decay organisms or fungi from attacking the wood,” said BSW Timber’s head of business development John Alexander.
Eliminating the moisture also prevents the wood from shrinking or swelling, or going through big fluctuations in moisture content. Shrinking and swelling also put a high level of exertion on coatings, whether they are opaque paints or translucent wood stains. “If the wood behind the coating is moving out and in, that’s an awful lot of strain, so we are eliminating one of the key causes of premature failure,” said Mr Alexander. This durability means Titan Wood promises much longer lifespans without degradation – at least 50 years when used out of ground. The company is also working with Akzo Nobel Sikkens to develop coatings with longer-life guarantees, up to 12 years when factory-applied.
Titan Wood’s chief executive officer Eddie Pratt said acetylation – the process by which Accoya is created – is the “holy grail” of wood modification. “Although we work with pine species, the end product is so completely different in performance terms that the advice we’ve been given by scientists is to relabel it as a new species.”
Mr Alexander also thinks the timing is right. “There is a better awareness of timber and we believe that we are offering a product that is in line with the eco-assessment tools that are in industry,” he said. The first commercial plant is due to be commissioned in the Netherlands.
Cross-linking cellulose
Others have also joined the fray. Earlier this year, BASF unveiled the first fruits of its new Belmadur technology – a cantilever chair for outdoor use, using shaped beech wood. The company, which has spent e3-5m developing Belmadur, believes the technology will widen the range of applications for species such as pine and beech in flooring, joinery, cladding, decking and garden furniture.
Belmadur is applied to wood by normal pressure impregnation and involves the cross-linking of cellulose molecules within timber. The company claims the process increases the dimensional stability, hardness and durability of wood, making beech as long-lasting as teak and twice as hard as oak. So far, BASF is still investigating the potential of its new technology – but hasn’t ruled out that it could be used for bigger spans.
One company enjoying repeat business for its modified product is Glenalmond Timber, the first licensee and accredited manufacturer of Ultrajoist solid timber joists. Ultrajoist, says the company, is proven to reduce damage and associated costs resulting from timber shrinkage in centrally-heated buildings. The company has developed strict factory conditions to guarantee the environmental and performance characteristics of the joists – wherever they are manufactured.
Glenalmond has supplied Ultrajoists for hundreds of buildings, including 300 houses built by Malcolm Allen of Aberdeen. It has also been used by Prestoplan for upper storey ring beams in timber frame buildings.
“The main benefit for us is not to be regarded as solid timber but as an engineered – or modified – product,” said Glenalmond Timber’s Fraser Steele. “The benefits are that it is pre-shrunk or pre-conditioned so it is not going to move in situ. A lot of timber frame manufacturers are now using Ultrajoist for their top and bottom plates for their panels, because that’s where you get the most differential movement in a building.”
The company is also about to test its flood potential and is looking at incorporating it in a glulam product that could provide spans up to nine metres.
“It gives designers finite parameters to work in rather than sticking their thumb in the air and guessing,” said Mr Steele.
