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Engineering works
Published:  24 March, 2010

Finnforest says technical advances are delivering benefits to builders

There is growing demand for I-joists. David Castle reports

Shortages and price increases levied on solid timber last year have led to a gradual switch to I-joists, particularly given that less material is needed in their manufacture. This has also opened up the market to smaller builders and roofing contractors.

And, although Brian Robertson, general manager of James Jones & Sons’ Timber Systems Division, believes that I-joists have probably reached capacity in domestic flooring, he’s seen an increase in the sales of JJI-joists for walls and, particularly, roofs. This, he said, is being driven by the growing interest in the Code for Sustainable Homes.

“Everyone is conscious that Code level 6 will be with us very soon and all the big builders are working towards 2016. We’re talking to a range of major developers, using both timber frame and masonry, who have projects in both the public and private sectors.”

I-joist suppliers say their product offers a number of advantages over its solid rival. These include: stability, both in terms of strength and price; availability in terms of complete pre-cut component packages to site within a matter of days; simplicity and speed of construction; and fewer post-completion performance issues.

And, said Kevin Riley, building solutions director at Finnforest UK, it’s not just about the product. “The technical service, design software and advancement of new build techniques facilitated by the I-joist – this is what is delivering benefits to builders, timber framers and distributors alike,” he said.

Masonite Beams has seen its market grow in the schools, nurse accommodation and nursing home sectors, where the government has pushed green issues along with energy-efficiency requirements. “I-joists remain stable, whether it’s a 160mm or 400mm section,” said Neil Lewis, Masonite Beams UK sales manager.

“Using I-joists in wall and roof applications in the wider sections offers the ability to receive thicker insulations, thus providing extremely energy-efficient buildings with lower U-values. Deep sections allow wider roof spans and can easily accommodate services.”

The proof is already out there. James Jones’ JJI-joists have been used in roofs, walls and floors in the new Scottish Natural Heritage joint offices in Golspie in Sutherland and the company has supplied I-joists for roofs, ceilings and floors for a new bird observatory on Fair Isle.

However, it is the growth in roofs and walls that could be the biggest opportunity for I-joists. Simon Jones, business development manager at Boise Cascade, said his company’s products are being used in a variety of demanding applications. “These can be roofs, from the relatively mundane house attics to vast waveform industrial/commercial projects,” he said. “We also see architects and engineers using I-joists in thick wall applications to maximise the thermal properties of the building envelope.”

Manufacturers aren’t resting on their laurels when it comes to developing their products. Mr Jones said Boise Cascade’s new 32mm-thick Versa-Strand rim board is finding new fans in the timber frame industry and it has launched its EC5 version of BC Calc and BC Framer software to customers.

At James Jones, improvements in material sourcing have yielded timber which is comparable to C30 grade, which the company says gives JJI-joists up to 35% improvement in stiffness, and span gains of up to 254mm at 600mm centres and 355mm at 300mm centres.