The engineered wood market is now a mature sector within the UK construction products market and most builders wouldn’t bat an eyelid at the sight of an I-joist or a glulam beam.

But even eyes might be opened now due to a development by US company Louisiana-Pacific (LP), which is currently launching its 225x63mm I-joist in the UK merchanting and small/medium-sized builder market.

LP already serves the national housebuilder/timber frame sectors through its partner Wyder Engineered Timber Systems. Now, LP’s “simply better” business model, through the distributorship of MBM Forest Products, sees small builders opened up to the possibilities and benefits of I-joists, with them being able to pick up as few as one I-joist off-the-shelf from a merchant.

The 225i I-joist, a direct replacement for 8x2in and 9x2 solid timber joists, is part of LP’s SolidStart engineered wood products range and was designed and sized to fit with traditional UK brick and block coursing and to match EU standard glulam depths. 

New LSL products
LP has also developed two new laminated strand lumber (LSL) rim board products to fit the loft conversion and timber frame markets. LP said the new 35x225mm 1.35E LP SolidStart LSL eliminates the need for complicated designs and
expensive reinforcement end details for loft cuts.

In timber frame, LP has determined that its 29mm-thick LSL rim board is the best solution, regarding 32mm, 38mm and 45mm rim as over-specified.

Meanwhile, rival engineered wood brand Steico is changing its range of I-joists. Instead of the top and bottom flanges being made of solid wood, they will now be laminated veneer lumber (LVL).

Steico says the change to Steicoultralam LVL will give a stronger all-round performance as well as combine well with its ultralam LVL rimboards. It says the new combination offered the ability of wider spans for better living space and a more consistent volume production quality compared to solid softwood.

“We believe this core element [I-joist] should not just be the physical loadbearer and control for the shape of the building but an integral part of the insulation envelope,” said Adrian Judd, Steico UK sales manager.

Steico argues that the I-section profile of Steicojoists and Steicowall, which have reduced cross-sections of an 8mm or 6mm web, reduces the capacity for thermal bridging, while insulation depths can be cut through the pre-insulation of the wall studs – usually via the space between the web and the flange filled with wood fibre insulation.

Fire performance testing of fire retardant-treated products in the Steico range is ongoing.

easi-joist sales
Karl Foster, sales and marketing director of Wolf Systems, said sales of the company’s easi-joist open metal web/timber flange joist are up over 50% this year compared with a year ago, with more products being used in different applications rather than just floors.

Wolf is working towards a new Robust Detail for separating floors in apartment buildings. Featuring a recycled product called Iso-rubber, the new floor construction detail is designed to offer quicker installation, reduced labour costs and more flexibility as the overall floor depth is significantly reduced due to the elimination of acoustic battens. Wolf said initial tests show a significant reduction in sound transfer between dwellings, giving extra Code for Sustainable Homes credits.

Meanwhile, a six-month test programme into the use of easi-joist as extra wide timber frame studs for wall construction has concluded. Wolf has previously supplied easi-joist for several projects, but the testing results will lead to a standard specification for manufacturers and designers.

Steico I-joists now have LVL flanges

Structural and thermal test performance data of easi-joist studs with a variety of insulants will be included in a forthcoming technical guide.

Acoustic performance
Acoustic performance has also been a target area for Masonite Beams UK. It claims to be the first I-joist manufacturer to have achieved the sound insulation performance now required for intermediate floors in Scotland, for a system configuration close to current building practice.

Masonite said laboratory testing of an intermediate floor system featuring its I-joists has shown an airborne sound reduction performance of 43dB Rw, meeting the amended Scottish Building Standards' domestic section on noise, 2010 edition. The Sound Research Laboratories testing was carried out in accordance with BS EN ISO 140-3: 1995.

A key standard requirement is an increased sound insulation performance of separating walls and separating floors; and reduced sound passage between rooms in dwellings.

“The results are good news for architects and specifiers of projects in Scotland who are looking for a tried and tested solution for an engineered timber floor system in new build domestic dwellings, but who are struggling to find a cost-effective specification to meet the challenges of the new Building Standards,” said Peter Law, Masonite Beams UK’s technical manager.

Building services
The ability of I-joists to accommodate services such as plumbing is being promoted by Boise Cascade, which has contacted 10,500 industry contacts about its pre-stamped knock-out hole I-joists. The move comes amid increasing demand by housebuilders, main contractors and developers for larger holes to accommodate mechanical ventilation and heat recovery systems.

Boise has also developed its Versa-Bloc detail as a low-cost way to ensure fire resistance at floor level in timber frame party walls. Versa-Bloc provides a sacrificial shield to Boise’s Versa-Lam (LVL) or Versa-Strand OSB rim board, ensuring sufficient structural columns remain at the end of the 60-minute fire resistance period required by Part B of the Building Regulations.

Versa-Bloc is fixed along the rim construction at centres of at least 600mm and allows the rim board to be reduced to a single ply on the party wall. “Close working relationships with our customers allowed us to observe and challenge accepted practice,” said Simon Jones, Boise’s UK business development director.

New projects
Engineered timber construction systems specialist B&K Structures, which uses glulam, cross-laminated timber and structural insulated panels (SIPs), as well as other materials in its projects, has secured five new primary school schemes since last September.

Other projects include the recently-opened Brockholes Wetland Centre for the Lancashire Wildlife Trust and M&S  Cheshire Oaks, where the frame is almost complete. The Brockholes project, designed by Adam Khan Architects, is a floating concrete pontoon with a glulam frame on top, clad with SIPs and oak shingles on the exterior. Mansell is the contractor while engineering is by Price & Myers.

Another recent B&K project – a 60,000ft² Tesco store in Barnstaple – used timber roof cassette technology to eliminate the time-consuming process of building purlins. The 12x2.4m self-spanning cassettes sit on the glulam frame and were installed in just three weeks.

B&K is also in the running for a prestigious project to build a series of new London fire stations. Its hybrid timber/steel solution is currently up against a concrete bid for the job, with a decision expected soon.

B&K Structures’ glulam frame at Brockholes

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