Angus Macfarlane of James Jones & Sons discusses the increasing popularity of I-joists, and their inherent economic, technical and environmental benefits for addressing the current challenges the housebuilding industry faces.
With the Government’s promise to build 300,000 new homes per year to address the current housing shortage, developers are under more pressure than ever before to meet new build targets. Amidst these pressures, developers are also facing environmental challenges as the Government calls for ‘carbon neutral’ homes.
The Zero Carbon Homes Agenda set a range of milestones that the housebuilding industry must meet. It is believed these targets, coupled with the influencing factors of the housebuyer themselves has impacted on the popularity and growth of the use of timber as a prime construction material choice. A recent poll by Public First cited that when those who are considering buying a new-build were asked what factors might influence their views when deciding between two different housebuilders – ‘the respective companies’ environmental credentials was the third most popular answer, only behind ‘reputation for quality work’ and ‘how attractive their homes are.’ The driving force behind this purchasing decision however tended to be motivated by a desire to save money on energy costs rather than wider concerns about the environment.
Nonetheless, these recent government initiatives have encouraged the use of Modern Methods of Construction (MMC) and Off-Site Manufacture (OSM) within the housebuilding industry. It’s believed this has contributed to the existing popularity of specification of the I-joist, as it lends itself well to both construction methods, allowing faster on-site builds and can also be engineered and pre-fabricated in the factory. I-joists possess many technical, installation, economic and environmental benefits, often making them the specification of choice in both modern and traditional housebuilding methods.
To look at the technical benefits initially, I-joists are extremely stable, with an excellent strength-to-weight ratio, and reduce prime costs for building completions. They also lend themselves well to service installation as the OSB or fibreboard can be easily drilled and can even be pre-drilled off-site.
Their economic benefits are particularly appealing to housing developers, as they can be twice as fast to install as traditional methods, and can be supplied as a complete system inclusive of all ancillary items, reducing overall building costs. The well documented skilled labour shortage within the UK construction industry makes the I-joist system even more appealing, as it requires fewer components and therefore introduces less complexity on-site.
I-joists also use less material than solid timber joists to perform the same function, and are a lower embodied energy product when compared to other building materials.
The use of I-joists within panellised roof systems has seen this market innovate and develop rapidly in the UK. Long length joists enable the roof panels to run vertically (as a rafter) or horizontally (as a purlin), in conjunction with glulam (glue-laminated timber) or LVL supports.
However, the inherent product benefits have seen I-joist usage grow not only for roofs and walls but increasingly in flooring systems, making them a market leading solution based on performance, cost and ease of installation.
This increase in usage has led to innovations within the industry, with insulated I-joists being a recent introduction to the marketplace. They offer a much needed benefit where consistent quality, speed and efficiency of manufacture are critical to the supply process.
It’s expected, with reduced energy costs being high on the list of purchasing influences for the house buyer and low carbon homes being high on the political agenda, that the I-joist will continue to be a go-to solution, with more product innovations expected in the near future.
Angus Macfarlane is general manager of James Jones & Sons’ Timber Systems Division